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Publications (10 of 53) Show all publications
De Angelis, A., Tatischeff, V., Grenier, I. A., McEnery, J., Mallamaci, M., Tavani, M., . . . Zoglauer, A. (2018). Science with e-ASTROGAM A space mission for MeV-GeV gamma-ray astrophysics. Journal of High Energy Astrophysics, 19, 1-106
Open this publication in new window or tab >>Science with e-ASTROGAM A space mission for MeV-GeV gamma-ray astrophysics
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2018 (English)In: Journal of High Energy Astrophysics, ISSN 2214-4048, E-ISSN 2214-4056, Vol. 19, p. 1-106Article in journal (Refereed) Published
Abstract [en]

e-ASTROGAM ('enhanced ASTROGAM') is a breakthrough Observatory space mission, with a detector composed by a Silicon tracker, a calorimeter, and an anticoincidence system, dedicated to the study of the non-thermal Universe in the photon energy range from 0.3 MeV to 3 GeV - the lower energy limit can be pushed to energies as low as 150 keV for the tracker, and to 30 keV for calorimetric detection. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their effects on the surroundings. With a line sensitivity in the MeV energy range one to two orders of magnitude better than previous generation instruments, e-ASTROGAM will determine the origin of key isotopes fundamental for the understanding of supernova explosion and the chemical evolution of our Galaxy. The mission will provide unique data of significant interest to a broad astronomical community, complementary to powerful observatories such as LIGO-Virgo-GEO600-KAGRA, SKA, ALMA, E-ELT, TMT, LSST, JWST, Athena, CTA, IceCube, KM3NeT, and LISA.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-162952 (URN)10.1016/j.jheap.2018.07.001 (DOI)000449510800001 ()2-s2.0-85054709790 (Scopus ID)
Available from: 2018-12-13 Created: 2018-12-13 Last updated: 2023-01-25Bibliographically approved
Ackermann, M., Ajello, M., Atwood, W. B., Baldini, L., Ballet, J., Barbiellini, G., . . . Zimmer, S. (2016). 2FHL: THE SECOND CATALOG OF HARD FERMI-LAT SOURCES. Astrophysical Journal Supplement Series, 222(1), Article ID 5.
Open this publication in new window or tab >>2FHL: THE SECOND CATALOG OF HARD FERMI-LAT SOURCES
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2016 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 222, no 1, article id 5Article in journal (Refereed) Published
Abstract [en]

We present a catalog of sources detected above 50 GeV by the Fermi-Large Area Telescope (LAT) in 80 months of data. The newly delivered Pass. 8 event-level analysis allows the detection and characterization of sources in the 50 GeV-2 TeV energy range. In this energy band, Fermi-LAT. has detected 360 sources, which constitute the second catalog of hard Fermi-LAT. sources (2FHL). The improved angular resolution enables the precise localization of point sources (similar to 1.' 7 radius at 68% C.L.) and the detection and characterization of spatially extended sources. We find that 86% of the sources can be associated with counterparts at other wavelengths, of which the majority (75%) are active galactic nuclei and the rest (11%) are Galactic sources. Only 25% of the 2FHL sources have been previously detected by Cherenkov telescopes, implying that the 2FHL provides a reservoir of candidates to be followed up at very high energies. This work closes the energy gap between the observations performed at GeV energies by Fermi-LAT. on orbit and the observations performed at higher energies by Cherenkov telescopes from the ground.

Keywords
catalogs, gamma-rays: general
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-127288 (URN)10.3847/0067-0049/222/1/5 (DOI)000368982300005 ()2-s2.0-84955482407 (Scopus ID)
Available from: 2016-06-28 Created: 2016-03-01 Last updated: 2022-10-17Bibliographically approved
Acero, F., Ackermann, M., Ajello, M., Albert, A., Baldini, L., Ballet, J., . . . Zimmer, S. (2016). DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA. Astrophysical Journal Supplement Series, 223(2), Article ID 26.
Open this publication in new window or tab >>DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA
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2016 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 223, no 2, article id 26Article in journal (Refereed) Published
Abstract [en]

Most of the celestial. rays detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point-source and extended-source studies rely on the modeling of this diffuse emission for accurate characterization. Here, we describe the development of the Galactic Interstellar Emission Model (GIEM), which is the standard adopted by the LAT Collaboration and is publicly available. This model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse-Compton emission produced in the Galaxy. In the GIEM, we also include large-scale structures like Loop. I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20 degrees and we observe an enhanced emission toward their base extending in the north and south Galactic directions and located within similar to 4 degrees of the Galactic Center.

