[vsnet-chat 7359] Re: MisV1396 - remarkably blue star with a rare variation

[arne]

Seiichi Yoshida wrote:
> Dear colleagues,
> 
> One of the recent new variable stars discovered in the course of the
> MISAO Project, MisV1396, is remarkably blue.
> 
> MisV1396
>   R.A.  01h07m22s.96
>   Decl. +57o08'01".8  (2000.0)
>   Mag.  11.29-11.72C
>   Type  E:
> = GSC 3677-00180  01h07m22s.94 +57o08'01".8  Error:0.3"  Mag:10.86  MagError:0.41  Band:1  Class:0  Plate:01W2  Flag:T  Epoch:07 NOV 1983
> = GSC 3677-00180  01h07m22s.97 +57o08'01".7  Error:0.2"  Mag:11.40  MagError:0.40  Band:1  Class:0  Plate:036D  Flag:T  Epoch:11 OCT 1983
> = USNO-A2.0 1425.01555531  01h07m22s.970 +57o08'01".94  Mag(R):12.2  Mag(B):11.8
> 
> http://www.aerith.net/misao/data/misv.cgi?1396
> 
> The RGB composite image from DSS I, R and Bj images is available at
> the web page above, which shows MisV1396 is remarkably blue. The
> USNO-A2.0 color is B-R = -0.4 mag.
> 
> MisV1396 faded only once by the MISAO Project observations. It is
> almost constant the other days.
> 
> The following NSVS light curve shows MisV1396 is almost constant, or
> maybe it shows a small irregular variation.
> 
> http://skydot.lanl.gov/nsvs/star.php?num=1728453&mask=18708
> 
> Is this star something special?
> 
This star is not remarkably blue as far as I can tell.  For example,
the TASS patches catalog lists it as V=11.51, (V-Ic) = 0.41.
Tycho (at its limit) gives V=11.524 (B-V) = 0.275
2MASS gives J=10.704, H=10.662, K=10.592
All of these are consistent with approximately an F0V star.

Please do not rely on USNO-A or USNO-B photometry.  Among other things,
11th magnitude stars are heavily saturated on the Schmidt plates.  I would
also not consider this star variable based on a single discrepant datapoint,
especially since NSVS does not show any variation.  There are *many* ways
in which a single image can yield a discrepant magnitude.
Arne