[Aavso-photometry] Comp star c in HMXB 1930+53

[Gordon E. Sarty]

To all HMXBers: Can you please check your check star data in the field 
of the HMXB 1930+53. The comp star c at 19 32 44.543, 53 49 39.698 (see 
chart at http://www.usask.ca/psychology/sarty/Astronomy/LPH115_aavso.pdf 
) may be variable. See discussion with Ray Bloomer below.

Thanks
Gord

-------- Original Message --------
Subject: RE: CV Photometry
Date: Sun, 01 Jul 2007 08:59:26 -0400
From: Bloomer, Raymond <rhbloome at king.edu>
To: Gordon E. Sarty <gordon.sarty at usask.ca>
References: <C15E4787A1495844951D08DAD6EBCAEF6D8398 at kingmail.king.edu> 
<4685C731.9020403 at usask.ca>

Yes, C was the brightest of the comparison stars close to the variable.

Please do confirm with others.  As I said we had strange things going on 
with the filter wheel. It seemed to have a mind of it own:  one morning 
we leave with the filter certainly centered on the G filter, and then on 
boot up the next night it is between two filters, vignetting big time. 
WE eventually were careful to take the camera off at the beginning of 
the evening and confirm it position.  So I suppose the 0.4 mag jump was 
involved with that problem.  b and d did not show such a large jump, 
more within the scatter of a few hundredths of  magnitude.

I'll be interested to hear what others have to say.
Thanks,
Ray

________________________________

From: Gordon E. Sarty [mailto:gordon.sarty at usask.ca]
Sent: Fri 6/29/2007 11:00 PM
To: Bloomer, Raymond
Subject: Re: CV Photometry



Phooey, so by "C" you mean the star at 19 32 44.543, 53 49 39.698? If
so, everyone will have to revise their reductions. The stars b and d are
very red but if they are stable we'll have to use them. I'll be at the
AAVSO meeting this weekend and will ask around and see if anyone else
has noticed that c is variable.

I've been awarded more DAO time - an AN should be released sometime soon.

Gord

Bloomer, Raymond wrote:
> We had six full nights in May on LPH115 using the 41 CM and electrically
> cooled CCD.  We had filter issues, but most of our data is in the green.
>
> We have not finished with the data but I think it seems clear that
> comparison star "C" is variable.  Has anyone reported that?  We have
> seen unexplained 0.4 mag jumps in differences that included C.
>
> My differences of b and d were reasonably well behaved (SdDev = 0.01 or
> 0.02 mags).
>
> Ray
>