Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data

Baldini L, Ballet J, Bastieri D, Becerra Gonzalez J, Bellazzini R, Berretta A, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bottacini E, Bruel P, Buson S, Cameron RA, Caraveo PA, Cavazzuti E, Chen S, Chiaro G, Ciangottini D, Cibario N, Ciprini S, Cristarella Orestano P, Crnogorcevic M, Cutini S, D'Ammando F, De La Torre Luque P, De Palma F, Digel SW, Di Lalla N, Dirirsa F, Di Venere L, Dominguez A, Fiori A, Fleischhack H, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Germani S, Giglietto N, Giordano F, Giroletti M, Green D, Grenier IA, Griffin S, Guiriec S, Gustafsson M, Hewitt JW, Horan D, Imazawa R, Johannesson G, Kerr M, Kocevski D, Kuss M, Larsson S, Latronico L, Li J, Liodakis I, Longo F, Loparco F, Lovellette MN, Lubrano P, Maldera S, Manfreda A, Martí-Devesa G, Matake H, Mazziotta MN, Mereu I, Meyer M, Mirabal N, Mitthumsiri W, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Nagasawa S, Negro M, Ojha R, Orienti M, Orlando E, Palatiello M, Paliya V, Paneque D, Pei Z, Persic M, Pesce-Rollins M, Petrosian V, Poon H, Porter TA, Principe G, Racusin JL, Raino S, Rando R, Rani B, Razzano M, Razzaque S, Reimer A, Reimer O, Saz Parkinson PM, Scotton L, Serini D, Sgro C, Siskind EJ, Spandre G, Spinelli P, Suson DJ, Tajima H, Tak D, Torres DF, Tosti G, Troja E, Wood K, Yassine M, Zaharijas G (2021)

Publication Type: Journal article

Publication year: 2021


Book Volume: 256

Journal Issue: 1

DOI: 10.3847/1538-4365/ac072a


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.

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Involved external institutions

University of Pisa / Università di Pisa (UniPi) IT Italy (IT) University of Paris 4 - Paris-Sorbonne / Université paris IV Paris-Sorbonne FR France (FR) National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN) IT Italy (IT) Instituto de Astrofísica de Canarias (IAC) ES Spain (ES) Università degli Studi di Perugia IT Italy (IT) University of Bari Aldo Moro / Università degli Studi di Bari Aldo Moro IT Italy (IT) Stanford University US United States (USA) (US) École Polytechnique - Université Paris-Saclay FR France (FR) Julius-Maximilians-Universität Würzburg DE Germany (DE) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) IT Italy (IT) Italian Space Agency / Agenzia Spaziale Italiana (ASI) IT Italy (IT) Università del Salento IT Italy (IT) University of Savoy Mont Blanc / Université Savoie Mont Blanc FR France (FR) Catholic University of America US United States (USA) (US) Ruhr-Universität Bochum (RUB) DE Germany (DE) Hiroshima University / 広島大学 JP Japan (JP) Max-Planck-Institut für Physik (Werner-Heisenberg-Institut, MPP) / Max Planck Institute for Physics DE Germany (DE) National Aeronautics and Space Administration (NASA) US United States (USA) (US) Georg-August-Universität Göttingen DE Germany (DE) University of North Florida (UNF) US United States (USA) (US) University of Iceland (UI) / Háskóli Íslands IS Iceland (IS) U.S. Naval Research Laboratory US United States (USA) (US) Royal Institute of Technology / Kungliga Tekniska Högskolan (KTH) SE Sweden (SE) Deutsches Elektronen-Synchrotron DESY DE Germany (DE) University of Maryland US United States (USA) (US) Universidad Complutense de Madrid (UCM) ES Spain (ES) University of California Santa Cruz US United States (USA) (US) University of Turku / Turun yliopisto FI Finland (FI) Leopold-Franzens-Universität Innsbruck / University of Innsbruck AT Austria (AT) George Washington University (GWU) US United States (USA) (US) Mahidol University / มหาวิทยาลัยมหิดล TH Thailand (TH) University of Tokyo JP Japan (JP) University of Padua / Universita degli Studi di Padova IT Italy (IT) University of Johannesburg ZA South Africa (ZA) University of Montpellier / Université Montpellier FR France (FR) NYCB Real-Time Computing, Inc. US United States (USA) (US) Purdue University Northwest / Purdue University Calumet US United States (USA) (US) Spanish National Research Council / Consejo Superior de Investigaciones Científicas (CSIC) ES Spain (ES) Praxis, Inc. US United States (USA) (US)

How to cite


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).


Baldini, Luca, et al. "Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data." Astrophysical Journal Supplement Series 256.1 (2021).

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