[vsolj-alert 772] XTE J1118+480 ASCA result

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

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From: ueda@astro.isas.ac.jp
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Subject: [vsnet-campaign 100] XTE J1118+480 ASCA results
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Hi, 

  We have just submitted the following to the IAUC about ASCA
observation of XTE J1118+480.

Best regards,
Yoshihiro Ueda
ISAS

------------
XTE J1118+480

K. Yamaoka, Y. Ueda, and T. Dotani, The Institute of Space and
Astronautical Science, and Ph. Durouchoux and J. Rodriguez, CE
Saclay, Service d'Astrophysique report:

We observed the X-ray transient XTE J1118+480 with the ASCA satellite
from 2000 May 11 12:40 to May 12 0:45 (UT). The X-ray intensity showed
rapid variability over an averaged flux level of 8E-10 erg cmE-2 sE-1
(2-10 keV). A QPO feature was found at 0.115 +/- 0.002 (Hz) with an
amplitude of about 6% rms in the averaged power spectrum. The presence
of the 0.11 Hz QPO was confirmed by simultaneous RXTE data, which
covered two epochs from May 11 17:30 to 17:57 and from 18:45 to 22:21. 
The QPO frequency shifted from the previous value before May 4 (0.085
+/- 0.002 Hz) reported by Revnivtsev et al (astro-ph/0005212).  The
ASCA GIS spectrum in the 0.7-10 keV range is approximately
represented by a power law, over which a slight soft excess is seen
below 2 keV. Applying a disk blackbody and power law model yields an
acceptable fit with a temperature of the innermost disk of 0.2 +/- 0.1
keV, a power law photon index of 1.76 +/- 0.02, with an upper limit to
an absorption column density of 1E21 cmE-2.

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