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  • 351. Abrahamsson, Maria
    et al.
    Wolpher, Henriette
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johansson, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Larsson, Jan
    Kritikos, Mikael
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Norrby, Per-Ola
    Bergquist, Jonas
    Sun, Licheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammarström, Leif
    A New Strategy for Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes. Synthesis, Photophysical and Electrochemical characterisation of Six Mononuclear Ruthenium(II) Bisterpyridine Type Complexes2005In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, no 9, p. 3215-3225Article in journal (Refereed)
    Abstract [en]

    The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor−ruthenium−acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifetime of τ = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of τ = 0.25 ns for [Ru(tpy)2]2+. The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)2]2+. Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.

  • 352.
    Abrahamsson, Martin Otto
    et al.
    Stockholm University, Faculty of Social Sciences, School of Business.
    Lavesson, Peter
    Stockholm University, Faculty of Social Sciences, School of Business.
    Tranan - upplevelseekonomi i liten skala2001Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Sammanfattning saknas.

  • 353.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Acquiring L2 Syllable Margins: Studies on the simplification of onsets and codas in interlanguage phonology2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with developmental, universal, grammatical, and functional factors involved in the acquisition of L2 syllable structure. More specifically, using speech data from Spanish and Chinese learners of Swedish, the thesis examines the production and development of syllable onsets and codas—that is, syllable margins. In doing so, the present work draws on various theoretical considerations and empirical findings from research on L1 and L2 acquisition, phonology and phonetics, language variation and language typology. The thesis includes three empirical studies, all of which are based on longitudinal conver­sational data. Study I deals with the acquisition of word-initial /sC(C)/ onsets by one native Spanish speaker, whereas Study II and Study III focus on the acquisi­tion of word-final codas by three native Chinese speakers. Study I and Study II both showed that onset and coda length and phonetic environment are influen­tial factors in the production of syllable structure, while sonority may not be as reliable a predictor of production difficulty. Next, both Study I and Study III provide evidence of a U-shaped rather than linear development of pronunciation accuracy. This pattern is interpreted as an effect of initial increase in fluency, with more focus on content and less on form. In addition, Study III showed that L2 proficiency is related to the epenthesis-deletion differential. An increasing ratio of epenthesis-to-deletion is the first-order indicator of increasing L2 profi­ciency during early stages of acquisition, but increased target-like production becomes the first-order indicator of development at later stages. Finally, Study III showed that learners are aware of potential ambiguity resulting from simpli­fication in different grammatical/functional categories. Codas that are essential for the retention of semantic information are preserved through higher accuracy rates and higher relative levels of epenthesis errors.

  • 354.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Age of onset and nativelike L2 ultimate attainment of morphosyntactic and phonetic intuition2012In: Studies in Second Language Acquisition, ISSN 0272-2631, E-ISSN 1470-1545, Vol. 34, no 2, p. 187-214Article in journal (Refereed)
    Abstract [en]

    Research has consistently shown there is a negative correlation between age of onset (AO) of acquisition and ultimate attainment (UA) of either pronunciation or grammar in a second language (L2). A few studies have indeed reported nativelike behavior in some postpuberty learners with respect to either phonetics/phonology or morphosyntax, a result that has sometimes been taken as evidence against the critical period hypothesis (CPH). However, in the few studies that have employed a wide range of linguistic tests and tasks, adult learners have not exhibited nativelike L2 proficiency across the board of measures, which, according to some, suggests that the hypothesis still holds. The present study investigated the relationship between AO and UA and the incidence of nativelikeness when measures of phonetic and grammatical intuition are combined. An additional aim was to investigate whether children and adults develop the L2 through fundamentally different brain mechanisms-namely, whether children acquire the language (more) implicitly as an interdependent whole, whereas adults learn it (more) explicitly as independent parts of a whole.

  • 355.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Andraspråksinlärning2009Book (Other academic)
    Abstract [en]

    Denna grundbok belyser fenomenet, ämnet och forskningsfältet andraspråksinlärning. Med utgångspunkt i 1960-talets brytning med behavioristisk inlärningspsykologi och kontrastiv språkanalys diskuteras de mest centrala frågeställningarna inom den därefter följande moderna, mentalistiskt orienterade andraspråksforskningen.

    I bokens tio kapitel presenteras de huvudsakliga empiriska upptäckterna och teorierna om andraspråkets utveckling och variation, dess kognition, processning och universella egenskaper, liksom inflödets, interaktionens och undervisningens roll, effekter av sociala och individuella skillnader samt modersmålets inverkan. Många exempel ges från studier av svenska som andraspråk. Boken avslutas med en termordlista med förklaringar till centrala begrepp inom fältet.

    Boken vänder sig främst till universitetsstuderande på grundnivå i ämnen som tvåspråkighet, svenska och nordiska språk samt till blivande och verksamma lärare i svenska som andraspråk och modersmålssvenska.

  • 356.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    But first, let's think again!2018In: Bilingualism: Language and Cognition, ISSN 1366-7289, E-ISSN 1469-1841, Vol. 21, no 5, p. 906-907Article in journal (Refereed)
    Abstract [en]

    On the basis of their review of studies, Mayberry and Kluender (2017) propose that the human language learning ability becomes severely compromised if it is not developed in tandem with brain development in early childhood, but that it functions more or less flawlessly, even in adulthood, if language acquisition had at one time proceeded according to the maturational timetable. Mayberry and Kluender therefore suggest that the critical period hypothesis (CPH) for language is unambiguously tied to the timing of L1 acquisition, but that its relevance to L2 acquisition is less clear, the implication being that the well-documented AoA effects in the SLA literature are due to non-maturational (i.e., psychological, experiential, cross-linguistic, etc.) causes.

  • 357.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Critical Period Hypothesis (CPH)2013In: Routledge Encyclopedia of Second Language Acquisition / [ed] Peter Robinson, London: Routledge, 2013, p. 146-151Chapter in book (Refereed)
  • 358.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Development and recoverability of L2 codas: A longitudinal study of Chinese/Swedish interphonology2003In: Studies in Second Language Acquisition, ISSN 0272-2631, E-ISSN 1470-1545, Vol. 25, no 3, p. 313-349Article in journal (Refereed)
    Abstract [en]

    This study deals with the development and recoverability of word-final codas in Chinese-Swedish interlanguage. The relation between consonant deletion and vowel epenthesis is investigated from both a developmental perspective and a grammatical-functional one. Longitudinal, conversational data from three Chinese beginner learners of Swedish were analyzed. First, it is shown that for these learners the acquisition of Swedish codas was U-shaped rather than linear such that they exhibited relatively high accuracy rates at early stages, lower accuracy rates at later stages, and again high accuracy rates at more advanced stages. It is also demonstrated that the epenthesis-deletion differential is closely related to second language proficiency in that the proportion of epenthesis to deletion errors increases over time. Furthermore, the data show that word-final codas that are relatively important for the retention of semantically relevant information generate lower overall frequencies of simplification and greater epenthesis-deletion proportions than codas containing information that is relatively recoverable from other segments or features in the context.

