[vsnet-alert 4501] (fwd) XTE J1118+480

[Taichi Kato <tkato>]

(fwd) XTE J1118+480

Date: Thu, 30 Mar 2000 11:21:41 -0500 (EST)
From: Ron Remillard <rr@space.mit.edu>

The RXTE All-Sky Monitor has detected X-ray emission from a new
source, XTE J1118+480. The ASM position (equinox 2000.0, with a 90%
confidence radius of 6') is centered at R.A. = 11h 18m 17s, 
Decl. = +48o 03'.0 The average X-ray intensity (2-12 keV) is 
39(8) mCrab on March 29. Retrospective ASM analysis indicates that the 
X-ray flux has been slowly rising since March 5. Another modest outburst
had pviously occurred during Jan 29 2000, peaking at 37(3) mCrab on
Jan 6. The SIMBAD database lists only an unremarkable guide star (V~11)
near the X-ray position. The source was confirmed in an 800 s 
RXTE pointed observation beginning on 23:14 UT March 29. Rapid flares 
(e.g. 10 s) were seen, reaching a factor of 5 above the baseline flux 
near 25 mCrab and suggesting a Galactic X-ray source. No pulsations 
were deteed. The X-ray spectrudoes not vary appciably during 
intense flares. Preliminary spectral analysis indicates a power-law
visible to 30 keV. The photon index is roughly 1.8, which is similar
to Cyg X-1 in its hard state. The high galactic latitude (62o) 
and X-ray properties present a puzzling combination, 
and observations at other wavelengths are urgently needed.

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