[vsnet-chat 7546] Re: variable in OTJ16... field?

[substellar at Safe-mail.net]

Woah, I thought I'd been kicked off of this chat list for upsetting the observers with facts and unwelcome crap like that?

Always get to receive the interminable vsnet maillist posts, though, censorhip is unidirectional.  Time to dig the damn filters out again...

Anyway, humping in an adjacent field star?  Similar period to the target star?  Two arcmin away from the target?

There's some history of apparent "sympathetic" variability in field stars, it's led some allsky surveys for said to publish nonexistant variable stars before now.

Basically, I think, it is the brighter, varying, object, when bright enough, and depending upon your image scale and field width and setup, messes around with your _background_, and this aperture photometry thingy people use includes the background in the aperture whilst determining a stars magnitude, so what you're probably picking up is the fact that your star is constant but the background is pulsing from stray ambient brightening of the sky background due to the not unclose the target.

Something like that anyway.  It's usually a much lower amplitude a variation than the true source.  But it's also somewhat system (observing setup scale and possibly even kit etc) dependent.

Cheers

John

-------- Original Message --------
From: Rudolf Novak <exebece at gmail.com>
Apparently from: vsnet-chat-bounces at ooruri.kusastro.kyoto-u.ac.jp
To: cba-chat at cbastro.org, vsnet-chat at ooruri.kusastro.kyoto-u.ac.jp
Subject: [vsnet-chat 7544] variable in OTJ16... field?
Date: Sat, 10 Jul 2010 00:01:30 +0200

> Dear colleagues,
> 
> would you please check variability of USNO-B1.0===1020-0302581? On my
> images the star seems
> to be humping. I prepared some info to the blog:
> 
> http://ccder.blogspot.com/2010/07/variable-star-in-field-of.html
> 
> 
> With best regards
> 
> Rudolf
> 
> P.S. I checked the variability of other star reported by Gianluca and
> found no dip like effects reported by him. I'd ve very interested
> about their nature, plase drop a note if you have any idea (off the
> chat probably)... Now another run of OTJ16 is ongoing...
> 
> -- 
>   ----------------------------------------------------
> Rudolf Novak
> Brno University of Technology
> Czech Republic http://ccd.astronomy.cz