  • 359.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Development and recoverability of L2 codas: A longitudinal study of Chinese/Swedish interphonology.2001Report (Other academic)
  • 360.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Developmental sequences2013In: Routledge Encyclopedia of Second Language Acquisition / [ed] Peter Robinson, London: Routledge, 2013, p. 173-177Chapter in book (Refereed)
  • 361.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Fonologiska aspekter på andraspråksinlärning och svenska som andraspråk2013In: Svenska som andraspråk: i forskning, undervisning och samhälle / [ed] Hyltenstam, Kenneth & Lindberg, Inger, Lund: Studentlitteratur, 2013, 2. uppl., p. 85-120Chapter in book (Other academic)
  • 362.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Fonologiska aspekter på andraspråksinlärning och svenska som andraspråk2004In: Svenska som andraspråk: i forskning, undervisning och samhälle / [ed] Kenneth Hyltenstam, Inger Lindberg, Lund: Studentlitteratur, 2004, p. 79-116Chapter in book (Other academic)
  • 363.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Natural phonology and second language acquisi­tion: problems and consequences1996In: Toegepaste taalwetenschap in artikelen, ISSN 0169-7420, E-ISSN 2213-4883, no 55, p. 9-22Article in journal (Refereed)
  • 364.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Phonological acquisition2012In: The Encyclopedia of Applied Linguistics / [ed] C. A. Chapelle, Oxford: Wiley-Blackwell, 2012Chapter in book (Refereed)
  • 365.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Review of David Birdsong (ed.): Second Language Acquisition and the Critical Period Hypothesis. Lawrence Erlbaum, 1999.1999In: Applied Linguistics, ISSN 0142-6001, E-ISSN 1477-450X, Vol. 20, no 4, p. 571-575Article, book review (Other academic)
  • 366.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Some observations of child-adult differences in second language pronunciation.1994In: Scandinavian Working Papers on Bilingualism, Vol. 9, p. 1-15Article in journal (Other academic)
  • 367.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Universal constraints on L2 coda production: The case of Chinese/Swedish interphonology2003In: La fonologia dell’interlingua. Principi e metodi di analisi / [ed] Lidia Costamagna, Stefania Giannini, Milano: FrancoAngeli , 2003, p. 131-162Chapter in book (Other academic)
  • 368.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    U-shaped learning and overgeneralization2013In: Routledge Encyclopedia of Second Language Acquisition / [ed] Peter Robinson, London: Routledge, 2013, p. 663-665Chapter in book (Refereed)
  • 369.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Vowel ‘epenthesis’ in the L2 production of L1 Spanish speakers: puzzle or evidence for natural phonology?1997In: New Sounds 97.: Proceedings of the Third Symposium on the Acquisition of Second-Language Speech (University of Klagenfurt, 8-11 September 1997). / [ed] J. Leather & A. James, Klagenfurt: University of Klagenfurt , 1997Conference paper (Other academic)
  • 370.
    Abrahamsson, Niclas
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Vowel epenthesis of /sC(C)/ onsets in Spanish/Swedish inter­phonology: A longitudinal case study1999In: Language learning, ISSN 0023-8333, E-ISSN 1467-9922, Vol. 49, no 3, p. 473-508Article in journal (Refereed)
    Abstract [en]

    Previous studies showed that vowel epenthesis of initial /sC(C)/ clusters in the L2 production of L1 Spanish speakers is conditioned by several variable constraints, such as preceding environment, onset length, and sonority relations among onset members. This case study was designed to investigate whether the patterns obtained from elicited speech also hold for conversational data. A longitudinal corpus of spontaneous/natural speech from 1 adult L1 Spanish learner of L2 Swedish was used. The study confirmed most of the results from previous research, for example, that the frequency of epenthesis varies with preceding phonetic environment. However, the study suggested that a lowering effect of preceding vowels must be present, not just the enhancing effect of preceding consonants suggested by Carlisle (1997).

  • 371.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Bardel, Camilla
    Stockholm University, Faculty of Humanities, Department of Language Education.
    Bartning, Inge
    Stockholm University, Faculty of Humanities, Department of Romance Studies and Classics.
    Erman, Britt
    Stockholm University, Faculty of Humanities, Department of English. English department, Stockholm.
    Fant, Lars
    Stockholm University, Faculty of Humanities, Department of Romance Studies and Classics.
    Forsberg Lundell, Fanny
    Stockholm University, Faculty of Humanities, Department of Romance Studies and Classics.
    Föremålet för inlärning [kap. 3]2014In: avancerad andraspråksanvändning: slutrapport från ett forskningsprogram / [ed] Kenneth Hyltenstam, Inge Bartning, Lars Fant, Göteborg: Makadam Förlag , 2014, no 2, p. 20-46, article id M2005-0459Chapter in book (Refereed)
  • 372.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Bylund, Emanuel
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Andraspråksinlärning och förstaspråksutveckling i en andraspråkskontext2012In: Flerspråkighet – en forskningsöversikt / [ed] Kenneth Hyltenstam, Monica Axelsson, Inger Lindberg, Stockholm: Vetenskapsrådet , 2012, p. 153-246Chapter in book (Refereed)
  • 373.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Age of onset and nativelikeness in a second language: listener perception versus linguistic scrutiny2009In: Language learning, ISSN 0023-8333, E-ISSN 1467-9922, Vol. 59, no 2, p. 249-306Article in journal (Refereed)
  • 374.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Barndomen - en kritisk period för språkutveckling?2010In: Barn utvecklar sitt språk: (2:a reviderade upplagan) / [ed] Louise Bjar och Caroline Liberg, Lund: Studentlitteratur , 2010, 2, p. 29-56Chapter in book (Other academic)
  • 375.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Barndomen – en kritisk period för språkutveck­ling?2003In: Barn utvecklar sitt språk / [ed] Louise Bjar, Caroline Liberg, Lund: Studentlitteratur, 2003, 1. uppl., p. 29-56Chapter in book (Other academic)
  • 376.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Hyltenstam, KennethStockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    High-Level L2 Acquisition, Learning, and Use: Special Issue2012Collection (editor) (Refereed)
  • 377.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Inlärningsålder och uppfattad inföddhet i andraspråket – lyssnarexperiment med avancerade L2-talare av svenska2006In: Nordand: nordisk tidsskrift for andrespråksforskning, ISSN 0809-9227, Vol. 1, no 1, p. 9-36Article in journal (Refereed)
  • 378.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Mognadsbegränsningar och den kritiska perioden för andraspråksinlärning2013In: Svenska som andraspråk: i forskning, undervisning och samhälle / [ed] Hyltenstam, Kenneth & Lindberg, Inger, Lund: Studentlitteratur, 2013, 2. uppl., p. 221-257Chapter in book (Refereed)
  • 379.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Mognadsbegränsningar och den kritiska perioden för andraspråks­inlärning2004In: Svenska som andraspråk: i forskning, undervisning och samhälle / [ed] Kenneth Hyltenstam, Inger Lindberg, Lund: Studentlitteratur, 2004, p. 221-258Chapter in book (Other academic)
  • 380.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Centre for Research on Bilingualism.
    The robustness of aptitude effects in near-native second language acquisition2008In: Studies in Second Language Acquisition, ISSN 0272-2631, E-ISSN 1470-1545, Vol. 30, no 4, p. 481-509Article in journal (Refereed)
    Abstract [en]

