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Alert Notice 423: Request for observations of V455 AND in support of HST observations

August 30, 2010: Dr. Paula Szkody (U. Washington) has requested the help of AAVSO observers in monitoring the WZ Sge-type cataclysmic variable V455 And in support of Hubble Space Telescope ultraviolet spectroscopic observations scheduled for 6:55-15:20 2010 September 11 UT (the night of Friday, September 10/11) (JD 2455450.78819 - 2455451.13889). Observations are requested beginning immediately and continuing through September 20. This monitoring is crucial to these observations.

The primary purpose of the monitoring is to know whether V455 And is in quiescence; if it is in outburst it will be too bright for the HST instrumentation. The decision whether to go forward with the HST observations will be made the evening of Thursday, September 9/10, so the nights of September 8/9, 9/10, and 10/11 are the most critical for observations to be reported. Positive visual or V observations are preferred if at all possible, but fainter-than observations below V=14 are useful (<14.0 or fainter). Therefore, nightly observations are sufficient for now; 2-3 observations per night are requested during the nights of September 8/9 through 12/13, after which nightly observations may be resumed.
 
For CCD observers, Dr. Szkody writes, "[We] will also be summing the spectra to obtain UV light curves. Simultaneous photometry [shortly before, during, and after the HST observations] would be great for CCD observers. 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."

During quiescence V455 And is around magnitude V=16. According to observations in the AAVSO International Database, the last outburst of V455 And occurred September 5, 2007, when it reached visual magnitude 8.0 and was brighter than about magnitude 15 until November 2007.

V455 And (AUID 000-BDC-667) is located at the following (J2000) coordinates:

     RA: 23:34:01.45   Dec. +39:21:40.9

Charts for V455 And may be plotted using AAVSO VSP:
http://www.aavso.org/vsp

Please report all observations of V455 And to the AAVSO as V455 AND.

Thank you for your observing efforts and valuable observations!

This AAVSO Alert Notice was prepared by Elizabeth Waagen.

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