Re: GSC 1040-399 + new variable

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

Hmmm.  30th order polynomial?  You hardly have enough points
to uniquely solve for such a beast, much less get a least-squares
solution!
   67 minutes, 133 minutes, and 3 minutes are all commensurate to
first order.  Since John indicates this is a 5arcsec double, I am
more inclined to believe centroiding errors leading to flux
"sloshing around" in your measuring aperture, perhaps depending on
seeing variations.  Try using a much larger aperture to minimize
centroiding problems and see if the variations decrease or stay the same.
Arne

Michael Koppelman wrote:
> I opened this up in TS and fit a 30th order polynomial to it. It looked 
> sine wave-ish. I grabbed the times of the maxima and calculated the 
> difference. The average was 0.0463 with a std dev of 0.003. The I ran 
> the Fourier on it and it found a strong period at 0.0478. There is a ton 
> of noise in it but the data does phase somewhat convincingly at that 
> period. It phases even more convincingly at twice that period at 0.0956.
> 
> These two periods are 67 minutes and 133 minutes respectively. My 
> exposures were every 186 seconds or so. It doesn't appear that this is 
> an alias, but I guess I wouldn't know. My period error is at a much 
> shorter interval so if the aperture was moving around due to something 
> periodic like that, you'd think the signal would be closer to that time, 
> which is I think 8 minutes or something. Those are the only two things I 
> can thing of off the top of my head that could be me introducing a 
> periodic error.
> 
> So I guess I would conclude that the data has a periodic signal in it. 
> This could be actual variation or just errors I don't know about, 
> perhaps relating to the companion that 2MASS can see about 5" away 
> (which John Greaves pointed out). There is no sign of that star in my 
> data. The amplitude on this is miniscule, around 0.04 or so, so I guess 
> anything is possible.
> 
> Cheers,
> Michael Koppelman
> 
> 
> On Wednesday, July 16, 2003, at 10:56 AM, Arne Henden wrote:
> 
>> By eye, it looks like it might be periodic,
>> which is good; periodic and low amplitude often indicates delta-scuti.
>> Color information might help in the identification.
> 
> 
> 
>