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Moskalenko, I. V.ORCID iD iconorcid.org/0000-0001-6141-458x
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Publications (10 of 12) Show all publications
Baldini, L., Ballet, J., Bastieri, D., Becerra Gonzalez, J., Bellazzini, R., Berretta, A., . . . Zaharijas, G. (2021). Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data. Astrophysical Journal Supplement Series, 256(1), Article ID 13.
Open this publication in new window or tab >>Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data
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2021 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 256, no 1, article id 13Article in journal (Refereed) Published
Abstract [en]

We present the first Fermi Large Area Telescope (LAT) catalog of long-term gamma-ray transient sources (1FLT). This comprises sources that were detected on monthly time intervals during the first decade of Fermi-LAT operations. The monthly timescale allows us to identify transient and variable sources that were not yet reported in other Fermi-LAT catalogs. The monthly data sets were analyzed using a wavelet-based source detection algorithm that provided the candidate new transient sources. The search was limited to the extragalactic regions of the sky to avoid the dominance of the Galactic diffuse emission at low Galactic latitudes. The transient candidates were then analyzed using the standard Fermi-LAT maximum likelihood analysis method. All sources detected with a statistical significance above 4 sigma in at least one monthly bin were listed in the final catalog. The 1FLT catalog contains 142 transient gamma-ray sources that are not included in the 4FGL-DR2 catalog. Many of these sources (102) have been confidently associated with active galactic nuclei (AGNs): 24 are associated with flat-spectrum radio quasars, 1 with a BL Lac object, 70 with blazars of uncertain type, 3 with radio galaxies, 1 with a compact steep-spectrum radio source, 1 with a steep-spectrum radio quasar, and 2 with AGNs of other types. The remaining 40 sources have no candidate counterparts at other wavelengths. The median gamma-ray spectral index of the 1FLT-AGN sources is softer than that reported in the latest Fermi-LAT AGN general catalog. This result is consistent with the hypothesis that detection of the softest gamma-ray emitters is less efficient when the data are integrated over year-long intervals.
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-198238 (URN)10.3847/1538-4365/ac072a (DOI)000692874900001 ()
Available from: 2021-11-08 Created: 2021-11-08 Last updated: 2022-03-07Bibliographically approved
Ajello, M., Atwood, W. B., Axelsson, M., Bagagli, R., Bagni, M., Baldini, L., . . . Zaharijas, G. (2021). Fermi Large Area Telescope Performance after 10 Years of Operation. Astrophysical Journal Supplement Series, 256(1), Article ID 12.
Open this publication in new window or tab >>Fermi Large Area Telescope Performance after 10 Years of Operation
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2021 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 256, no 1, article id 12Article in journal (Refereed) Published
Abstract [en]

The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10 yr milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories.
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-198243 (URN)10.3847/1538-4365/ac0ceb (DOI)000692877400001 ()2-s2.0-85115774062 (Scopus ID)
Available from: 2021-11-08 Created: 2021-11-08 Last updated: 2022-11-10Bibliographically approved
Ajello, M., Arimoto, M., Axelsson, M., Baldini, L., Barbiellini, G., Bastieri, D., . . . Zimmer, S. (2019). A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog. Astrophysical Journal, 878(1), Article ID 52.
Open this publication in new window or tab >>A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog
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2019 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 878, no 1, article id 52Article in journal (Refereed) Published
Abstract [en]