    Results from a number of recent studies suggest that nativelike adult second language (L2) learners possess a high degree of language learning aptitude, the positive effects of which may have compensated for the negative effects of a critical period in these learners. According to the same studies, child learners seem to attain a nativelike command of the L2 regardless of high or low aptitude, which has led researchers to conclude that this factor plays no role in early acquisition. The present study investigates the L2 proficiency and language aptitude of 42 near-native L2 speakers of Swedish (i.e., individuals whom actual mother-tongue speakers of Swedish believe are native speakers). The results confirm previous research suggesting that a high degree of language aptitude is required if adult learners are to reach a L2 proficiency that is indistinguishable from that of native speakers. However, in contrast to previous studies, the present results also identify small yet significant aptitude effects in child SLA. Our findings lead us to the conclusions that the rare nativelike adult learners sometimes observed would all turn out to be exceptionally talented language learners with an unusual ability to compensate for maturational effects and, consequently, that their nativelikeness per se does not constitute a reason to reject the critical period hypothesis.

  • 381.
    Abrahamsson, Niclas
    et al.
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Hyltenstam, Kenneth
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Bylund, Emanuel
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism, Centre for Research on Bilingualism.
    Age effects on language acquisition, retention and loss. Key hypotheses and findings2018In: High-Level Language Proficiency in Second Language and Multilingual Contexts / [ed] Kenneth Hyltenstam, Inge Bartning, Lars Fant, Cambridge: Cambridge University Press, 2018, p. 16-49Chapter in book (Refereed)
  • 382.
    Abrahamsson, Åke
    Stockholm University.
    Ljus och frihet till näringsfång: om tidningsväsendet, arbetarrörelsen och det sociala medvetandets ekologi : exemplet Stockholm 1838-18691990Doctoral thesis, monograph (Other academic)
  • 383. Abram, Emese
    et al.
    Gajdatsy, Gabor
    Hermann, Peter
    Ujhelyi, Ferenc
    Borbely, Judit
    Shen, James Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    The colour of monolithic zirconia restorations determined by spectrophotometric examination2019In: Advances in Applied Ceramics: Structural, Functional and Bioceramics, ISSN 1743-6753, E-ISSN 1743-6761, Vol. 118, no 1-2, p. 3-8Article in journal (Refereed)
    Abstract [en]

    Objective: The aim of this in vitro study is to examine the optical effects of monolithic zirconia of different translucency and thickness, combined with substrates of different colours. Materials and methods: Zirconia specimens of two colours (A2P1, WHITE) were used for the study, three try-in pastes (Variolink Esthetic); substrates were prepared from nine types of materials (six VITA SIMULATE, three metals). Measurements were carried out at the Faculty of Atomic Physics of the Technical University of Budapest with the state-of-the-art PerkinElmer (R) Lambda 1050 spectrophotometer. Results: The colouring of zirconia has a major effect on dE values resulting in different colour perceptibility and acceptability. Try-in pastes, however, have no significant effects overall. Conclusion: Applying coloured zirconia is highly eligible for preparing aesthetic crowns as their substrate-covering effect makes it possible to reproduce the desired colour. Uncoloured zirconia nonetheless is unaffected by the substrate material, especially above a certain layer thickness.

  • 384. Abram, Simone
    et al.
    Bianco, B. Feldman
    Khosravi, Shahram
    Stockholm University, Faculty of Social Sciences, Department of Social Anthropology.
    Salazar, N.
    de Genova, N.
    The free movement of people around the world would be Utopian: IUAES World Congress 20132017In: Identities: Global Studies in Culture and Power, ISSN 1070-289X, E-ISSN 1547-3384, Vol. 24, no 2, p. 123-155Article, review/survey (Refereed)
    Abstract [en]

    This article contains the text and discussion of a debate held at the IUAES World Congress in Anthropology at Manchester University in 2013. The motion was proposed by Bela Feldman-Bianco (State University of Campinas), seconded by Noel Salazar (University of Leuven) and was opposed by Shahram Khosravi (Stockholm University), seconded by Nicholas de Genova (then at Goldsmiths' College). The debate was chaired by Simone Abram (Durham University).

  • 385. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anguener, E.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Bissaldi, E.
    Biteau, J.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chalme-Calvet, R.
    Chaves, R. C. G.
    Cheesebrough, A.
    Chretien, M.
    Colafrancesco, S.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Edwards, T.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Goering, D.
    Grondin, M. -H
    Grudzinska, M.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Harris, J.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hervet, O.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Janiak, M.
    Jankowsky, F.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Kieffer, M.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Kolitzus, D.
    Komin, Nu.
    Kosack, K.
    Krakau, S.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemoine-Goumard, M.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Meyer, M.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Murach, T.
    Naumann, C. L.
    de Naurois, M.
    Nedbal, D.
    Niemiec, J.
    Nolan, S. J.
    Oakes, L.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Poon, H.
    Punch, M.
    Quirrenbach, A.
    Raab, S.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schuessler, F.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sol, H.
    Spengler, G.
    Spiess, F.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorster, M.
    Wagner, S. J.
    Wagner, P.
    Ward, M.
    Weidinger, M.
    White, R.
    Wierzcholska, A.
    Willmann, P.
    Woernlein, A.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9-1854062013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 554, p. A72-Article in journal (Refereed)
    Abstract [en]

    The detection of the high-frequency peaked BL Lac object (HBL) SHBL J001355.9-185406 (z = 0.095) at high (HE; 100 MeV < E < 300 GeV) and very high-energy (VHE; E > 100 GeV) with the Fermi Large Area Telescope (LAT) and the High Energy Stereoscopic System (H.E.S.S.) is reported. Dedicated observations were performed with the H. E. S. S. telescopes, leading to a detection at the 5.5 sigma significance level. The measured flux above 310 GeV is (8.3 +/- 1.7(stat) +/- 1.7(sys)) x 10(-13) photons cm(-2) s(-1) (about 0.6% of that of the Crab Nebula), and the power-law spectrum has a photon index of Gamma = 3.4 +/- 0.5(stat) +/- 0.2(sys). Using 3.5 years of publicly available Fermi-LAT data, a faint counterpart has been detected in the LAT data at the 5.5 sigma significance level, with an integrated flux above 300 MeV of (9.3 +/- 3.4(stat) +/- 0.8(sys)) x 10(-10) photons cm(-2) s(-1) and a photon index of Gamma = 1.96 +/- 0.20(stat) +/- 0.08(sys). X-ray observations with Swift-XRT allow the synchrotron peak energy in vF(v) representation to be located at similar to 1.0 keV. The broadband spectral energy distribution is modelled with a one-zone synchrotron self-Compton (SSC) model and the optical data by a black-body emission describing the thermal emission of the host galaxy. The derived parameters are typical of HBLs detected at VHE, with a particle-dominated jet.

