Saturday, April 13, 2013

Mystery Star KIC 9406652 at Planet Hunters


Q10 Time plot for KIC 9406652 by Kian Jek

Forum Talk member Penn_gwenn flagged this star in Kepler Q2. It immediately attracted interest from forum members, Zoo3hans, Kian Jek, Nighthawk_black, Cappella and others as a possible Dwarf nova or Heartbeat binary. You can see superhump-like features in the time plot above. KIC 9406652 is currently being investigated by the Kepler Guest Observer program for further analysis. No one quite knows what exactly this star is.

Kian Jek

I believe this might be genuine. There are APOs of around 20-30 millipixels in the source FITS file, but the brightening points in the direction of the target. And there is no apparent source in that direction. The APOs represents the flux shifting away from the brighter neighbor IMO:



I suspect this could be an SS Cygni type of dwarf nova, from the shape and frequency of the outbursts - they are more frequent and do not exhibit the super-outbursting behavior of the SU UMa types we've seen previously. There are superhumps noted during the descending limbs of an outburst, sometimes stretching into the quiescent periods, with a period of approximately 6 hours. I'll do a little more poking around.


The region from which I took the sample to find the superhump period is here:

and here's where it comes from, in Q10:

Backing up a bit, here's the entire light curve:

What just occurred to me is that the lowest flux levels seen here are true minimas - they are not due to data gap problems - the flux level of ~0.5 seems to be the actual base flux level, and therefore this DN seems to spend a lot of its time at about 2x its lowest brightness. This type of behavior is perhaps more accurately described as a UGZ or a Z Camelopardalis type of dwarf novae rather than a UGSS (or SS Cygni type).
 Caveat: I am not a real astrophysicist. EIKAAILOW™ (Everything I Know About Astrophysics I Learned On Wikipedia).
This is interesting because IIRC we have already found 2 examples of UGSU and 1 UGSS (although they are background DNs) and this one, which seems like a real target, is a UGZ, and thus completes all the major types of dwarf novae discovered by citizen scientists in the Kepler FOV.

Daryll LaCourse (Nighthawk_black):
Keppixseries from the target pixel files support this interpretation; the outbursts flood the optimal aperture and to a lesser extent the surrounding halo pixels:

Q5:

FULL

Q10:

FULL

You can follow this star on Planet Hunters forum Talk here.

Tuesday, April 2, 2013

Unlisted 1.84x RE Super-Earth Transiting KIC 8499940

Q14 light curve for KIC 8499940 at Planet Hunters

Planet Hunters forum Talk member Sean63 flagged this long period transit in Kepler Quarter 14. It is not listed on the Kepler Threshold Crossing Events (TCE)  table.

Kian Jek:

Q14 event appears to be the only transit seen in all the quarters. The modeled transit gives an estimated period of 1387 d + 540/-280, so it looks like a pretty long-period PC.


The transit curve also estimates a 1.84x RE super-earth, at 2.9AU and Teq of 158K.

Kepler Q14 also has more than its share of cosmic ray hits. Here is Kian's comments on this possibility:

 I just checked the FITS file. It's hard to tell for sure. Turns out there IS a cosmic ray hit, an isolated one but in the OA. However it is right in the middle of the transit as circled.

The others we have seen were at the very start of the dips. What the CR hit does is to cause a momentary spike. The CCD module detects these spikes and then adjusts the level to compensate for it. But because I think the circuitry is overloaded, what usually happens is that although the spike is removed, subsequent cadences are adjusted down instead, creating the impression of a dip.

I'm not sure. We'll have to look for repeats.


 
 
 You can follow the discussion on this possible planet transit on Talk here.






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