Eclipsing binary?
 

While processing a few thousand images, these light curves appeared. It's rather noisy but the curve for "120-129" is reminiscent of a total eclipse with a duration of about an hour (the x axis is in days) and a depth of 0.05 magnitude. The depth is (almost certainly) too large to be an exoplanetary eclipse but could be that of a M dwarf. The primary star is currently believed to be constant --- it's a comparison for a known variable. There's nothing in GAIA DR2 to suggest that the primary is variable or multiple. I'll want to see at least one more eclipse before announcing it formally.

"138-129" is the magnitude difference between two other notionally constant stars and shows no structure above the noise. "V-129" is the light curve of the variable.

do you happen to know the designation of the star you observed in any of the catalog?

[QUOTE=firejuggler;491539]do you happen to know the designation of the star you observed in any of the catalog?[/QUOTE]Yes, but I'm not going to reveal it until I've more evidence one way or the other. You can already deduce that it has a GAIA-DR2 designation.

So, i'll suggest checking for starspot or contamination
[url]https://blog.planethunters.org/2013/02/11/starspots-and-transits/[/url]


Sorry if you already though of those two. after all, i'm no expert.

[QUOTE=firejuggler;491578]So, i'll suggest checking for starspot or contamination
[url]https://blog.planethunters.org/2013/02/11/starspots-and-transits/[/url]


Sorry if you already though of those two. after all, i'm no expert.[/QUOTE]Thanks. A nice page of which I was not previously aware.

[QUOTE=xilman;491580]Thanks. A nice page of which I was not previously aware.[/QUOTE]

Yes, interesting link- if the x-axis is in days, though, wouldn't that imply an incredibly fast rotation of that star (120-129)? Or am I misunderstanding something...again...

Neat stuff, though.

Norm

[QUOTE=xilman;491575]Yes, but I'm not going to reveal it until I've more evidence one way or the other. You can already deduce that it has a GAIA-DR2 designation.[/QUOTE]

Have you queried [url]https://asas-sn.osu.edu/variables[/url] ? They have 27000 things on their list, though I think at least one of their sites is southern-hemisphere so won't have much overlap on the sky with things observable from Cambridge.

I've found the Gaia-DR2 photometry flags not terribly useful (that is, when I look up objects from sky-survey-group papers about new variable stars in DR2, they aren't inevitably catalogued as variables), but I've been using sky.esa.int and they might be better through the main interface.

[QUOTE=Spherical Cow;491644]Yes, interesting link- if the x-axis is in days, though, wouldn't that imply an incredibly fast rotation of that star (120-129)? Or am I misunderstanding something...again...

Neat stuff, though.

Norm[/QUOTE]Nope, the event takes about an hour. That's why I'm sure that, if real and not some instrumental effect, that it's an eclipse --- fairly typical for a close orbiting companion.

Paul

[QUOTE=fivemack;491645]Have you queried [url]https://asas-sn.osu.edu/variables[/url] ? [/QUOTE]I hadn't but have now. Nothing relevant with 10 arcmin. Thanks for the link, of which I wasn't previously aware.

There's a possible hint of something similar in later data but much more careful examination is required before a discovery can be claimed.

Looks very much like an eclipsing binary with a primary eclipse of ~ 0.025 mag, a secondary of 0.01 mag and a period of 0.2305 days. The attached image is the phase plot folded at the assumed period and smoothed into bins of size 0.005. Something over 5000 measurements into that plot so each bin is the average of about 25. The secondary minimum is barely visible in the noise of the unsmoothed data.

Nice plot. Cool result.