  • 386. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anguener, E.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Bissaldi, E.
    Biteau, J.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chalme-Calvet, R.
    Chaves, R. C. G.
    Cheesebrough, A.
    Chretien, M.
    Colafrancesco, S.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Edwards, T.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Goering, D.
    Grondin, M-H
    Grudzinska, M.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Harris, J.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hervet, O.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Janiak, M.
    Jankowsky, F.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Kieffer, M.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Kolitzus, D.
    Komin, Nu.
    Kosack, K.
    Krakau, S.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemoine-Goumard, M.
    Lenain, J-P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C-C
    Marandon, V.
    Marcowith, A.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Meyer, M.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Murach, T.
    Naumann, C. L.
    de Naurois, M.
    Nedbal, D.
    Niemiec, J.
    Nolan, S. J.
    Oakes, L.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P-O
    Peyaud, B.
    Pita, S.
    Poon, H.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raab, S.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schuessler, F.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sol, H.
    Spengler, G.
    Spiess, F.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J-P
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorster, M.
    Wagner, S. J.
    Wagner, P.
    Ward, M.
    Weidinger, M.
    White, R.
    Wierzcholska, A.
    Willmann, P.
    Woernlein, A.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H-S
    Perkins, J. S.
    Ojha, R.
    Stevens, J.
    Edwards, P. G.
    Kadler, M.
    HESS and Fermi-LAT discovery of gamma-rays from the blazar 1ES 1312-4232013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 434, no 3, p. 1889-1901Article in journal (Refereed)
    Abstract [en]

    A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of gamma-rays from the blazar 1ES 1312-423, 2 degrees away from the radio galaxy. With a differential flux at 1 TeV of phi(1 TeV) = (1.9 +/- 0.6(stat) +/- 0.4(sys)) x 10(-13) cm(-2) s(-1) TeV-1 corresponding to 0.5 per cent of the Crab nebula differential flux and a spectral index Gamma = 2.9 +/- 0.5(stat) +/- 0.2(sys), 1ES 1312-423 is one of the faintest sources ever detected in the very high energy (E > 100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi Large Area Telescope (Fermi-LAT) data allows the discovery at high energies (E > 100 MeV) of a hard spectrum (Gamma = 1.4 +/- 0.4(stat) +/- 0.2(sys)) source coincident with 1ES 1312-423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self-Compton model for the non-thermal component, combined with a blackbody spectrum for the optical emission from the host galaxy.

  • 387. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Becker, J.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Buesching, I.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Gerard, L.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nguyen, N.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Identification of HESS J1303-631 as a pulsar wind nebula through gamma-ray, X-ray, and radio observations2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 548, p. A46-Article in journal (Refereed)
    Abstract [en]

    Aims. The previously unidentified very high-energy (VHE; E > 100 GeV) gamma-ray source HESS J1303-631, discovered in 2004, is re-examined including new data from the H. E. S. S. Cherenkov telescope array in order to identify this object. Archival data from the XMM-Newton X-ray satellite and from the PMN radio survey are also examined. Methods. Detailed morphological and spectral studies of VHE gamma-ray emission as well as of the XMM-Newton X-ray data are performed. Radio data from the PMN survey are used as well to construct a leptonic model of the source. The gamma-ray and X-ray spectra and radio upper limit are used to construct a one zone leptonic model of the spectral energy distribution (SED). Results. Significant energy-dependent morphology of the gamma-ray source is detected with high-energy emission (E > 10 TeV) positionally coincident with the pulsar PSR J1301-6305 and lower energy emission (E < 2 TeV) extending similar to 0.4 degrees to the southeast of the pulsar. The spectrum of the VHE source can be described with a power-law with an exponential cut-off N-0 = (5.6 +/- 0.5) x 10(-12) TeV-1 cm(-2) s(-1), Gamma = 1.5 +/- 0.2) and E-cut = (7.7 +/- 2.2) TeV. The pulsar wind nebula (PWN) is also detected in X-rays, extending similar to 2-3' from the pulsar position towards the center of the gamma-ray emission region. A potential radio counterpart from the PMN survey is also discussed, showing a hint for a counterpart at the edge of the X-ray PWN trail and is taken as an upper limit in the SED. The extended X-ray PWN has an unabsorbed flux of F2-10 (keV) similar to 1.6(-0.4)(+0.2) x 10(-13) erg cm(-2)s(-1) and is detected at a significance of 6.5 sigma. The SED is well described by a one zone leptonic scenario which, with its associated caveats, predicts a very low average magnetic field for this source. Conclusions. Significant energy-dependent morphology of this source, as well as the identification of an associated X-ray PWN from XMM-Newton observations enable identification of the VHE source as an evolved PWN associated to the pulsar PSR J1301-6305. This identification is supported by the one zone leptonic model, which suggests that the energetics of the gamma-ray and X-ray radiation are such that they may have a similar origin in the pulsar nebula. However, the large discrepancy in emission region sizes and the low level of synchrotron radiation suggest a multi-population leptonic nature. The low implied magnetic field suggests that the PWN has undergone significant expansion. This would explain the low level of synchrotron radiation and the difficulty in detecting counterparts at lower energies, the reason this source was originally classified as a dark VHE gamma-ray source.

  • 388. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Becker, J.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Buesching, I.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, H. J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Gerard, L.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu.
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nguyen, N.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Ali, M. O.
    Constraints on the gamma ray emission from the cluster scale agn outburst in the hydra a galaxy cluster2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 545, p. A103-Article in journal (Refereed)
    Abstract [en]

    Context. In some galaxy clusters, powerful active galactic nuclei (AGN) have blown bubbles with cluster scale extent into the ambient medium. The main pressure support of these bubbles is not known to date, but cosmic rays are a viable possibility. For such a scenario copious gamma-ray emission is expected as a tracer of cosmic rays from these systems. Aims. Hydra A, the closest galaxy cluster hosting a cluster scale AGN outburst, located at a redshift of 0.0538, is investigated for being a gamma-ray emitter with the High Energy Stereoscopic System (H.E.S.S.) array and the Fermi Large Area Telescope (Fermi-LAT). Methods. Data obtained in 20.2 h of dedicated H. E. S. S. observations and 38 months of Fermi-LAT data, gathered by its usual all-sky scanning mode, have been analyzed to search for a gamma-ray signal. Results. No signal has been found in either data set. Upper limits on the gamma-ray flux are derived and are compared to models. These are the first limits on gamma-ray emission ever presented for galaxy clusters hosting cluster scale AGN outbursts. Conclusions. The non-detection of Hydra A in gamma-rays has important implications on the particle populations and physical conditions inside the bubbles in this system. For the case of bubbles mainly supported by hadronic cosmic rays, the most favorable scenario, which involves full mixing between cosmic rays and embedding medium, can be excluded. However, hadronic cosmic rays still remain a viable pressure support agent to sustain the bubbles against the thermal pressure of the ambient medium. The largest population of highly-energetic electrons, which are relevant for inverse-Compton gamma-ray production is found in the youngest inner lobes of Hydra A. The limit on the inverse-Compton gamma-ray flux excludes a magnetic field below half of the equipartition value of 16 mu G in the inner lobes.

