(cba:news) Fwd: monitoring of SDSS1538

[Joe Patterson]

Hi CBAers,

Anna has sent this request.  The presence of such a hot WD in this 
short-period binary is indeed a puzzle, and it's possible we could 
contribute to its solution.  The estimated magnitude is 18.6, so it's a 
daunting challenge for time-series photometry (unless it brightens). 
However, some of you probably are able to get decent nightly brightness 
estimates - by averaging, long exposures, etc.

I recommend unfiltered since you're likely to need every photon you can 
get.  Be sure to specify your (primary?) comp star, so she can convert 
it to a quasi-calibrated magnitude.  But I don't think a real time 
series is feasible or even wanted (I'll ask).

joe p


-------- Forwarded Message --------
Subject: 	monitoring of SDSS1538
Date: 	Thu, 15 Feb 2018 11:22:33 +0000
From: 	Pala, Anna <A.F.Pala at warwick.ac.uk>
To: 	jop at astro.columbia.edu <jop at astro.columbia.edu>



Dear Joe,


We have been awarded some HST time to observe SDSS J153817.33+512238.0, 
a short period CV (Porb = 93.11 min) that hosts an unexpectedly 
hot white dwarf (T ~ 30000K). This high temperature could be a clue of a 
nova eruption within the past few 1000 years and the HST observations 
will help us in identifying possible ashes and the expanding 
circumstellar gas shell expected in this case.
The HST scheduling team requires us to provide ground based monitoring 
in order to asses the quiescent state of the target prior the HST 
observations, which should be scheduled in the window March 27 - April 
10.More information on the program can be found at this link:
http://www.stsci.edu/cgi-bin/get-proposal-info?id=15316&observatory=HST

It would be very helpful if the CBA could help us in monitoring this CV.
Would it be possible to release an alert notice about this observations?

To asses the quiescent state we would need nightly V/unfiltered 
observations starting on the 23rd of February, a more intense monitoring 
in the period March 27 - April 10, and then nightly observations again 
through the end of April.

SDSS1538 is a northern target and is quite faint in quiescence:

RA                       Dec                V
15 38 17.3410    +51 23 38.04  18.6

Please, let me know if you need more information.


Thank you very much for your help.


Kind regards,

Anna


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