Re: GSC 540-84

["Shawn Dvorak (Rolling Hills Obs)" <rollinghillsobs@cfl.rr.com>]

The range is 0.4 mag which, if I'm not mistaken, is fairly large for a delta
Scuti.  V-Ic from TASS is 0.34 and B-V from Tycho is 0.16.

Shawn


----- Original Message ----- 
From: "Arne Henden" <aah@nofs.navy.mil>
To: "Michael Koppelman" <lolife@bitstream.net>
Cc: "Tass" <tass@listserv.wwa.com>
Sent: Monday, August 04, 2003 6:58 PM
Subject: Re: GSC 540-84


> 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
> >
> >
> >
> >
>
>
>