  • 389. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Becker, J.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Gerard, L.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    de Jager, O. C.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu.
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P.
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C.
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nguyen, N.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O.
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P.
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S.
    Discovery of gamma-ray emission from the extragalactic pulsar wind nebula N 157B with HESS2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 545, article id L2Article in journal (Refereed)
    Abstract [en]

    We present the significant detection of the first extragalactic pulsar wind nebula (PWN) detected in gamma rays, N 157B, located in the large Magellanic Cloud (LMC). Pulsars with high spin-down luminosity are found to power energised nebulae that emit gamma rays up to energies of several tens of TeV. N 157B is associated with PSR J0537-6910, which is the pulsar with the highest known spin-down luminosity. The High Energy Stereoscopic System telescope array observed this nebula on a yearly basis from 2004 to 2009 with a dead-time corrected exposure of 46 h. The gamma-ray spectrum between 600 GeV and 12 TeV is well-described by a pure power-law with a photon index of 2.8 +/- 0.2(stat) +/- 0.3(syst) and a normalisation at 1 TeV of (8.2 +/- 0.8(stat) +/- 2.5(syst)) x 10(-13) cm(-2) s(-1) TeV-1. A leptonic multi-wavelength model shows that an energy of about 4 x 10(49) erg is stored in electrons and positrons. The apparent efficiency, which is the ratio of the TeV gamma-ray luminosity to the pulsar's spin-down luminosity, 0.08% +/- 0.01%, is comparable to those of PWNe found in the Milky Way. The detection of a PWN at such a large distance is possible due to the pulsar's favourable spin-down luminosity and a bright infrared photon-field serving as an inverse-Compton-scattering target for accelerated leptons. By applying a calorimetric technique to these observations, the pulsar's birth period is estimated to be shorter than 10 ms.

  • 390. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Behera, B.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chaves, R. C. G.
    Cheesebrough, A.
    Colafrancesco, S.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foester, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goeing, D.
    Grondin, M. -H
    Grudzinska, M.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu.
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemoine-Goumard, M.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nguyen, N.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raab, S.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. S.
    HESS discovery of VHE gamma-rays from the quasar PKS 1510-0892013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 554, p. A107-Article in journal (Refereed)
    Abstract [en]

    The quasar PKS 1510-089 (z = 0.361) was observed with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes during high states in the optical and GeV bands, to search for very high energy (VHE, defined as E >= 0.1 TeV) emission. VHE gamma-rays were detected with a statistical significance of 9.2 standard deviations in 15.8 h of H. E. S. S. data taken during March and April 2009. A VHE integral flux of I(0.15 TeV < E < 1.0TeV) = (1.0 +/- 0.2(stat) +/- 0.2(sys)) x 10(-11) cm(-2) s(-1) is measured. The best-fit power law to the VHE data has a photon index of G = 5.4 +/- 0.7(stat) +/- 0.3(sys). The GeV and optical light curves show pronounced variability during the period of H.E.S.S. observations. However, there is insufficient evidence to claim statistically significant variability in the VHE data. Because of its relatively high redshift, the VHE flux from PKS 1510-089 should suffer considerable attenuation in the intergalactic space due to the extragalactic background light (EBL). Hence, the measured gamma-ray spectrum is used to derive upper limits on the opacity due to EBL, which are found to be comparable with the previously derived limits from relatively-nearby BL Lac objects. Unlike typical VHE-detected blazars where the broadband spectrum is dominated by nonthermal radiation at all wavelengths, the quasar PKS 1510-089 has a bright thermal component in the optical to UV frequency band. Among all VHE detected blazars, PKS 1510-089 has the most luminous broad line region. The detection of VHE emission from this quasar indicates a low level of gamma - gamma absorption on the internal optical to UV photon field.

  • 391. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubois, F.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C-C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nguyen, N.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Probing the extent of the non-thermal emission from the Vela X region at TeV energies with HESS2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 548, p. A38-Article in journal (Refereed)
    Abstract [en]

    Context. Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae, and associated with the energetic Vela pulsar (PSR B0833-45). Extended very-high-energy (VHE) gamma-ray emission (HESS J0835-455) was discovered using the H. E. S. S. experiment in 2004. The VHE gamma-ray emission was found to be coincident with a region of X-ray emission discovered with ROSAT above 1.5 keV (the so-called Vela X cocoon): a filamentary structure extending southwest from the pulsar to the centre of Vela X. Aims. A deeper observation of the entire Vela X nebula region, also including larger offsets from the cocoon, has been performed with H. E. S. S. This re-observation was carried out in order to probe the extent of the non-thermal emission from the Vela X region at TeV energies and to investigate its spectral properties. Methods. To increase the sensitivity to the faint gamma-ray emission from the very extended Vela X region, a multivariate analysis method combining three complementary reconstruction techniques of Cherenkov-shower images is applied for the selection of gamma-ray events. The analysis is performed with the On/Off background method, which estimates the background from separate observations pointing away from Vela X; towards regions free of gamma-ray sources but with comparable observation conditions. Results. The gamma-ray surface brightness over the large Vela X region reveals that the detection of non-thermal VHE gamma-ray emission from the PWN HESS J0835-455 is statistically significant over a region of radius 1.2 degrees around the position alpha = 08(h)35(m)00(s), delta = -45 degrees 36'00 '' (J2000). The Vela X region exhibits almost uniform gamma-ray spectra over its full extent: the differential energy spectrum can be described by a power-law function with a hard spectral index Gamma = 1.32 +/- 0.06(stat) +/- 0.12(sys) and an exponential cutoff at an energy of (14.0 +/- 1.6(stat) +/- 2.6(sys)) TeV. Compared to the previous H. E. S. S. observations of Vela X the new analysis confirms the general spatial overlap of the bulk of the VHE gamma-ray emission with the X-ray cocoon, while its extent and morphology appear more consistent with the (more extended) radio emission, contradicting the simple correspondence between VHE gamma-ray and X-ray emissions. Morphological and spectral results challenge the interpretation of the origin of gamma-ray emission in the GeV and TeV ranges in the framework of current models.

