X-ray catalog and classification of 4FGL-DR4 UGSs Virtual Observatory Resource

Authors
  1. Neumann K.D.
  2. Falcone A.D.
  3. Dikerby S.
  4. Deppe S.
  5. Ferrara E.C.,Kennea J.A.
  6. Cenko B.
  7. Grove E.
  8. Published by
    CDS
Abstract

Our survey of the fourth Fermi Large Area Telescope catalog (4FGL) unassociated gamma-ray source regions using the X-Ray Telescope (XRT) and Ultraviolet/Optical Telescope (UVOT) on board the Neil Gehrels Swift Observatory (Swift) provides new XRT and UVOT source detections and localizations to help identify potential low-energy counterparts to unassociated Fermi gamma-ray sources. We present a catalog of 218 singlet and 70 multiplet Swift X-ray sources detected within the positional uncertainty ellipses of 244 unassociated Fermi gamma-ray sources from the 4FGL-DR4 catalog, 144 of which are not previously cataloged by S. Kerby et al (2021ApJ...923...75K, Cat. J/ApJ/923/75). For each X-ray source, we derive its X-ray flux and photon index, then use simultaneous UVOT observations with optical survey data to estimate its V-band magnitude. We use these parameters as inputs for a multilayer perceptron neural network classifier (NNC) trained to classify sources as blazars, pulsars, or ambiguous gamma-ray sources. For the 213 singlet sources with X-ray and optical data, we classify 173 as likely blazars (P_bzr_>0.99) and six as likely pulsars (P_bzr_<0.01), with 34 sources yielding ambiguous results. Including 70 multiplet X-ray sources, we increase the number of P_bzr_>0.99 sources to 227 and P_bzr_<0.01 sources to 16. For the subset of these classifications that have been previously studied, a large majority agree with prior classifications, supporting the validity of using this NNC to classify the unknown and newly detected gamma-ray sources.

Keywords
  1. gamma-ray-astronomy
  2. x-ray-sources
  3. visible-astronomy
  4. broad-band-photometry
  5. active-galactic-nuclei
  6. bl-lacertae-objects
  7. pulsars
Bibliographic source Bibcode
2026ApJ...999..244N
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/999/244
IVOA Identifier IVOID
ivo://CDS.VizieR/J/ApJ/999/244

Access

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https://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/999/244
https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/999/244
http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/999/244
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https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/999/244/table9a?
https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/999/244/table9a?
http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/999/244/table9a?
IVOA Cone Search SCS
For use with a cone search client (e.g., TOPCAT).
https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/999/244/table9b?
https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/999/244/table9b?
http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/999/244/table9b?

History

2026-06-11T13:44:12Z
Resource record created
2026-06-11T13:44:12Z
Created
2026-06-12T13:45:41Z
Updated

Contact

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CDS support team
Postal Address
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