[vsnet-alert 7299] (Fwd) a new, fast X-ray transient

[Ryoko Ishioka <ishioka@kusastro.kyoto-u.ac.jp>]

Date: Wed, 17 Apr 2002 14:36:22 -0400 (EDT)
From: Ron Remillard <rr@space.mit.edu>
Subject: [vsnet-alert 0] a new, fast X-ray transient

XTE J1901+014: a new, fast X-ray transient

The RXTE All-Sky Monitor has discovered a fast X-ray transient that
was initially thought to be a gamma ray burst, reported on the GCN
network as GRB020406. The event began on 2002 April 6.76268, lasting
more than 2 min and less than 3.15 hr, with a peak flux of 0.9 Crab
(2-12 keV).  (see http://xte.mit.edu/xtej1901+104). The ASM data show
rapid evolution to a very hard spectrum during this outburst, but the
IPN instruments failed to detect the source above 15 keV (K. Hurley,
private communication). Furthermore, archival ASM data show a previous
outburst at the same position on 1997 June 21.215, which was longer
than 6 min and less than 8 hr, with a peak flux of 0.4 Crab. The
combined ASM observations yield a best position: R.A. = 19h01m36s,
Decl. = +1 26'.4 (equinox J2000.0; estimated 3' uncertainty in
R.A. and 2' uncertainty in Decl.).  The error box contains one very
faint, unidentified X-ray source from the Einstein Galactic Plane
Survey: 2E1859.1+0122 (J2000 R.A. = 19h01m40.2s, Decl. = +1 27' 13'';
error radius 48''; Hertz and Grindlay 1988, AJ, 96, 233). The time
scale for these eruptions are reminiscent of the microquasar and black
hole binary V4641 Sgr, so we strongly encourage optical and radio
observations of XTE J1901+014.

        R. A. Remillard (M.I.T.) and D. A. Smith (U. Michigan), for
the RXTE ASM Team at M.I.T. and NASA Goddard Space Flight Center.

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