A remarkable low-mass X-ray binary within 0.1 parsecs of the Galactic center

M. P. Muno, J. R. Lu, F. K. Baganoff, W. N. Brandt, G. P. Garmire, A. M. Ghez, S. D. Hornstein, M. R. Morris

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59 Scopus citations


Recent X-ray and radio observations by Muno et al. and Bower et al. have identified a transient low-mass X-ray binary (LMXB) located only 0.1 pc in projection from the Galactic center, CXOGC J174540.0-290031. In this paper, we report the detailed analysis of X-ray and infrared observations of the transient and its surroundings. Chandra observations detect the source at a flux of FX = 2 × 10-12 ergs cm-2 s-1 (2-8 keV). After accounting for absorption both in the interstellar medium (ISM) and in material local to the source, the implied luminosity of the source is only LX = 4 × 1034 ergs s-1 (2-8 keV; D = 8 kpc). However, the diffuse X-ray emission near the source also brightened by a factor of 2. The enhanced diffuse X-ray emission lies on top of a known ridge of dust and ionized gas that is visible in infrared images. We interpret the X-ray emission as scattered flux from the outburst and determine that the peak luminosity of CXOGC J174540.0-290031 was LX ≳ 2 × 10 36 ergs s-1. We suggest that the relatively small observed flux results from the fact that the system is observed nearly edge-on, so that the accretion disk intercepts most of the flux emitted along our line of sight. We compare the inferred peak X-ray luminosity to that of the radio jet. The ratio of the X-ray to radio luminosities, LX/LR ≲ 104, is considerably smaller than in other known LMXBs (≳10 5). This is probably because the jets are radiating with unusually high efficiency at the point where they impact the surrounding ISM. This hypothesis is supported by a comparison with mid-infrared images of the surrounding dust. Finally, we find that the minimum power required to produce the jet, Ljet ∼ 1037 ergs s-1, is comparable to the inferred peak X-ray luminosity. This is the most direct evidence yet obtained that LMXBs accreting at low rates release about half of their energy as jets.

Original languageEnglish (US)
Pages (from-to)228-239
Number of pages12
JournalAstrophysical Journal
Issue number1 I
StatePublished - Nov 1 2005

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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