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Bastieri, D.ORCID iD iconorcid.org/0000-0002-6954-8862
Publications (9 of 9) 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
Abdollahi, S., Acero, F., Ackermann, M., Ajello, M., Atwood, W. B., Axelsson, M., . . . Zaharijas, G. (2020). Fermi Large Area Telescope Fourth Source Catalog. Astrophysical Journal Supplement Series, 247(1), Article ID 33.
Open this publication in new window or tab >>Fermi Large Area Telescope Fourth Source Catalog
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2020 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 247, no 1, article id 33Article in journal (Refereed) Published
Abstract [en]

We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.
Keywords
Catalogs, Gamma-ray astronomy, Sky surveys
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-181064 (URN)10.3847/1538-4365/ab6bcb (DOI)000520200200001 ()2-s2.0-85091172627 (Scopus ID)
Available from: 2020-05-01 Created: 2020-05-01 Last updated: 2022-11-08Bibliographically 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., 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
Ackermann, M., Ajello, M., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., . . . Stroh, M. (2012). MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008-2009 FLARING STATE. Astrophysical Journal, 751(2), Article ID 159.
Open this publication in new window or tab >>MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008-2009 FLARING STATE
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2012 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 751, no 2, article id 159Article in journal (Refereed) Published
Abstract [en]

The blazarAO 0235+164 (z=0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to gamma-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the gamma-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R-g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.
Keywords
BL Lacertae objects: individual (AO 0235+164), galaxies: active, galaxies: jets, gamma rays: galaxies, radiation mechanisms: non-thermal
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-162405 (URN)10.1088/0004-637X/751/2/159 (DOI)000304204600080 ()2-s2.0-84861396505 (Scopus ID)
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2022-10-03Bibliographically approved
Ackermann, M., Ajello, M., Ballet, J., Barbiellini, G., Bastieri, D., Belfiore, A., . . . Torres, M. A. (2012). Periodic Emission from the Gamma-Ray Binary 1FGL J1018.6-5856. Science, 335(6065), 189-193
Open this publication in new window or tab >>Periodic Emission from the Gamma-Ray Binary 1FGL J1018.6-5856
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2012 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 335, no 6065, p. 189-193Article in journal (Refereed) Published
Abstract [en]

Gamma-ray binaries are stellar systems containing a neutron star or black hole, with gamma-ray emission produced by an interaction between the components. These systems are rare, even though binary evolution models predict dozens in our Galaxy. A search for gamma-ray binaries with the Fermi Large Area Telescope (LAT) shows that 1FGL J1018.6-5856 exhibits intensity and spectral modulation with a 16.6-day period. We identified a variable x-ray counterpart, which shows a sharp maximum coinciding with maximum gamma-ray emission, as well as an O6V((f)) star optical counterpart and a radio counterpart that is also apparently modulated on the orbital period. 1FGL J1018.6-5856 is thus a gamma-ray binary, and its detection suggests the presence of other fainter binaries in the Galaxy.
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-162434 (URN)10.1126/science.1213974 (DOI)000299033100045 ()22246769 (PubMedID)2-s2.0-84862908430 (Scopus ID)
Available from: 2019-01-02 Created: 2019-01-02 Last updated: 2022-10-03Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6954-8862

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