Keywords
gamma rays: diffuse background, gamma rays: general, gamma rays: ISM
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-130885 (URN)10.3847/0067-0049/223/2/26 (DOI)000375304600008 ()2-s2.0-84964712053 (Scopus ID)
Available from: 2016-06-07 Created: 2016-06-07 Last updated: 2022-10-17Bibliographically approved
Ajello, M., Albert, A., Atwood, W. B., Barbiellini, G., Bastieri, D., Bechtol, K., . . . Zimmer, S. (2016). FERMI-LAT OBSERVATIONS OF HIGH-ENERGY gamma-RAY EMISSION TOWARD THE GALACTIC CENTER. Astrophysical Journal, 819(1), Article ID 44.
Open this publication in new window or tab >>FERMI-LAT OBSERVATIONS OF HIGH-ENERGY gamma-RAY EMISSION TOWARD THE GALACTIC CENTER
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2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 819, no 1, article id 44Article in journal (Refereed) Published
Abstract [en]

The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy gamma-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a 15 degrees x 15 degrees region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the.-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner similar to 1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15 degrees x 15 degrees region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point Source Catalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with gamma-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.

Keywords
cosmic rays, Galaxy: center, gamma-rays: general, gamma-rays: ISM, radiation mechanisms: non-thermal
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-129626 (URN)10.3847/0004-637X/819/1/44 (DOI)000372303400044 ()2-s2.0-84960950940 (Scopus ID)
Available from: 2016-04-29 Created: 2016-04-26 Last updated: 2022-10-17Bibliographically approved
Ackermann, M., Ajello, M., Albert, A., Anderson, B., Arimoto, M., Atwood, W. B., . . . Zimmer, S. (2016). FERMI-LAT OBSERVATIONS OF THE LIGO EVENT GW150914. Astrophysical Journal Letters, 823(1), Article ID L2.
Open this publication in new window or tab >>FERMI-LAT OBSERVATIONS OF THE LIGO EVENT GW150914
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2016 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 823, no 1, article id L2Article in journal (Refereed) Published
Abstract [en]

The Fermi Large Area Telescope (LAT) has an instantaneous field of view (FoV) covering similar to 1/5 of the sky and it completes a survey of the entire sky in high-energy gamma-rays every 3 hr. It enables searches for transient phenomena over timescales from milliseconds to years. Among these phenomena could be electromagnetic counterparts to gravitational wave (GW) sources. In this paper, we present a detailed study of the LAT observations relevant to Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150914, which is the first direct detection of gravitational waves and has been interpreted as being due to the coalescence of two stellar-mass black holes. The localization region for GW150914 was outside the LAT FoV at the time of the GW signal. However, as part of routine survey observations, the LAT observed the entire LIGO localization region within similar to 70 minutes of the trigger and thus enabled a comprehensive search for a.-ray counterpart to GW150914. The study of the LAT data presented here did not find any potential counterparts to GW150914, but it did provide limits on the presence of a transient counterpart above 100 MeV on timescales of hours to days over the entire GW150914 localization region.

