[vsnet-alert 7616] (fwd) New X-ray Transient, XTE J1720-318

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Date: Tue, 14 Jan 2003 22:24:57 -0500 (EST)
From: Ron Remillard <rr@space.mit.edu>
Subject: New X-ray Transient, XTE J1720-318

New X-ray Transient, XTE J1720-318

R. A. Remillard, A. M. Levine, and E. H. Morgan (M.I.T.), and
E. Smith, and J. Swank (NASA GSFC), for the RXTE All Sky Monitor Team
at M.I.T. and NASA's Goddard Space Flight Center, report the discovery
of a transient X-ray source at R.A. = 17h19m58s, Decl. = -31 46'.8
(equinox J2000.0; estimated 3' uncertainty at 90% confidence).  The
source was first detected on 2003 January 9 when the average flux
(2-12 keV) was 130 +- 20 mCrab. The intensity increased to 430 +- 40
mCrab on Jan. 10 and 400 +- 20 mCrab on Jan. 13.  A brief observation
of the ASM position on January 14 with the RXTE PCA confirms the
presence of a bright transient.  More extensive observations with the
PCA and HEXTE, including raster scans to improve the source position,
are planned starting Jan. 15.  The error circle does not contain any
noteworthy sources in the Simbad catalogs.  The ASM hardness ratios
indicate that the spectrum was moderately hard Jan. 9-10 and
relatively soft on Jan. 13.  These results resemble the early spectral
evolution of X-ray transients known to contain an accreting black hole. 
We encourage optical and radio observations of this new transient.

-----

Ron Remillard
MIT

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