The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present the second catalog of LAT-detected GRBs, covering the first 10 yr of operations, from 2008 to 2018 August 4. A total of 186 GRBs are found; of these, 91 show emission in the range 30-100 MeV (17 of which are seen only in this band) and 169 are detected above 100 MeV. Most of these sources were discovered by other instruments (Fermi/GBM, Swift/BAT, AGILE, INTEGRAL) or reported by the Interplanetary Network (IPN); the LAT has independently triggered on four GRBs. This catalog presents the results for all 186 GRBs. We study onset, duration, and temporal properties of each GRB, as well as spectral characteristics in the 100 MeV-100 GeV energy range. Particular attention is given to the photons with the highest energy. Compared with the first LAT GRB catalog, our rate of detection is significantly improved. The results generally confirm the main findings of the first catalog: the LAT primarily detects the brightest GBM bursts, and the high-energy emission shows delayed onset as well as longer duration. However, in this work we find delays exceeding 1 ks and several GRBs with durations over 10 ks. Furthermore, the larger number of LAT detections shows that these GRBs not only cover the high-fluence range of GBM-detected GRBs but also sample lower fluences. In addition, the greater number of detected GRBs with redshift estimates allows us to study their properties in both the observer and rest frames. Comparison of the observational results with theoretical predictions reveals that no model is currently able to explain all results, highlighting the role of LAT observations in driving theoretical models.
Keywords
catalogs, gamma-ray burst: general, methods: data analysis
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-170852 (URN)10.3847/1538-4357/ab1d4e (DOI)000471624300001 ()2-s2.0-85069507025 (Scopus ID)
Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2022-11-02Bibliographically approved
Jóhannesson, G., Porter, T. A. & Moskalenko, I. (2019). Cosmic-Ray Propagation in Light of the Recent Observation of Geminga. Astrophysical Journal, 879(2), Article ID 91.
Open this publication in new window or tab >>Cosmic-Ray Propagation in Light of the Recent Observation of Geminga
2019 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 879, no 2, article id 91Article in journal (Refereed) Published
Abstract [en]

The High Altitude Water Cherenkov (HAWC) telescope recently observed extended emission around the Geminga and PSR. B0656+14 pulsar wind nebulae (PWNe). These observations have been used to estimate cosmic-ray (CR) diffusion coefficients near the PWNe that appear to be more than two orders of magnitude smaller than the diffusion coefficients typically derived for the interstellar medium from measured abundances of secondary species in CRs. Two-zone diffusion models have been proposed as a solution to this discrepancy, where the slower diffusion zone (SDZ) is confined to a small region around the PWN. Such models are shown to successfully reproduce the HAWC observations of the Geminga PWN while retaining consistency with other CR data. It is found that the size of the SDZ influences the predicted positron flux and the spectral shape of the extended gamma-ray emission at lower energies that can be observed with the Fermi Large Area Telescope. If the two observed PWNe are not unique, then it is likely that there are similar pockets of slow diffusion around many CR sources elsewhere in the Milky Way. The consequences of such a picture for Galactic CR propagation is explored.
Keywords
astroparticle physics, cosmic rays, diffusion, Galaxy: structure, gamma rays: diffuse background, gamma rays: ISM
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-171748 (URN)10.3847/1538-4357/ab258e (DOI)000474921300007 ()
Available from: 2019-09-06 Created: 2019-09-06 Last updated: 2022-02-26Bibliographically approved
Boschini, M. J., Della Torre, S., Gervasi, M., Grandi, D., Jóhannesson, G., La Vacca, G., . . . Tacconi, M. (2018). HelMod in the Works: From Direct Observations to the Local Interstellar Spectrum of Cosmic-Ray Electrons. Astrophysical Journal, 854(2), Article ID 94.
Open this publication in new window or tab >>HelMod in the Works: From Direct Observations to the Local Interstellar Spectrum of Cosmic-Ray Electrons
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2018 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 854, no 2, article id 94Article in journal (Refereed) Published
Abstract [en]

