Re: GSC 540-84

[Arne Henden <aah@nofs.navy.mil>]

I find it hard to believe that you would have double min/max
with a pulsating star; if eclipsing binary, then I find the
bump at maximum hard to believe if it occurs on both eclipses.
   More likely is that this is a delta Scuti variable with
more than one period, so you are getting amplitude modulation
of the light curve.  Similar to the Blazhko effect for RR Lyrs.
I don't know the color of your variable to see whether it is
an RR Lyr or delta Scuti, though the effect is the same.
However, Blazhko is usually a long-period modulation and takes
many fundamental-period cycles before you can see the effects;
delta Scuti periods can modulate the light curve quicker.
Bottom line:  not all pulsators are as easy to study as eclipsing
binary systems.  Look at the MACHO papers on variable stars; they
are the Bible with regard to statistical studies of specific
classes.  Just look for Doug Welch's name through ADS.
Arne

Michael Koppelman wrote:
> I actually got a nice steady night last night:
> 
> http://www.lolife.com/astronomy/gsc540-84/gsc540-84_20030804.jpg
> 
> My comp star 1-sigma was 0.004! That's pretty good for me. The size of 
> the dots is the size of the error bars.
> 
> I'm still a little confused on this one. Using Patrick's period, which 
> was confirmed by Chris Lloyd we get this:
> 
> http://www.lolife.com/astronomy/gsc540-84/gsc540-84_phase.jpg
> 
> Using double that period we get this:
> 
> http://www.lolife.com/astronomy/gsc540-84/gsc540-84_dbl_phase.jpg
> 
> The data from 07/29/03 seems discrepant at the start and end of the 
> night if the period is not doubled. If the period is doubled it seems 
> like the end of that night of 7/29 has problems. If you assume that no 
> data has problems, something weird is going on.
> 
> Michael Koppelman
> 
> 
> 
>