I found this object several months ago while looking for high-pm stars: I'm not much of a variable star observer, so don't expect me to be an expert in this field at all! What I do know, however, is that this isn't a usual occurence.
A star at 0.0061, +49.2211 (00 00 01.473, +49 13 16.10) which was identified previously as a (false) high-PM candidate by the Initial Gaia Source List, seems to have disappaered. I noticed a star a couple of arcseconds away, but realized that this couldn't be the star, as this one was detected in exactly the same place in 1951, 1972, and 1991. Then, it disappears. 2MASS doesn't detect it, Gaia doesn't detect it, even PANSTARRS doesn't detect it!
It seems that this object rapidly faded from V=~20.5 to V>24 without any hint of a supernova or any other identifying features. It could be explained as a sort of long-period variable, except in the 1951, 1972, and 1991 images it remains at a very constant brightness of R=~20.3.
First of all, does anyone have any images of this region of sky, and does anyone know any possible mechanisms that could cause a star to suddenly vanish? Any explanation would be greatly appreciated, as this has been bothering me for months.
~Sam
(By the way sorry if I'm posting to the wrong place. It doesn't seem there's a good place to ask about unusual variable phenomena if you didn't actually observe them!)
Judging by the star's repeated detection in a selection of images spanning 1951 to 1991, yet its appart abscence from ones thereafter, I would venture it might be an unrecognized member of the R CrB class with the star entering a very protracted minimum phased after the early 1990's. A second, although far less likel, possibility, is it being similar to FG Sge which remained at a relatively constant brightness for decades, then faded many magnitudes never to recover. These are, of course, only the simplest solutions that come most quickly to mind. There cettainly are countless others.
J.Bortle (BRJ)
Thanks for the feedback! I initially suspected some kind of late-type extreme variable of that sort, but this star seems to be F or G type (F3 by the USNO-B colors) and definitely doesn't have a WISE presence. It seems these other variable types are mostly AGB stars which would have emission in infrared (although I suppose it wouldn't be visible in WISE anyway if this was during a minimum)
A couple other problems with that is that both of those are giant and supergiant stars experiencing it. Assuming Vmag 20.5 is its normal brightness, it would have to have an absolute magnitude of dimmer than 3 to be inside the milky way's disk (<100,000 LY). Furthermore, both of these variable types are also fairly short-lived, with dimming on R CrB stars almost always lasting less than 6 months it seems. Even if PANSTARRS and Gaia were the only surveys to detect it, they imaged the area multiple years apart, and the odds of this star being at a minimum during both of them seems like less than 1%.
Here's a basic light curve of the object: http://i.imgur.com/8TRv3QI.jpg I'm working with someone to try and find further archival images of this region of the sky, so that should be improved in the future.
~Sam
This star had also dimmed markedly over a long period of time, and the theory is it has become engulfed in a condensing nebula of absorbing dust. The problem here is also that your object is so faint, it is beyond the reach of most, if not all amateur observers at AAVSO!
Mike
Hi Sam,
Cataclysmic variables can experience deep, aperiodic fading events if the mass-transfer rate drops off. These fades can last for years, even decades. For example, one AM Herculis-type star that I've been following was undetectably faint in deep photographs taken in 1953, 1983, and 1991, and in 2003, SDSS measured it at g = 21.7. But at some point between 2003 and 2007, it transitioned into a stable bright state, and it has regularly peaked at V~16.5 ever since. The extra luminosity comes from accretion onto the WD.
So I think that a CV is a plausible explanation.
Colin
The POSS-I and POSS-II plates are digitized and available from
http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/icas/fchpix
among other servers. The USNO server doesn't include the 1970 plates, which are probably the Luyten plates. As others have said, there are some variable star types that would exhibit that kind of fading behavior, but I'd suspect just plate limit issues rather than any fading. Other than POSS, there were a few deep photographic surveys of limited area that might give information. Since the 1990's, there were some digital surveys (especially the CFHT Megacam data) that might be useful to search. I doh't know if SDSS, PanSTARRS, PTF, CRTS, etc. would be useful.
Good luck on your project!
Arne
Arne