[vsnet-chat 7548] Re: variable in OTJ16... field?

[David Boyd]

I've just analysed 5 nights (5-9 July) data from Bart and myself on the putative 
new variable GSC 967 904. All from essentially one longitude so there are strong 
aliases. It looks like a genuine variable unrelated to the nearby superhumper.

The sinusoidal fitting methods in Peranso all favour a single cycle period of 
0.169d with amplitude 0.08mag. ANOVA seems to prefer a longer double cycle 
period. No colour information seems to be available yet.

Regards,
David

----- Original Message ----- 
From: <substellar at Safe-mail.net>
To: <novak at hvezdarna.cz>; <vsnet-chat at ooruri.kusastro.kyoto-u.ac.jp>
Sent: Monday, July 12, 2010 9:24 AM
Subject: [vsnet-chat 7547] Re: variable in OTJ16... field?


> -------- Original Message --------
> From: Rudolf Novak <exebece at gmail.com>
>
>> as I did. And - it seems that the period is (fortunately ;) different
>> too.
>
> Ah, well, that is good news.
>
> Double check the period isn't a close multiple or fraction of the superhump 
> period.  Twice or half for example.
>
> Then once you've checked that, note the amplitude.
>
> Put the graph up somewhere, you can keep the period secret if needs be.
>
> If the period is between 0.1 days or 0.05 days or in that sort of area, it 
> could be a delta Scutid or beta Cepheid.
>
> If the amplitude is 0.1 to 0.2 magnitudes and the period is less than a day to 
> a very short period, it could also be one of those.
>
> If slightly longer than 0.1 days, it could be an SX Phe or again a beta 
> Cepheid or even an SPB, they all behave quite similar, coz they're a 
> 'gradation' across that part of an instability for blue to yellowwhite 
> Population I stars
>
> If the lightcurve is evolving in shape, and real and valid signal, it could be 
> a delta Sct or beta Cep with multiperiodicity.
>
> 2MASS colours don't really support those types, but it depends exactly how 
> much interstellar extinction there is in this part of Hercules, though for the 
> J-Ks this thing has that'd be a lot.
>
> If the period is half to a whole day, and even with the colours, there's a 
> vague possibility of a gDor (gamma Doradus) star, some shorter period ones of 
> those have been turning up in Kepler and CoRoT compared to the traditional 1+ 
> day period(s) (multiple periodicity in those often).
>
> If the period is over a day or more and amplitude about 0.2 magnitudes to less 
> and somewhat cleanly and regularly sinusoidal, could be a starspot rotator 
> which takes in RS CVn, BY Dra an alpha2 Canum Venaticorum stars (though the 
> latter is not so much starspots as bright spots).  Once period gets over a day 
> you can get ellipsoidal variables included into the mix at low amplitudes.
>
> So, you need good phase coverage, several cycles' coverage to ensure any 
> lightcurve morphology is consistently repeated, or not, and if period is short 
> that'll mean longitudinally distributed observers, and then you may never know 
> whether bcep/spb/dsct/sxphe/gdor without a spectrum, although if the period is 
> about 0.1 day or less or just over, bcep/dsct/sxphe is something you could 
> likely narrow it down to.
>
> A phaseplot somewhere will help you decide, as I say you can keep the period 
> quiet if you wish.  You've telled everyone where it is now, though, but on the 
> positive side, others who have been monitoring the UGSU stars might feel 
> generous enough to get a lightcurve from their data for this star too and pass 
> it on to you, which'd help phase coverage.
>
> If it's multicolour photometry you could all club together and try an IBVS, if 
> not well PZP takes new variables found in target fields' papers, and referees 
> 'em (which is good, not bad, because if one is going to publish, one want's 
> one's gaffs caught pre-print, mostly).
>
> Cheers
>
> John