  • 392. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu.
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nguyen, N.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Measurement of the extragalactic background light imprint on the spectra of the brightest blazars observed with HESS2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 550, p. A4-Article in journal (Refereed)
    Abstract [en]

    The extragalactic background light (EBL) is the diffuse radiation with the second highest energy density in the Universe after the cosmic microwave background. The aim of this study is the measurement of the imprint of the EBL opacity to.-rays on the spectra of the brightest extragalactic sources detected with the High Energy Stereoscopic System (H. E. S. S.). The originality of the method lies in the joint fit of the EBL optical depth and of the intrinsic spectra of the sources, assuming intrinsic smoothness. Analysis of a total of similar to 10(5) gamma-ray events enables the detection of an EBL signature at the 8.8 sigma level and constitutes the first measurement of the EBL optical depth using very-high energy (E > 100 GeV) gamma-rays. The EBL flux density is constrained over almost two decades of wavelengths [0.30 mu m, 17 mu m] and the peak value at 1.4 mu m is derived as lambda F-lambda = 15 +/- 2(stat) +/- 3(sys) nW m(-2) sr(-1).

  • 393. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chaves, R. C. G.
    Cheesebrough, A.
    Colafrancesco, S.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M-H
    Grudzinska, M.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Kolitzus, D.
    Komin, Nu.
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemoine-Goumard, M.
    Lenain, J-P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C-C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nguyen, N.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    de Ona Wilhelmi, E.
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P-O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raab, S.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J-P
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H-S
    Search for very-high-energy gamma-ray emission from Galactic globular clusters with HESS2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 551, p. A26-Article in journal (Refereed)
    Abstract [en]

    Context. Globular clusters (GCs) are established emitters of high-energy (HE, 100 MeV < E < 100 GeV) gamma-ray radiation which could originate from the cumulative emission of the numerous millisecond pulsars (msPSRs) in the clusters' cores or from inverse Compton (IC) scattering of relativistic leptons accelerated in the GC environment. These stellar clusters could also constitute a new class of sources in the very-high-energy (VHE, E > 100 GeV) gamma-ray regime, judging from the recent detection of a signal from the direction of Terzan 5 with the H.E.S.S. telescope array. Aims. To search for VHE gamma-ray sources associated with other GCs, and to put constraints on leptonic emission models, we systematically analyzed the observations towards 15 GCs taken with the H. E. S. S. array of imaging atmospheric Cherenkov telescopes. Methods. We searched for point-like and extended VHE gamma-ray emission from each GC in our sample and also performed a stacking analysis combining the data from all GCs to investigate the hypothesis of a population of faint emitters. Assuming IC emission as the origin of the VHE gamma-ray signal from the direction of Terzan 5, we calculated the expected gamma-ray flux from each of the 15 GCs, based on their number of millisecond pulsars, their optical brightness and the energy density of background photon fields. Results. We did not detect significant VHE gamma-ray emission from any of the 15 GCs in either of the two analyses. Given the uncertainties related to the parameter determinations, the obtained flux upper limits allow to rule out the simple IC/msPSR scaling model for NGC6388 and NGC7078. The upper limits derived from the stacking analyses are factors between 2 and 50 below the flux predicted by the simple leptonic scaling model, depending on the assumed source extent and the dominant target photon fields. Therefore, Terzan 5 still remains exceptional among all GCs, as the VHE gamma-ray emission either arises from extra-ordinarily efficient leptonic processes, or from a recent catastrophic event, or is even unrelated to the GC itself.

  • 394. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chaves, R. C. G.
    Cheesebrough, A.
    Colafrancesco, S.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fussling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemoine-Goumard, M.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nguyen, N.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Awilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Search for Photon-Linelike Signatures from Dark Matter Annihilations with H.E.S.S.2013In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, no 4, p. 041301-Article in journal (Refereed)
    Abstract [en]

    Gamma-ray line signatures can be expected in the very-high-energy (E-gamma > 100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical gamma-ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H. E. S. S. gamma-ray instrument, upper limits on linelike emission are obtained in the energy range between similar to 500 GeV and similar to 25 TeV for the central part of the Milky Way halo and for extragalactic observations, complementing recent limits obtained with the Fermi-LAT instrument at lower energies. No statistically significant signal could be found. For monochromatic gamma-ray line emission, flux limits of (2 x 10(-7)-2 x 10(-5)) m(-2)s(-1)sr(-1) and (1 x 10(-8)- 2 x 10(-6)) m(-2)s(-1)sr(-1) are obtained for the central part of the Milky Way halo and extragalactic observations, respectively. For a DM particle mass of 1 TeV, limits on the velocity- averaged DM annihilation cross section <sigma upsilon >(chi chi ->gamma gamma) reach similar to 10(-27)cm(3)s(-1), based on the Einasto parametrization of the Galactic DM halo density profile. 

  • 395. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chaves, R. C. G.
    Cheesebrough, A.
    Colafrancesco, S.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Grudzinska, M.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Kolitzus, D.
    Komin, Nu
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemoine-Goumard, M.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Menzler, U.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nguyen, N.
    Niemiec, J.
    Nolan, S. J.
    Oakes, L.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raab, S.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Willmann, P.
    Wouters, D.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    HESS observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 551, p. A94-Article in journal (Refereed)
    Abstract [en]

    Aims. We present very high energy (VHE; E > 100 GeV) data from the gamma-ray binary system PSR B1259-63/LS 2883 taken around its periastron passage on 15th of December 2010 with the High Energy Stereoscopic System (H. E. S. S.) of Cherenkov Telescopes. We aim to search for a possible TeV counterpart of the GeV flare detected by the Fermi LAT. In addition, we aim to study the current periastron passage in the context of previous observations taken at similar orbital phases, testing the repetitive behaviour of the source. Methods. Observations at VHEs were conducted with H.E.S.S. from 9th to 16th of January 2011. The total dataset amounts to similar to 6 h of observing time. The data taken around the 2004 periastron passage were also re-analysed with the current analysis techniques in order to extend the energy spectrum above 3 TeV to fully compare observation results from 2004 and 2011. Results. The source is detected in the 2011 data at a significance level of 11.5 sigma revealing an averaged integral flux above 1 TeV of (1.01 +/- 0.18(stat) +/- 0.20(sys)) x 10(-12) cm(-2) s(-1). The differential energy spectrum follows a power-law shape with a spectral index Gamma = 2.92 +/- 0.30(stat) +/- 0.20(sys) and a flux normalisation at 1 TeV of N-0 = (1.95 +/- 0.32(stat) +/- 0.39(sys)) x 10(-12) TeV-1 cm(-2) s(-1). The measured light curve does not show any evidence for variability of the source on the daily scale. The re-analysis of the 2004 data yields results compatible with the published ones. The differential energy spectrum measured up to similar to 10 TeV is consistent with a power law with a spectral index Gamma = 2.81 +/- 0.10(stat) +/- 0.20(sys) and a flux normalisation at 1 TeV of N-0 = (1.29 +/- 0.08(stat) +/- 0.26(sys)) x 10(-12) TeV-1 cm(-2) s(-1). Conclusions. The measured integral flux and the spectral shape of the 2011 data are compatible with the results obtained around previous periastron passages. The absence of variability in the H.E.S.S. data indicates that the GeV flare observed by Fermi LAT in the time period covered also by H.E.S.S. observations originates in a different physical scenario than the TeV emission. Moreover, the comparison of the new results to the results from the 2004 observations made at a similar orbital phase provides a stronger evidence of the repetitive behaviour of the source.

