1999/04/28 by L. Sidoli, S. Mereghetti, G. L. Israel +3 · 6 citations
Engineering · Physics and Astronomy · #Astrophysical Phenomena and Observations #Mechanics and Biomechanics Studies #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1086/307887
published as Astrophys.J. 525 (1999) 215 · 34 pages, 11 figures and 3 tables included, accepted for publication in ApJ
arxiv created 1999/04/28 · openalex publication_date 1999/11/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We report the results of a survey of the Galactic center region (∣ l ∣ < 2°, ∣ b ∣ < 0 5) performed with the BeppoSAX satellite. The flux from the center of our Galaxy corresponds to a luminosity of ~3 × 10 35 ergs s -1 in the 2-10 keV range. Due to the limited angular resolution (≳1'), only part of it is supposed to come from Sagittarius A*, the nonthermal radio source that is believed to mark the dynamical center of the Galaxy. In addition to the diffuse emission, several bright ( L X ≳ 10 36 ergs s -1 ) point sources have been observed, both persistent (A1742-294, SLX 1744-299, SLX 1744-300, 1E 1743.1-2843, 1E 1740.7-2942) and transient (XTE J1748-288, SAX J1747.0-2853 and KS 1741-293). The low-mass X-ray binary (LMXRB) AX J1745.6-2901, discovered with ASCA at only 1 3 from Sgr A*, was detected in a low-luminosity state in 1997 August. The 1-150 keV spectrum of the hard X-ray source 1E 1740.7-2942 is well described by a Comptonization model, typical of black hole candidates in their low/hard state, with no evidence for strong Fe lines. The detection of a type I burst shows that the transient source SAX J1747.0-2853 (probably the same as the 1976 transient GX 0.2-0.2) is a LMXRB containing a neutron star. The transient black hole candidate XTE J1748-288 was detected at a luminosity (~10 36 ergs s -1 ) consistent with the extrapolation of the exponential decay of the outburst observed with the XTE All-Sky Monitor. Two fainter sources are very likely associated with young neutron stars: the (possibly diffuse) X-ray source at the center of the composite supernova remnant G0.9+0.1, and the "head" of the axially symmetric radio source G359.23-0.92. The latter has been detected above ~6 keV, supporting a nonthermal emission mechanism.