Keywords
gamma-ray burst: general, gamma-rays: general, gravitational waves, methods: observational
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-132069 (URN)10.3847/2041-8205/823/1/L2 (DOI)000376391700002 ()2-s2.0-84971611975 (Scopus ID)
Available from: 2016-07-12 Created: 2016-07-06 Last updated: 2022-10-17Bibliographically approved
Anderson, B., Meyer, M., Ferretti, R., Sollerman, J., Zimmer, S. & Rosswog, S. (2016). LOCALIZATION AND BROADBAND FOLLOW-UP OF THE GRAVITATIONAL-WAVE TRANSIENT GW 150914. Astrophysical Journal Letters, 826(1), Article ID L13.
Open this publication in new window or tab >>LOCALIZATION AND BROADBAND FOLLOW-UP OF THE GRAVITATIONAL-WAVE TRANSIENT GW 150914
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2016 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 826, no 1, article id L13Article in journal (Refereed) Published
Abstract [en]

A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline, and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams.

Keywords
gravitational waves, methods: observational
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-168068 (URN)10.3847/2041-8205/826/1/L13 (DOI)000380739300013 ()2-s2.0-84982731665 (Scopus ID)
Available from: 2019-05-24 Created: 2019-05-24 Last updated: 2022-10-17Bibliographically approved
Ackermann, M., Ajello, M., Albert, A., Atwood, W. B., Baldini, L., Ballet, J., . . . Rephaeli, Y. (2016). Search for gamma-ray emission from the Coma Cluster with six years of Fermi-LAT data. Astrophysical Journal, 819(2), Article ID 149.
Open this publication in new window or tab >>Search for gamma-ray emission from the Coma Cluster with six years of Fermi-LAT data
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2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 819, no 2, article id 149Article in journal (Refereed) Published
Abstract [en]

We present results from gamma-ray observations of the Coma cluster incorporating six years of Fermi-LAT data and the newly released "Pass 8" event-level analysis. Our analysis of the region reveals low-significance residual structures within the virial radius of the cluster that are too faint for a detailed investigation with the current data. Using a likelihood approach that is free of assumptions on the spectral shape we derive upper limits on the gamma-ray flux that is expected from energetic particle interactions in the cluster. We also consider a benchmark spatial and spectral template motivated by models in which the observed radio halo is mostly emission by secondary electrons. In this case, the median expected and observed upper limits for the flux above 100MeV are 1.7 x 10(-9) ph cm(-2) s(-1) and 5.2 x 10(-9) ph cm(-2) s(-1) respectively (the latter corresponds to residual emission at the level of 1.8 sigma). These bounds are comparable to or higher than predicted levels of hadronic gamma-ray emission in cosmic-ray (CR) models with or without reacceleration of secondary electrons, although direct comparisons are sensitive to assumptions regarding the origin and propagation mode of CRs and magnetic field properties. The minimal expected.-ray flux from radio and star-forming galaxies within the Coma cluster is roughly an order of magnitude below the median sensitivity of our analysis.

Keywords
galaxies: clusters: individual (Coma), gamma rays: galaxies: clusters
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-121584 (URN)10.3847/0004-637X/819/2/149 (DOI)000372305700061 ()2-s2.0-84961123614 (Scopus ID)
Available from: 2015-10-10 Created: 2015-10-10 Last updated: 2022-10-18Bibliographically approved
Anderson, B., Zimmer, S., Conrad, J., Gustafsson, M., Sánchez-Conde, M. & Caputo, R. (2016). Search for Gamma-ray Lines Towards Galaxy Clusters with the Fermi-LAT. Journal of Cosmology and Astroparticle Physics (2), Article ID 026.
Open this publication in new window or tab >>Search for Gamma-ray Lines Towards Galaxy Clusters with the Fermi-LAT
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2016 (English)In: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, no 2, article id 026Article in journal (Refereed) Published
Abstract [en]

We report on a search for monochromatic gamma-ray features in the spectra of galaxy clusters observed by the Fermi Large Area Telescope. Galaxy clusters are the largest structures in the Universe that are bound by dark matter (DM), making them an important testing ground for possible self-interactions or decays of the DM particles. Monochromatic gamma-ray lines provide a unique signature due to the absence of astrophysical backgrounds and are as such considered a smoking-gun signature for new physics. An unbinned joint likelihood analysis of the sixteen most promising clusters using five years of data at energies between 10 and 400 GeV revealed no significant features. For the case of self-annihilation, we set upper limits on the monochromatic velocity-averaged interaction cross section. These limits are compatible with those obtained from observations of the Galactic Center, albeit weaker due to the larger distance to the studied clusters.

