A variability analysis of low-latitude unidentified gamma-ray sources
Abstract
We present a study of 40 low-latitude unidentified 3EG gamma-ray sources which were found to be not positionally coincident with any known class of potential gamma-ray emitters in the Galaxy (Romero et al. 1999). We have performed a variability analysis which reveals that many of these 40 sources are variable. These sources have, in addition, a steep mean value of the gamma-ray spectral index, <Gamma > = 2.41 +/- 0.2, which, combined with the high level of variability, seems to rule out a pulsar origin. The positional coincidences with uncatalogued candidates to supernova remnants were also studied. Only 7 sources in the sample are spatially coincident with these candidates, a result that is shown to be consistent with the expected level of pure chance association. A complementary search for weak radio counterparts was also conducted and the results are presented as an extensive table containing all significant point-like radio sources within the 40 EGRET fields. We argue that in order to produce the high variability, steep gamma-ray spectra, and absence of strong radio counterparts observed in some of the gamma-ray sources of our sample, a new class of objects should be postulated, and we analyze a viable candidate. Tables 5--8 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5}) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/370/468}
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 2001
- DOI:
- 10.1051/0004-6361:20010239
- arXiv:
- arXiv:astro-ph/0007464
- Bibcode:
- 2001A&A...370..468T
- Keywords:
-
- Astrophysics;
- General Relativity and Quantum Cosmology
- E-Print:
- Paper updated to match the accepted version to appear in Astronomy and Astrophysics, 2001. Tables 5,6,7 and 8 are in ascii format and need to be printed separately. they can also be obtained from http://www.iar.unlp.edu.ar/garra Table 5 is 62 pages long. Download the source to obtain the tables