Volume 370, Number 2, May I 2001
|Page(s)||468 - 478|
|Section||Interstellar and circumstellar matter|
|Published online||15 May 2001|
A variability analysis of low-latitude unidentified gamma-ray sources*
Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Buenos Aires, Argentina
2 Depto. de Astronomía, Univ. Guanajuato, Apartado Postal 144, Guanajuato, CP 36000, GTO, Mexico
3 4014 Emerald Street No. 116, Torrance, CA 90503, USA
Corresponding author: D. F. Torres, firstname.lastname@example.org
Accepted: 26 January 2001
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, , 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.
Key words: gamma-rays: observations / gamma-rays: theory / ISM: supernova remnants / black holes physics
© ESO, 2001
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