A search for new sources below 100 MeV in the Fermi-LAT data

Abstract

The Fermi Large Area Telescope (LAT) has discovered more than 3000 sources between 100 MeV and 300 GeV (3FGL), including over 200 \(\gamma \)-ray pulsars. The majority of these pulsars have their spectral energy peaks (in \(\nu F_{\nu }\)) above 1 GeV. There exists another population of very energetic, young rotation-powered pulsars having non-thermal hard X-ray emission with spectral energy distributions (SEDs) peaking around 1 MeV, but having no detected emission by Fermi LAT above 100 MeV. Previous analyses of point sources in the gamma ray range were done only below 30 MeV (COMPTEL) or above 100 MeV (Fermi-LAT). Below 30 MeV, the imaging Compton telescope (COMPTEL) detected 26 steady sources in the energy range from 0.75 to 30 MeV. Since the Fermi LAT detects gamma rays down to 20 MeV, we create a list of sources detected in the energy range between 30 MeV and 100 MeV, using PGWave, a background-independent tool that makes use of a wavelet transform. This closes a gap of point source analysis between the COMPTEL catalog and the Fermi-LAT catalog and provides information and constraint for this missing MeV pulsar population.

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Notes

  1. 1.

    At energies below 100 MeV, the uncertainties in the photon arrival direction are very large. A measure of the quality of the direction reconstruction is used to assign events to four quartiles.

  2. 2.

    https://fermi.gsfc.nasa.gov/ssc/data/access/lat/fl8y/.

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Acknowledgements

The Fermi-LAT Collaboration acknowledges support for LAT development, operation and data analysis from NASA and DOE (USA), CEA/Irfu and IN2P3/CNRS (France), ASI and INFN (Italy), MEXT, KEK, and JAXA (Japan), and the K.A. Wallenberg Foundation, the Swedish Research Council and the National Space Board (Sweden). Science analysis support in the operations phase from INAF (Italy) and CNES (France) is also gratefully acknowledged.

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Correspondence to G. Principe.

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This paper is the peer-reviewed version of a contribution selected among those presented at the Conference on Gamma-Ray Astrophysics with the AGILE Satellite held at Accademia Nazionale dei Lincei and Agenzia Spaziale Italiana, Rome on December 11–13, 2017.

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Principe, G., Malyshev, D., Ballet, J. et al. A search for new sources below 100 MeV in the Fermi-LAT data. Rend. Fis. Acc. Lincei 30, 255–258 (2019). https://doi.org/10.1007/s12210-019-00771-2

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Keywords

  • Gamma rays: general-catalog
  • Pulsars