The local interstellar spectrum (LIS) of cosmic-ray (CR) electrons for the energy range 1 MeV to 1 TeV is derived using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HELMOD, are combined to provide a single framework that is run to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. An iterative maximum-likelihood method is developed that uses GALPROP-predicted LIS as input to HELMOD, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The optimized HelMod parameters are then used to adjust GALPROP parameters to predict a refined LIS with the procedure repeated subject to a convergence criterion. The parameter optimization uses an extensive data set of proton spectra from 1997 to 2015. The proposed CR electron LIS accommodates both the low-energy interstellar spectra measured by Voyager 1 as well as the high-energy observations by PAMELA and AMS-02 that are made deep in the heliosphere; it also accounts for Ulysses counting rate features measured out of the ecliptic plane. The interstellar and heliospheric propagation parameters derived in this study agree well with our earlier results for CR protons, helium nuclei, and anti-protons propagation and LIS obtained in the same framework.
Keywords
cosmic rays, diffusion, elementary particles, interplanetary medium, ISM: general, Sun: heliosphere
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-154583 (URN)10.3847/1538-4357/aaa75e (DOI)000425306100017 ()
Available from: 2018-04-06 Created: 2018-04-06 Last updated: 2022-02-26Bibliographically approved
Ackermann, M., Ajello, M., Asano, K., Baldini, L., Barbiellini, G., Baring, M. G., . . . Littlejohns, O. (2013). MULTIWAVELENGTH OBSERVATIONS OF GRB 110731A: GeV EMISSION FROM ONSET TO AFTERGLOW. Astrophysical Journal, 763(2), Article ID 71.
Open this publication in new window or tab >>MULTIWAVELENGTH OBSERVATIONS OF GRB 110731A: GeV EMISSION FROM ONSET TO AFTERGLOW
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2013 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 763, no 2, article id 71Article in journal (Refereed) Published
Abstract [en]

We report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for which simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. The observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Gamma similar to 500-550.
Keywords
gamma-ray burst: individual (GRB110731A)
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-161706 (URN)10.1088/0004-637X/763/2/71 (DOI)000313869800002 ()2-s2.0-84872690981 (Scopus ID)
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2023-12-06Bibliographically approved
Ackermann, M., Ajello, M., Atwood, W. B., Baldini, L., Barbiellini, G., Bastieri, D., . . . Zimmer, S. (2012). CONSTRAINTS ON THE GALACTIC HALO DARK MATTER FROM FERMI-LAT DIFFUSE MEASUREMENTS. Astrophysical Journal, 761(2), Article ID 91.
Open this publication in new window or tab >>CONSTRAINTS ON THE GALACTIC HALO DARK MATTER FROM FERMI-LAT DIFFUSE MEASUREMENTS
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2012 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 761, no 2, article id 91Article in journal (Refereed) Published
Abstract [en]

We have performed an analysis of the diffuse gamma-ray emission with the Fermi Large Area Telescope (LAT) in the Milky Way halo region, searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints are presented. We consider both gamma rays produced directly in the dark matter annihilation/decay and produced by inverse Compton scattering of the e(+)/e(-) produced in the annihilation/decay. Conservative limits are derived requiring that the dark matter signal does not exceed the observed diffuse gamma-ray emission. A second set of more stringent limits is derived based on modeling the foreground astrophysical diffuse emission using the GALPROP code. Uncertainties in the height of the diffusive cosmic-ray halo, the distribution of the cosmic-ray sources in the Galaxy, the index of the injection cosmic-ray electron spectrum, and the column density of the interstellar gas are taken into account using a profile likelihood formalism, while the parameters governing the cosmic-ray propagation have been derived from fits to local cosmic-ray data. The resulting limits impact the range of particle masses over which dark matter thermal production in the early universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as the annihilation of dark matter.
Keywords
dark matter, Galaxy: halo, gamma rays: diffuse background, methods: statistical
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-161716 (URN)10.1088/0004-637X/761/2/91 (DOI)000312090300010 ()2-s2.0-84870842972 (Scopus ID)
Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2024-03-01Bibliographically approved
Ackermann, M., Ajello, M., Albert, A., Baldini, L., Barbiellini, G., Bechtol, K., . . . Zimmer, S. (2012). Fermi LAT search for dark matter in gamma-ray lines and the inclusive photon spectrum. Physical Review D: covering particles, fields, gravitation, and cosmology, 86(2), Article ID 022002.
Open this publication in new window or tab >>Fermi LAT search for dark matter in gamma-ray lines and the inclusive photon spectrum
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2012 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 86, no 2, article id 022002Article in journal (Refereed) Published
Abstract [en]

