[Aavso-photometry] 1930+53

[arne]

Jim Roe wrote:
> I've been monitoring this star for the past month in V and Ic.  Most of 
> the time Ic is brighter than V but on two recent occasions, V has come 
> out brighter than I.  I seem to be the only one recording this as I see 
> looking at the light curve generator.  I've looked carefully at my 
> images and don't see anything strange, but I'm wondering if this could 
> be 'normal' behavior for this star ( a High Mass X-Ray Binary )?  Should 
> I look harder at my images?
> 
 From my SRO photometry, DM+53_2262 is basically a colorless object on
the Johnson-Cousins system, so B=V=Rc=Ic within a few hundredths.
Your recent photometry is interesting, in that you have Ic constant
over two nights (October 4 and October 5) at about Ic=10.36,
while the V measures vary from 10.29 to 10.47 or so. Are these
variations real? Can this star vary by 0.2mag over the course
of 24 hours, and only at V?  My gut feeling is "no", and one
concern I have is that your V-band reported errors are quite
a bit larger than your Ic-band reported errors.  I wonder why?


Off-hand, I can't think of anything physical that would cause V to vary
but leave Ic alone.  So I'd look harder at your images first, especially
flatfielding.  Look at the other stars I calibrated in the field,
using the same base comparison star (9.684), and see if you get the
magnitudes I published, and on both nights.
Arne