New X-ray Transient, XTE J1818-254
ATel #578; 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
on 16 Aug 2005; 05:11 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Ron Remillard (rr@space.mit.edu)
Subjects: X-ray, Transient
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.