Dark matter particle annihilation or decay can produce monochromatic gamma-ray lines and contribute to the diffuse gamma-ray background. Flux upper limits are presented for gamma-ray spectral lines from 7 to 200 GeV and for the diffuse gamma-ray background from 4.8 GeV to 264 GeV obtained from two years of Fermi Large Area Telescope data integrated over most of the sky. We give cross-section upper limits and decay lifetime lower limits for dark matter models that produce gamma-ray lines or contribute to the diffuse spectrum, including models proposed as explanations of the PAMELA and Fermi cosmic-ray data.
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-162402 (URN)10.1103/PhysRevD.86.022002 (DOI)000306193000001 ()2-s2.0-84863837831 (Scopus ID)
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2022-09-30Bibliographically approved
Ackermann, M., Ajello, M., Allafort, A., Baldini, L., Ballet, J., Bastieri, D., . . . Yang, Z. (2012). GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THE FERMI LARGE AREA TELESCOPE. Astrophysical Journal, 755(2), Article ID 164.
Open this publication in new window or tab >>GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THE FERMI LARGE AREA TELESCOPE
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2012 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 755, no 2, article id 164Article in journal (Refereed) Published
Abstract [en]

Recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that galaxies rapidly forming massive stars are more luminous at gamma-ray energies compared to their quiescent relatives. Building upon those results, we examine a sample of 69 dwarf, spiral, and luminous and ultraluminous infrared galaxies at photon energies 0.1-100 GeV using 3 years of data collected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). Measured fluxes from significantly detected sources and flux upper limits for the remaining galaxies are used to explore the physics of cosmic rays in galaxies. We find further evidence for quasi-linear scaling relations between gamma-ray luminosity and both radio continuum luminosity and total infrared luminosity which apply both to quiescent galaxies of the Local Group and low-redshift starburst galaxies (conservative P-values less than or similar to 0.05 accounting for statistical and systematic uncertainties). The normalizations of these scaling relations correspond to luminosity ratios of log(L0.1-100GeV/L-1.4GHz) = 1.7 +/- 0.1((statistical)) +/- 0.2((dispersion)) and log(L0.1-100GeV/L8-1000 (mu m)) = -4.3 +/- 0.1((statistical)) +/- 0.2((dispersion)) for a galaxy with a star formation rate of 1 M-circle dot yr(-1), assuming a Chabrier initial mass function. Using the relationship between infrared luminosity and gamma-ray luminosity, the collective intensity of unresolved star-forming galaxies at redshifts 0 < z < 2.5 above 0.1 GeV is estimated to be 0.4-2.4 x 10(-6) ph cm(-2) s(-1) sr(-1) (4%-23% of the intensity of the isotropic diffuse component measured with the LAT). We anticipate that similar to 10 galaxies could be detected by their cosmic-ray-induced gamma-ray emission during a 10 year Fermi mission.
Keywords
cosmic rays, galaxies: starburst, gamma rays: diffuse background, gamma rays: galaxies
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-162396 (URN)10.1088/0004-637X/755/2/164 (DOI)000307791400081 ()2-s2.0-84864652181 (Scopus ID)
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2022-09-30Bibliographically approved
Ackermann, M., Ajello, M., Allafort, A., Atwood, W. B., Baldini, L., Barbiellini, G., . . . Zimmer, S. (2012). Measurement of Separate Cosmic-Ray Electron and Positron Spectra with the Fermi Large Area Telescope. Physical Review Letters, 108(1), Article ID 011103.
Open this publication in new window or tab >>Measurement of Separate Cosmic-Ray Electron and Positron Spectra with the Fermi Large Area Telescope
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2012 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, no 1, article id 011103Article in journal (Refereed) Published
Abstract [en]

We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting Earth's shadow, which is offset in opposite directions for opposite charges due to Earth's magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 and 200 GeV. We confirm that the fraction rises with energy in the 20-100 GeV range. The three new spectral points between 100 and 200 GeVare consistent with a fraction that is continuing to rise with energy.
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-162437 (URN)10.1103/PhysRevLett.108.011103 (DOI)000298928500005 ()22304252 (PubMedID)2-s2.0-84860117875 (Scopus ID)
Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2022-10-03Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6141-458x

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