[Wu, Y. X.
; Yu, W.] Shanghai Astron Observ, Shanghai 200030, CA, Peoples R China
; [Wu, Y. X.
; Li, T. P.] Tsinghua Univ, Ctr Astrophys, Beijing 100084, Peoples R China
; [Wu, Y. X.
; Li, T. P.] Tsinghua Univ, Dept Engn Phys, Beijing 100084, Peoples R China
; [Li, T. P.] Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China
; [Li, T. P.] Chinese Acad Sci, Inst High Energy Phys, Particle Astrophys Lab, Beijing, Peoples R China
; [Maccarone, T. J.] Univ Southampton, Sch Phys & Astron, Southampton SO17 1BJ, Hants, England
; [Li, X. D.] Nanjing Univ, Dept Astron, Nanjing 210093, Peoples R China
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.