[IAUC] CBET 718: 20061103 : BRIGHT VARIABLE STAR IN CASSIOPEIA

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                                                  Electronic Telegram No. 718
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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BRIGHT VARIABLE STAR IN CASSIOPEIA
     U. Munari, A. Siviero, L. Tomasella, and M. Valentini, Istituto
Nazionale di Astrofisica, Astronomical Observatory of Padova, write that a
series of echelle spectra (range 380-730 nm, resolving power 20000) have
been secured of the new bright variable star in Cas (cf. CBETs 711, 712)
with the Asiago 1.82-m telescope on Nov. 1.85, 2.73, and 3.71 UT.  The
spectra are characterized by a hot continuum with Balmer and Mg II 448.1-nm
absorption lines whose heliocentric radial velocities on the three nights
are -36, -34, and -34 (+/- 1) km/s, respectively.  The broad wings of the
Balmer lines indicate a surface gravity similar to that of main sequence
dwarfs.  No helium lines are visible, and Balmer absorption lines do not
present an emission core.  The absorption line cores are sharp enough to
exclude a fast rotation.  The strong insterstellar Na I D doublet is visible
at heliocentric radial velocity -14 (+/- 1) km/s.  The mean 0.049-nm
equivalent width of the Na I D2 589.0-nm line corresponds to a reddening
E(B-V) = 0.29, following calibration via Munari and Zwitter (1997, A.Ap.
318, 269).  The object's brightness has been noted to decrease markedly from
one night to the next.  In comparison with the spectra from Nov. 1.85, the
Balmer and Mg II 448.1-nm aborption lines have increased their equivalent
widths by 30 percent on Nov. 2.73 and by 55 percent on Nov. 3.71.  On the
Nov. 3.71 spectrum, H_beta reaches a 1.25-nm equivalent width, which is
appropriate for an early A-type main-sequence star.  Inspection of the
stellar seeing disk (2".2) on the TV screen of the telescope guiding system
does not reveal the presence of a close bright companion.
     T. Iijima, Astronomical Observatory of Padova, reports that spectra
(range 360-740 nm), of variable star report on CBET 711 were taken with a
Boller & Chivens grating spectrograph mounted on the 1.22-m telescope of the
Asiago Astrophysical Observatory on Nov. 2.08 and 2.12 UT.  The spectra show
an extremely blue continuum superimposed by clear absorptions of the H I
Balmer series.  Also, H-alpha is in pure absorption.  The absorption lines
of Ca II H and K and Na I D are seen; meanwhile, no He I line is seen in
absorption nor in emission.  The continuum is still bluer than that of the
O5-type star HD 217086, but the absorption features resemble an A-type star.
This object may be a type of dwarf novae in outburst.
     R. Tucker, Tucson, AZ, reports the following astrometry of this
variable star from several CCD images:  R.A. = 0h09m21s.98 +/- 0s.02, Decl.
= +54d39'45".6 +/- 1".6 (equinox 2000.0).  Tucker provides the following V
magnitudes for the variable:  Nov. 1.148 UT, 9.2; 1.188, 9.3; 2.089, 9.3.  A
star of red mag 12.0 is visible on a Digitized Sky Survey U.K. Schmidt plate
from Sept. 19.319, and he measures position end figures for that star:
21s.97, 44".0.  (There is also a nearby star of red mag 11.9-12.0 located at
position end figures 24s.66 +/- 0s.02, 40'08".4.)  Tucker adds that his
spectra taken with a 0.36-m Schmidt-Cassegrain telescope (+ SBIG SGS
spectrograph; range 421.9-750.4 nm; disperson 0.43 nm/pixel) shows hydrogen
absorption lines fading in intensity between Nov. 1.17 and 2.12; the
spectrum appears very similar to that of a star of spectral class A7 except
for a weak emission feature at 466.7 nm.
     S. Nakano, Sumoto, Japan, forwards the following position end figures
for the variable star from K. Itagaki (Teppo-cho, Yamagata, Japan; 0.60-m
f/5.7 reflector), who reported unfiltered mag 9.4 from his image taken on
Nov. 1.431 UT (which was fainter than on the previous night):  21s.98,
43".9.
     N. N. Samus, Institute of Astronomy, Russian Academy of Sciences,
writes that S. V. Antipin (Sternberg Institute) has searched 405 plates of
the Moscow archive spanning 1964 July 12-1994 Oct. 7; the star that now
appears to be varying in brightness appears constant at photographic
magnitude 11.8 +/- 0.1 (using Tycho B magnitudes for comparison stars).  If
variable, this star never was outside the magnitude range 11.7-12.0 on these
archival plates.
     G. M. Hurst, Basingstoke, Hants, England, reports that M. Collins
(Everton, Bedfordshire, England) has derived the following magnitudes from
his images secured for the U.K. Nova/Supernova Patrol using a Canon 10D
camera and 85-mm-focal-length f/1.8 lens (30-s twin exposures for each
date):  2006 Sept. 22.925 UT, 11.7; Oct. 21.863, 10.9.
     Visual magnitude estimates:  Oct. 31.89 UT, 8.5 (M. Reszelski,
Szamotuly-Galowo, Poland); 31.910, 8.6 (R. J. Bouma, Groningen, The
Netherlands); 31.919, 8.6 (P. Schmeer, Bischmisheim, Germany); 31.984, 8.7
(Hurst); Nov. 1.753, 9.4 (Schmeer); 1.759, 9.5 (Bouma); 1.844, 9.3 (A.
Diepvens, Balen, Belgium); 2.740, 10.1 (Diepvens); 2.84, 9.6 (Reszelski);
3.94, 10.5 (Reszelski).


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

                         (C) Copyright 2006 CBAT
2006 November 3                  (CBET 718)               Daniel W. E. Green