  • 396. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Becker, J.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Buesching, I.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, J.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Degrange, B.
    Deil, C.
    Dickinson, H. J.
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gallant, Y. A.
    Gast, H.
    Gerard, L.
    Gerbig, D.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    de Jager, O. C.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Keogh, D.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu.
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P.
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C.
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nguyen, N.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O.
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Rayner, S. M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, J.
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P.
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S.
    Discovery of VHE gamma-ray emission and multi-wavelength observations of the BL Lacertae object 1RXSJ101015.9-3119092012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 542, article id A94Article in journal (Refereed)
    Abstract [en]

    1RXS J101015.9-311909 is a galaxy located at a redshift of z = 0.14 hosting an active nucleus (called AGN) belonging to the class of bright BL Lac objects. Observations at high (HE, E > 100 MeV) and very high (VHE, E > 100 GeV) energies provide insights into the origin of very energetic particles present in such sources and the radiation processes at work. We report on results from VHE observations performed between 2006 and 2010 with the H. E. S. S. instrument, an array of four imaging atmospheric Cherenkov telescopes. H. E. S. S. data have been analysed with enhanced analysis methods, making the detection of faint sources more significant. VHE emission at a position coincident with 1RXS J101015.9-311909 is detected with H. E. S. S. for the first time. In a total good-quality livetime of about 49 h, we measure 263 excess counts, corresponding to a significance of 7.1 standard deviations. The photon spectrum above 0.2 TeV can be described by a power-law with a photon index of Gamma = 3.08 +/- 0.42(stat) +/- 0.20(sys). The integral flux above 0.2 TeV is about 0.8% of the flux of the Crab nebula and shows no significant variability over the time reported. In addition, public Fermi/LAT data are analysed to search for high energy emission from the source. The Fermi/LAT HE emission in the 100 MeV to 200 GeV energy range is significant at 8.3 standard deviations in the chosen 25-month dataset. UV and X-ray contemporaneous observations with the Swift satellite in May 2007 are also reported, together with optical observations performed with the atom telescope located at the H. E. S. S. site. Swift observations reveal an absorbed X-ray flux of F(0.3-7) keV = 1.04(-0.05)(+0.04) x 10(-11) erg cm(-2) s(-1) in the 0.3-7 keV range. Finally, all the available data are used to study the multi-wavelength properties of the source. The spectral energy distribution (SED) can be reproduced using a simple one-zone Synchrotron Self Compton (SSC) model with emission from a region with a Doppler factor of 30 and a magnetic field between 0.025 and 0.16 G. These parameters are similar to those obtained for other sources of this type.

  • 397. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Becker, J.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Buesching, I.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Gerard, L.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nguyen, N.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    SPECTRAL ANALYSIS AND INTERPRETATION OF THE gamma-RAY EMISSION FROM THE STARBURST GALAXY NGC 2532012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 757, no 2, p. 158-Article in journal (Refereed)
    Abstract [en]

    Very high energy (VHE; E >= 100 GeV) and high-energy (HE; 100 MeV <= E <= 100 GeV) data from gamma-ray observations performed with the H. E. S. S. telescope array and the Fermi-LAT instrument, respectively, are analyzed in order to investigate the non-thermal processes in the starburst galaxy NGC 253. The VHE gamma-ray data can be described by a power law in energy with differential photon index Gamma = 2.14 +/- 0.18(stat) +/- 0.30(sys) and differential flux normalization at 1 TeV of F-0 = (9.6 +/- 1.5(stat)(+5.7, -2.9)(sys)) x 10(-14) TeV-1 cm(-2) s(-1). A power-law fit to the differential HE gamma-ray spectrum reveals a photon index of Gamma = 2.24 +/- 0.14(stat) +/- 0.03(sys) and an integral flux between 200 MeV and 200 GeV of F(0.2-200 GeV) = (4.9 +/- 1.0(stat) +/- 0.3(sys)) x 10(-9) cm(-2) s(-1). No evidence for a spectral break or turnover is found over the dynamic range of both the LAT instrument and the H.E.S.S. experiment: a combined fit of a power law to the HE and VHE gamma-ray data results in a differential photon index Gamma = 2.34 +/- 0.03 with a p-value of 30%. The gamma-ray observations indicate that at least about 20% of the energy of the cosmic rays (CRs) capable of producing hadronic interactions is channeled into pion production. The smooth alignment between the spectra in the HE and VHE gamma-ray domain suggests that the same transport processes dominate in the entire energy range. Advection is most likely responsible for charged particle removal from the starburst nucleus from GeV to multiple TeV energies. In a hadronic scenario for the gamma-ray production, the single overall power-law spectrum observed would therefore correspond to the mean energy spectrum produced by the ensemble of CR sources in the starburst region.

  • 398. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Becker, J.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Buesching, I.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, Hugh
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O ' C
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gallant, Y. A.
    Gast, H.
    Gerard, L.
    Gerbig, D.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    de Jager, O. C.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Keogh, D.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nguyen, N.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Rayner, S. M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Discovery of VHE emission towards the Carina arm region with the HESS telescope array: HESSJ1018-5892012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 541, p. A5-Article in journal (Refereed)
    Abstract [en]

    The Carina arm region, containing the supernova remnant SNRG284.3-1.8, the high-energy (HE; E > 100 MeV) binary 1FGL J1018.6-5856 and the energetic pulsar PSRJ1016-5857 and its nebula, has been observed with the H. E. S. S. telescope array. The observational coverage of the region in very-high-energy (VHE; E > 0.1TeV) gamma-rays benefits from deep exposure (40 h) of the neighboring open cluster Westerlund 2. The observations have revealed a new extended region of VHE gamma-ray emission. The new VHE source HESS J1018-589 shows a bright, point-like emission region positionally coincident with SNRG284.3-1.8 and 1FGL J1018.6-5856 and a diffuse extension towards the direction of PSRJ1016-5857. A soft (Gamma = 2.7 +/- 0.5(stat)) photon index, with a differential flux at 1 TeV of N-0 = (4.2 +/- 1.1) x 10(-13) TeV-1 cm(-2) s(-1) is found for the point-like source, whereas the total emission region including the diffuse emission region is well fit by a power-law function with spectral index Gamma = 2.9 +/- 0.4(stat) and differential flux at 1 TeV of N-0 = (6.8 +/- 1.6) x 10(-1)3 TeV-1 cm(-2) s(-1). This H. E. S. S. detection motivated follow-up X-ray observations with the XMM-Newton satellite to investigate the origin of the VHE emission. The analysis of the XMM-Newton data resulted in the discovery of a bright, non-thermal point-like source (XMMU J101855.4-58564) with a photon index of Gamma = 1.65 +/- 0.08 in the center of SNRG284.3-1.8, and a thermal, extended emission region coincident with its bright northern filament. The characteristics of this thermal emission are used to estimate the plasma density in the region as n approximate to 0.5 cm(-3) (2.9 kpc/d)(2). The position of XMMUJ101855.4-58564 is compatible with the position reported by the Fermi-LAT collaboration for the binary system 1FGL J1018.6-5856 and the variable Swift XRT source identified with it. The new X-ray data are used alongside archival multi-wavelength data to investigate the relationship between the VHE gamma-ray emission from HESS J1018-589 and the various potential counterparts in the Carina arm region.

