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SLX 1746-331

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 (craigm@lheamail.gsfc.nasa.gov)

Subjects: X-ray, Request for Observations, Binary, Black Hole, Transient

Referred to by ATel #: 144, 145, 169, 1235, 1633

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 2000.0).

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.