Electronic Telegram No. 404
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
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V723 CASSIOPEIAE
     J.-U. Ness and S. Starrfield, Arizona State University; G. Schwarz
and K. Vanlandingham, West Chester University; R. M. Wagner, LBT
Observatory; J. Lyke, Keck Observatory; C. E. Woodward, University of
Minnesota; and D. K. Lynch, The Aerospace Corporation, report that SWIFT
XRT observations of V723 Cas (N Cas 1995; IAUC 6213, 6214, 6221) were
obtained on Jan. 31.27 UT.  V723 Cas was detected in x-rays and
exhibited a super-soft-source spectrum with a peak around 0.4 keV.
The best derived black-body fit is for a temperature of 340000 K
and N_H = 1.6 x 10**(21) cm**(-2).  The flux was 7.8 x 10**(-13)
erg/cm**2/s.  This nova is too bright in x-rays to have returned to
quiescence, and -- given that it has been 11 years since discovery --
V723 Cas sets the record for being in outburst longer than any nova
observed in x-rays.  The previous record holder was GQ Mus, which was
observed by ROSAT to be turning off in x-rays nine years after discovery
(Shanley et al. 1995, Ap.J. 438, L95).  This detection supports the
observations of coronal lines in the infrared (IAUC 7259) and
suggests that further study at other wavelengths is warranted.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2006 CBAT
2006 February 17                 (CBET 404)               Daniel W. E. Green