The X-ray Binary GRS 1741.9-2853 in Outburst and Quiescence

Abstract

We report Chandra and XMM-Newton observations of the transient neutron star low-mass X-ray binary GRS 1741.9-2853. Chandra detected the source in outburst on 2000 October 26 at an X-ray luminosity of ~10^{36} erg/s (2--8 keV; 8 kpc), and in quiescence on 2001 July 18 at ~10^{32} erg/s. The latter observation is the first detection of GRS 1741.9-2853 in quiescence. We obtain an accurate position for the source of 17h 45m 2.33s, -28o 54' 49.7" (J2000), with an uncertainty of 0.7". GRS 1741.9-2853 was not detected significantly in three other Chandra observations, nor in three XMM-Newton observations, indicating that the luminosity of the source in quiescence varies by at least a factor of 5 between (< 0.9 - 5.0) \times 10^{32} erg/s (2--8 keV). A weak X-ray burst with a peak luminosity of 5 \times 10^{36} erg/s above the persistent level was observed with Chandra during the outburst on 2000 October 26. The energy of this burst, 10^{38} erg, is unexpectedly low, and may suggest that the accreted material is confined to the polar caps of the neutron star. A search of the literature reveals that GRS 1741.9-2853 was observed in outburst with ASCA in Fall 1996 as well, when the BeppoSAX WFC detected the three previous X-ray bursts from this source. The lack of X-ray bursts from GRS 1741.9-2853 at other epochs suggests that it produces bursts only during transient outbursts when the accretion rate onto the surface of the neutron star is about 10^{-10} M_sun/yr. A similar situation may hold for other low-luminosity bursters recently identified from WFC data.