Keywords
dark matter experiments, galaxy clusters, gamma ray experiments
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-121585 (URN)10.1088/1475-7516/2016/02/026 (DOI)000372467600027 ()2-s2.0-84961169928 (Scopus ID)
Available from: 2015-10-10 Created: 2015-10-10 Last updated: 2023-03-28Bibliographically approved
Ajello, M., Albert, A., Anderson, B., Baldini, L., Barbiellini, G., Bastieri, D., . . . Zimmer, S. (2016). Search for Spectral Irregularities due to Photon-Axionlike-Particle Oscillations with the Fermi Large Area Telescope. Physical Review Letters, 116(16), Article ID 161101.
Open this publication in new window or tab >>Search for Spectral Irregularities due to Photon-Axionlike-Particle Oscillations with the Fermi Large Area Telescope
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2016 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, no 16, article id 161101Article in journal (Refereed) Published
Abstract [en]

We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the gamma-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area Telescope data, we find no evidence for ALPs and exclude couplings above 5 x 10(-12) GeV-1 for ALP masses 0.5 less than or similar to m(a) less than or similar to 5 neV at 95% confidence. The limits are competitive with the sensitivity of planned laboratory experiments, and, together with other bounds, strongly constrain the possibility that ALPs can reduce the gamma-ray opacity of the Universe.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-130872 (URN)10.1103/PhysRevLett.116.161101 (DOI)000374559300002 ()27152783 (PubMedID)2-s2.0-84964467037 (Scopus ID)
Available from: 2016-06-09 Created: 2016-06-07 Last updated: 2022-10-18Bibliographically approved
Charles, E., Sánchez-Conde, M., Anderson, B., Caputo, R., Cuoco, A., Di Mauro, M., . . . Razzano, M. (2016). Sensitivity projections for dark matter searches with the Fermi large area telescope. Physics reports, 636, 1-46
Open this publication in new window or tab >>Sensitivity projections for dark matter searches with the Fermi large area telescope
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2016 (English)In: Physics reports, ISSN 0370-1573, E-ISSN 1873-6270, Vol. 636, p. 1-46Article, review/survey (Refereed) Published
Abstract [en]

The nature of dark matter is a longstanding enigma of physics; it may consist of particles beyond the Standard Model that are still elusive to experiments. Among indirect search techniques, which look for stable products from the annihilation or decay of dark matter particles, or from axions coupling to high-energy photons, observations of the gamma-ray sky have come to prominence over the last few years, because of the excellent sensitivity of the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope mission. The LAT energy range from 20 meV to above 300 GeV is particularly well suited for searching for products of the interactions of dark matter particles. In this report we describe methods used to search for evidence of dark matter with the LAT, and review the status of searches performed with up to six years of LAT data. We also discuss the factors that determine the sensitivities of these searches, including the magnitudes of the signals and the relevant backgrounds, considering both statistical and systematic uncertainties. We project the expected sensitivities of each search method for 10 and 15 years of LAT data taking. In particular, we find that the sensitivity of searches targeting dwarf galaxies, which provide the best limits currently, will improve faster than the square root of observing time. Current LAT limits for dwarf galaxies using six years of data reach the thermal relic level for masses up to 120 GeV for the b (b) over bar annihilation channel for reasonable dark matter density profiles. With projected discoveries of additional dwarfs, these limits could extend to about 250 GeV. With as much as 15 years of LAT data these searches would be sensitive to dark matter annihilations at the thermal relic cross section for masses to greater than 400 GeV (200 GeV) in the b (b) over bar(tau(+)tau(-)) annihilation channels.

Keywords
Gamma-ray observations, Dark matter, Fermi-LAT
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-168080 (URN)10.1016/j.physrep.2016.05.001 (DOI)000378190200001 ()2-s2.0-84969651434 (Scopus ID)
Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2022-10-18Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-5735-0082

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