ATel #143; C. B. Markwardt (U. Maryland & GSFC)
on 9 Apr 2003; 03:09 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Craig B. Markwardt (email@example.com)
Subjects: X-ray, Request for Observations, Binary, Black Hole, Transient
C. B. Markwardt (U. Maryland & NASA/GSFC) reports the detection of a
source in the galactic center region with RXTE PCA bulge monitoring
scans, whose position is consistent with that of SLX 1746-331 (Skinner
et al. 1990, MNRAS, 243, 72). This position is quite distinct from
that of the recently-active IGR J17464-3213 (= XTE J1746-322 =
H1743-322), which lies 1.2 degrees to the north. Previous transient
outbursts of SLX 1746-331 have been seen in 1985 and 1990.
Both Skinner et al. (1990) and White and van Paradijs (1996, ApJL,
473, L25) speculate that SLX 1746-331 contains a black hole, based on
its transient nature and its soft spectrum (optically thick, kT ~ 1
keV). Indeed, a pointed observation of the source on Apr 7.99 (UT)
with the PCA detected a very soft spectrum, consistent with "disk"
black body emission (kT_BB = 1.3 keV).
Motch et al (1998, A&AS, 132, 341) identify the source from the ROSAT
All-Sky Survey as RX J1749.8-3312 = 1RXS J174948.4-331215, whose
coordinates are R.A. = 17h49m50.6s, Decl. = -33d11m55s (equinox
Approximate 2-10 keV X-ray fluxes were: Apr 5.65, 40 mCrab; Apr 7.99,
160 mCrab; Apr 8.65, 210 mCrab. As the flux is rapidly rising,
observations at other wavelengths are desireable. I am requesting
further observations with RXTE.