  • 399. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balzer, A.
    Barnacka, A.
    Becherini, Y.
    Becker, J.
    Bernloehr, K.
    Birsin, E.
    Biteau, J.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Buesching, I.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gallant, Y. A.
    Garrigoux, T.
    Gast, H.
    Gerard, L.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goering, D.
    Grondin, M. -H
    Haeffner, S.
    Hague, J. D.
    Hahn, J.
    Hampf, D.
    Harris, J.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu.
    Kosack, K.
    Kossakowski, R.
    Krayzel, F.
    Laffon, H.
    Lamanna, G.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nguyen, N.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sheidaei, F.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Terrier, R.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    White, R.
    Wierzcholska, A.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    Montmerle, T.
    HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae2012In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 424, no 1, p. 128-135Article in journal (Refereed)
    Abstract [en]

    The massive binary system Eta Carinae and the surrounding H ii complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E= 100 GeV) ?-ray emission could be expected. This paper presents data collected during VHE ?-ray observations with the HESS telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-h data set no hint of significant ?-ray emission from Eta Carinae has been found and an upper limit on the ?-ray flux of (99 per cent confidence level) is derived above the energy threshold of 470 GeV. Together with the detection of high energy (HE; 0.1 =E= 100 GeV) ?-ray emission by the Fermi Large Area Telescope up to 100 GeV, and assuming a continuation of the average HE spectral index into the VHE domain, these results imply a cut-off in the ?-ray spectrum between the HE and VHE ?-ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe ?? absorption losses in the wind collision region. Furthermore, the search for extended ?-ray emission from the Carina nebula resulted in an upper limit on the ?-ray flux of (99 per cent confidence level). The derived upper limit of 23 on the cosmic ray enhancement factor is compared with results found for the old-age mixed-morphology supernova remnant W28.

  • 400. Abramowski, A.
    et al.
    Acero, F.
    Aharonian, F.
    Akhperjanian, A. G.
    Anton, G.
    Balzer, A.
    Barnacka, A.
    de Almeida, U. Barres
    Bazer-Bachi, A. R.
    Becherini, Y.
    Becker, J.
    Behera, B.
    Bernloehr, K.
    Bochow, A.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Borrel, V.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Buesching, I.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Chounet, L. -M
    Clapson, A. C.
    Coignet, G.
    Colom, P.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, Hugh J.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O. 'C.
    Dubois, F.
    Dubus, G.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Fallon, L.
    Farnier, C.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gallant, Y. A.
    Gast, H.
    Gerard, L.
    Gerbig, D.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goret, P.
    Goering, D.
    Haeffner, S.
    Hague, J. D.
    Hampf, D.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hinton, J. A.
    Hoffmann, A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    de Jager, O. C.
    Jahn, C.
    Jamrozy, M.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Keogh, D.
    Khangulyan, D.
    Khelifi, B.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Komin, Nu
    Kosack, K.
    Kossakowski, R.
    Laffon, H.
    Lamanna, G.
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C-C
    Marandon, V.
    Marcowith, A.
    Masbou, J.
    Maurin, D.
    Maxted, N.
    McComb, T. J. L.
    Medina, M. C.
    Mehault, J.
    Nguyen, N.
    Moderski, R.
    Moulin, E.
    Naumann, C. L.
    Naumann-Godo, M.
    de Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Nicholas, B.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Olive, J-F
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Panter, M.
    Arribas, M. Paz
    Pedaletti, G.
    Pelletier, G.
    Petrucci, P-O
    Pita, S.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raue, M.
    Rayner, S. M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Ripken, Joachim
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Ruppel, J.
    Ryde, F.
    Sahakian, V.
    Santangelo, A.
    Schlickeiser, R.
    Schoeck, F. M.
    Schoenwald, A.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Shalchi, A.
    Sikora, M.
    Skilton, J. L.
    Sol, H.
    Spengler, G.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J-P
    Terrier, R.
    Tibolla, O.
    Tluczykont, M.
    Valerius, K.
    van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Vialle, J. P.
    Viana, A.
    Vincent, P.
    Vivier, M.
    Voelk, H. J.
    Volpe, F.
    Vorobiov, S.
    Vorster, M.
    Wagner, S. J.
    Ward, M.
    Wierzcholska, A.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H-S
    Burnett, T. H.
    Hill, A. B.
    HESS J1943+213: a candidate extreme BL Lacertae object2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 529, p. A49-Article in journal (Refereed)
    Abstract [en]

    Context. The H. E. S. S. Cherenkov telescope array has been surveying the Galactic plane for new VHE (>100 GeV) gamma-ray sources. Aims. We report on a newly detected point-like source, HESS J1943+213. This source coincides with an unidentified hard X-ray source IGR J19443+2117, which was proposed to have radio and infrared counterparts. Methods. We combine new H. E. S. S., Fermi/LAT and Nancay Radio Telescope observations with pre-existing non-simultaneous multi-wavelength observations of IGR J19443+2117 and discuss the likely source associations as well as the interpretation as an active galactic nucleus, a gamma-ray binary or a pulsar wind nebula. Results. HESS J1943+213 is detected at the significance level of 7.9 sigma (post-trials) at RA(J2000) = 19(h)43(m)55(s) +/- 1(stat)(s) +/- 1(sys)(s), Dec(J2000) = +21 degrees 18'8 '' +/- 17(stat)'' +/- 20(sys)''. The source has a soft spectrum with photon index Gamma = 3.1 +/- 0.3(stat) +/- 0.2(sys) and a flux above 470 GeV of (1.3 +/- 0.2(stat) +/- 0.3(sys)) x 10(-12) cm(-2) s(-1). There is no Fermi/LAT counterpart down to a flux limit of 6 x 10(-9) cm(-2) s(-1) in the 0.1-100 GeV energy range (95% confidence upper limit calculated for an assumed power-law model with a photon index Gamma = 2.0). The data from radio to VHE gamma-rays do not show any significant variability. Conclusions. The lack of a massive stellar counterpart disfavors the binary hypothesis, while the soft VHE spectrum would be very unusual in case of a pulsar wind nebula. In addition, the distance estimates for Galactic counterparts places them outside of the Milky Way. All available observations favor an interpretation as an extreme, high-frequency peaked BL Lac object with a redshift z > 0.14. This would be the first time a blazar is detected serendipitously from ground-based VHE observations, and the first VHE AGN detected in the Galactic Plane.

567891011 351 - 400 of 104676
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