Orbital period and outburst luminosity of transient low mass X-ray binaries

Y. X. Wu, W. Yu, T. P. Li, T. J. MacCarone, X. D. Li

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In this paper, we investigate the relationship between the maximal luminosity of X-ray outburst and the orbital period in transient low mass X-ray binaries (or soft X-ray transients) observed by the Rossi X-ray Timing Explorer (RXTE) in the past decade. We find that the maximal luminosity (3-200 keV) in Eddington units generally increases with increasing orbital period, which does not show a luminosity saturation but in general agrees with theoretical prediction. The peak luminosities in ultra-compact binaries might be higher than those with an orbital period of 2-4 hr, but more data are needed to make this claim. We also find that there is no significant difference in the 3-200 keV peak outburst luminosity between neutron star (NS) systems and black hole (BH) systems with orbital periods above 4 hr; however, there might be a significant difference at smaller orbital periods where only NS systems are observed and radiatively inefficient accretion flow is expected to work at low luminosities for BH accreters.

Original languageEnglish
Pages (from-to)620-631
Number of pages12
JournalAstrophysical Journal
Issue number2
StatePublished - Aug 1 2010


  • Accretion, accretion disks
  • Binaries: close
  • X-rays: binaries


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