[vsnet-newvar 1690] HD 932 is a Cepheid Variable of 10.3: day period

[jg@jgws.freeisp.co.uk]

Preliminary photometry by Tom Droege, consisting of 174 paired Johnson V
and Cousins I measures (available via http://data.tass-survey.org/ , the
"november" collection ) reveal

HD 932 (RA 00h13m43.4 , Dec +06 56' 18" ; 2000)

to be a Cepheid variable of around 10.2 to 10.3 days period, with
amplitude ranging from V 8.9 to 9.4.

The lightcurve appears on the whole symmetrical, although only the
descending branch is well sampled enough to be certain of there being no
marked 'humps' in that part.

The spectrum is catalogued as A5, and the Tycho derived B-V of +0.3
would seem to fit that, however the V-Ic measures mentioned here average
+0.35, slightly more consistent with what would be expected from an
earliest F type Cepheid.  Examination of the Tycho Epoch Photometry
revealed it to be very scattered, with even negative BT-VT at times,
suggesting that that mean value is not necessarily exact.  Neither
SIMBAD nor VizieR had much to add, though a 1980 paper gave a _Johnson_
V-I (ie _not_ a _Johnson-Cousins_ V-Ic) of +0.51 for V at 9.31.

V-Ic reddenned slightly towards minimum, with a range of +0.31 to +0.44,
ignoring 3 and 2 problematic and isolated measures (out of the 174 in
total) at the blue and red ends respectively (there is a little scatter
in the light curve on some nights).

On the whole, the spectroscopy and the photometric colours appear to be
just a little too early for a Cepheid, but none are that rigorous and
the lightcurve and period fit well enough.

Searches in many formal and informal variability and suspected
variability lists show that variability is not previously known, whilst
a cross identification check against many catalogues revealed no
infrared, xray or other exotic source coincident with this object.

Further monitoring is required to fully sample the lightcurve in order
to either confirm or deny this object's identity as a Cepheid, and if it
is a Cepheid, to help decide if it is a dCep or CW (W Vir) star.



John Greaves

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