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Kerr, M.ORCID iD iconorcid.org/0000-0002-0893-4073
Publications (4 of 4) 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., 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/0000-0002-0893-4073

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