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Potential Variable

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Adam Biery
Potential Variable

Hello Everyone,

I have prepared a variable star for submission to VSX, and would like opinions on it. It is possibly a pulsating variable, or RRC. The period I have found is 0.499197, an amplitude mag of ~0.5. Here are all some 'Other Names':

2MASS J01515157+3552486
CSS_J015151.4+355248
GSC 00080-09043
SDSS J01515068+355243.2
USNO-B1.0 1258-0027686
WISE J01515071+3552433

The magnitude of the brightness is quite low, at around 16.5-17 which is why I believe there is very little data on this specific object. 

Originally found with ROTSE-III, coordinates - J015150.76+355243.8.

I would appriciate any feedback or comments! 

Thanks!

-Adam Biery

 

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Sebastian Otero
Sebastian Otero's picture
A blended galaxy

At the position you gave there is a very faint star with g= 20.0; r= 18.8; V= 19.4.
The CRTS data is around 18.4 CV not 17.0 as in the plot and the period looks spurious. It is a multiple of 1 d. I don't see that the CRTS data may miss the minimum (you plot all the CRTS dat as if they were at the maximum in the phase plot, with a gap matching your minima).
How did you determine the zero point?
12" away there is the 17th mag. galaxy PGC 2071405 and that will be blended in ROTSE and ASAS-SN.
This is what you are detecting IMO. Most of the light comes from this galaxy and thus it is not a variable star.
CRTS light curve.

Cheers,
Sebastian

GDonnelly
About periods that are multiples of one day

Hi Sebastian,

I have noticed that with various period-fitting algorithms (a spline fitter, box least squares, phase dispersion minimization...), there seems to be a bias toward integer or half integer multiples of one day, especially 1/2 day and 1 day periods. Is this something that you have noticed before as well? Would you happen to know what may cause this bias? I always suspected it was due to the actual scheduling of the data usually being based on day intervals. 

Regards,

Grant

Sebastian Otero
Sebastian Otero's picture
Correct

Yes, you are right, usually surveys have a cadence of one or a small cluster of observations per day or every two or three days, this causes these frequencies to come up. This doesn't mean that there are no variable stars with periods that may be an integer fraction of 1 day or a multiple. But they will usually show a cleaner light curve.
Always check for blending when using survey data.

Cheers,
Sebastian

GDonnelly
Thanks for clearing that up!

Thanks for clearing that up!

Sebastian Otero
Sebastian Otero's picture
Identifiers mixed

Also check that you are mixing identifiers for both objects. Some show the galaxy's position and others the star's position. You should be careful when cross-matching objects. Since they are coordinate-based identifiers, it is easy to notice.

Cheers,
Sebastian

GDonnelly
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