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IAUC 7889: XTE J0929-314; V838 Mon

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                                                  Circular No. 7889
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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XTE J0929-314
     J. G. Greenhill, A. B. Giles, and K. M. Hill, University of
Tasmania, report a possible optical counterpart for XTE J0929-314
(cf. IAUC 7888).  Observations obtained around May 1.42-1.58 UT at
the 1-m Mt. Canopus telescope show a blue object with V about 18.8
at R.A. = 9h29m20s.16, Decl. = -31o23'02".7 (equinox J2000.0;
uncertainty +/- 0".5).  The object was also detected in B, R, and
I, but not on a red plate from the Digitized Sky Survey.  The
source faded significantly during the observations.

     A. Henden, Universities Space Research Association and U.S.
Naval Observatory (USNO); U. Munari, P. Marrese, and F. Boschi,
Osservatorio Astrofisico di Asiago; and R. Corradi, Isaac Newton
Group of Telescopes, La Palma, report that the light echo
surrounding V838 Mon is now developing an inner edge on U-band
images obtained with the USNO 1-m telescope, about 6" radius from
the star on Apr. 30.2 UT and propogating outwards.  This is caused
by the large and fast drop in U-band brightness at 0.17 mag/day
that V838 Mon has experienced over the last few days:  Apr. 18.12,
U = 14.09; 22.14, 14.76; 30.13, 16.09.  Continuing the trend, the
light echo should disappear by late May, when the fading front will
have reached the outer 34" radius that has held firm for the past
month.  High-resolution echelle CCD spectra obtained with the
Asiago 1.82-m telescope on Apr. 22.81 show the development of M-
giant absorption features.  Narrow P-Cyg profiles still persist for
several metallic lines and Na I D, while the Ca II near-infrared
triplet is now in pure absorption.  The only significant emission
feature is H-alpha with a multipeaked complex profile of 220 km/s
half-width and -5.5 km/s heliocentric radial velocity for the
strongest peak.  Remarkable TiO bands in absorption resemble an
M6/7 spectrum.  No carbon-related absorption bands are evident.
     Visual magnitude estimates:  Mar. 5.79 UT, 7.4 (K. Sarneczky,
Piszkesteto, Hungary); 8.441, 7.0 (S. Yoshida, Ibaraki, Japan);
11.860, 7.7 (M. Martignoni, Busto Arsizio, Italy); 15.82, 7.4 (A.
R. Baransky, Kiev, Ukraine); 19.067, 7.5 (R. Y. Shida, Sao Paulo,
Brazil); 26.793, 8.0 (K. Hornoch, Lelekovice, Czech Republic); Apr.
2.800, 8.2 (Hornoch); 4.950, 8.0 (Shida); 10.038, 8.4 (Shida);
12.034, 8.7 (Shida); 15.968, 9.0 (Shida).

                      (C) Copyright 2002 CBAT
2002 May 1                     (7889)            Daniel W. E. Green

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