[vsnet-chat 7547] Re: variable in OTJ16... field?

[substellar at Safe-mail.net]

-------- 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