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Title: Search for gamma-ray emission from Galactic novae with the Fermi-LAT

Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically detected Galactic novae in the first 7.4 years of operation of the Fermi Large Area Telescope using the Pass 8 data set. Aims. We compile an optical nova catalog including light curves from various resources and estimate the optical peak time and optical peak magnitude in order to search for gamma-ray emission to determine whether all novae are gamma-ray emitters. Methods. We repeated the analysis of the six novae previously identified as gamma-ray sources and developed a unified analysis strategy that we then applied to all novae in our catalog. We searched for emission in a 15 day time window in two-day steps ranging from 20 days before to 20 days after the optical peak time. We performed a population study with Monte Carlo simulations to set constraints on the properties of the gamma-ray emission of novae. Results. Two new novae candidates have been found at ~ 2σ global significance. Although these two novae candidates were not detected at a significant level individually, takingmore » them together with the other non-detected novae, we found a sub-threshold nova population with a cumulative 3σ significance. We report the measured gamma-ray flux for detected sources and flux upper limits for novae without significant detection. Lastly, our results can be reproduced by several gamma-ray emissivity models (e.g., a power-law distribution with a slope of 2), while a constant emissivity model (i.e., assuming novae are standard candles) can be rejected.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
  2. Centre National de la Recherche Scientifique (CNRS), Toulouse (France). Inst. de Recherche en Astrophysique et Planetologie (IRAP); Univ. de Toulouse, Toulouse (France). Galaxies, Astrophysique des Hautes Energies et Cosmologie (GAHEC)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States). W. W. Hansen Experimental Physics Lab., Kavli Inst. for Particle Astrophysics and Cosmology, Dept. of Physics
  4. Naval Research Lab. (NRL), Washington, DC (United States). Space Science Division
  5. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Astronomy and Astrophysics
Additional Journal Information:
Journal Volume: 609; Journal ID: ISSN 0004-6361
EDP Sciences
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier: