Alert Notice 471: Cataclysmic variables to be monitored for HST observations

September 20, 2012: Drs. Boris Gaensicke (Warwick University), Joseph Patterson (Columbia University, Center for Backyard Astrophysics), and Arne Henden (AAVSO), on behalf of a consortium of 16 astronomers, have requested the help of AAVSO observers in monitoring the ~40 cataclysmic variables in the table below in support of Hubble Space Telescope observations in the coming months. The HST COS (Cosmic Origins Spectrograph) will be carrying out far-ultraviolet spectroscopy of ~40 CVs sequentially, with the aim to measure the temperatures, atmospheric compositions, rotation rates, and eventually masses of their white dwarfs.

The primary purpose of the monitoring is to know whether each target is in quiescence immediately prior to the observation window; if it is in outburst it will be too bright for the HST instrumentation. Based on the information supplied by the AAVSO - by you, our observers - the HST scheduling team will make the decision (usually) the evening before the scheduled observing time as to whether to go forward with the HST observations. Thus, your observations will be crucial.

***THE FIRST TARGET TO BE MONITORED IS SDSS J164248.52+134751.4. It is scheduled for 2012 October 11-15 (JD 2456212-2456216); the exact time will be announced closer to the date in an AAVSO Special Notice. During quiescence SDSS1642+1347 is around magnitude V=18.6. Coordinates are given in the table.

Nightly observations are requested beginning immediately and continuing through at least the end of October.***

For CCD observers, simultaneous photometry [shortly before, during, and after the HST observations] would be ideal. B filter would be best for a light curve, although for the magnitude estimates, a V measurement would be best. An uninterrupted light curve would be better than cycling between filters. Visual observations are welcome for any targets bright enough.

Charts for the targets may be created using the AAVSO Variable Star Plotter (VSP) at http://www.aavso.org/vsp. Photometrists should use the appropriate data table supplied for each target.

Please submit your observations to the AAVSO International Database as soon after making them as possible. If you see the target in outburst, please contact the AAVSO immediately and post a message to the Observations and Campaigns & Observations Reports forum (http://www.aavso.org/forum). Please use the Primary name in VSX given in the table when submitting your observations to the AAVSO International Database.

This campaign is being followed on the Observing Campaigns page (http://www.aavso.org/observing-campaigns).

Your observations and their timely reporting are critical to the success of this campaign. Many thanks for your contributions!

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

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