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[vsolj-alert 644] XTE J1118+480 spectroscopy




 さらに以下の情報が入っています。もし軌道傾斜が高ければ食が観測できるかも
 知れません。等級も明るいため、可視光でも頻度の高いモニターが望まれます。
 もし食らしい変動が観測された場合、緊急通報が望まれます。

Date: Fri, 31 Mar 2000 22:28:31 -0500 (EST)
From: Mike Garcia <garcia@head-cfa.harvard.edu>
Subject: [vsnet-alert 4527] Optical Spectroscopy and Photometry of XTE J1118+480
Dear Colleagues:

	We have submitted the following to the IAUC:


M. Garcia, W. Brown, M. Pahre, J. McClintock (Harvard/Smithsonian
Center for Astrophysics, P. Callanan (University College, Cork), and
P. Garnavich (Notre Dame) report:

Optical spectroscopy of XTE J1118+38 on the night of March 31 (UT)
reveals a spectrum typical of an x-ray nova in outburst (ie, Shafer et
al 1994 ApJ 434, 698).  A series of spectra obtained with the FLWO
1.5m telescope and FAST spectrograph show H-alpha, H-beta, and HeII
468.6 nm emission with equivalent widths (nm) and FWHM (km/sec),
accurate to 10%, of 0.19, 2200; 0.01, --; 0.12, 2690, respectively.
The H-alpha FWHM we find in this x-ray nova is approximately equal to
the largest seen in quiescent black-hole x-ray novae.  The H-alpha
line shows two blue-ward absorption features, and the H-beta line
shows red-ward and blue-ward absorption features.  The NaD 589.0 nm
line has an equivalent width of 0.004 nm, indicating very low
interstellar absorption.  The column density out of the plane in this
direction (Dickey & Lockman, 1990, ARAA. 28, p215) corresponds to an
E(B-V)~0.024.  Differential V-band photometry from the FLWO 1.2m
telescope, relative to USNO A2.0 1350_08091237 with V=10.91, finds
magnitudes of 12.80(0.1) and 13.05(0.1) on March 31.151 and 31.396,
respectively. The surprisingly low x-ray to optical flux ratio (ie,
V~13, Fx~40 mCrab, IAUC 7389) may be due to a nearly edge-on viewing
angle.

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