[vsnet-alert 8614] (fwd) New X-ray Transient, XTE J1818-254 (ATEL)

[Taichi Kato]

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The Astronomer's Telegram                   http://www.astronomerstelegram.org 
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ATEL #578                                                            ATEL #578

Title:          New X-ray Transient, XTE J1818-254
Author:         A. M. Levine (MIT), J. H. Swank (GSFC), D. Lin (MIT), and
                R. A. Remillard (MIT), for the ASM team at MIT and NASA/GSFC
Queries:        rr at space.mit.edu
Posted:         16 Aug 2005;  5:11  UT
Subjects:       X-ray, Transients

Observations with the RXTE All-Sky Monitor reveal X-ray emission from
a new transient at coordinates 274.60, -24.53 (degrees, J2000),   with
a position uncertainty of 0.10 degrees at 90% confidence.   The source
was first detected on 2005 August 12, with an average flux   of 55 (5)
mCrab at 2-12 keV.  By 2005 August 14 the flux had increased   to 510 (9),
with a similar flux of 470 (13) mCrab on August 15.   The ASM hardness
ratio (5-12 keV to 3-5 keV) indicates a very   soft spectrum, suggesting
a black-hole binary with a thermal-type spectrum.     Observations at other
wavelengths are needed as soon as possible.