Special Notice #329: Critical time for CV Campaign HST/COS target SDSS J100515.38+191107.9

January 29, 2013:  SDSS J100515.38+191107.9 is the upcoming target for the HST/COS CV Campaign (see AAVSO Alert Notice 471 [1] and AAVSO Observing Campaigns page (http://www.aavso.org/observing-campaigns [2]) for details and related Special Notices). Dr. Gaensicke writes:

"We are now entering the critical phase before the HST observations of SDSS1005+1911, scheduled for

                              Jan 31, 2013 01:17:09 to Jan 31, 2013 06:24:00 UT

"We will need to provide up-to-date V-band magnitudes tomorrow (Jan 30) morning EST. If weather permits, please give it a try, even though I know that this star is rather faint."

SDSS J100515.38+191107.9 is an SU UMa-type dwarf nova with infrequent outbursts. According to observations in the AAVSO International Database, it reaches V magnitude 18-19 at minimum (with one unsupported observation of 19.95 V at minimum), and it can be as bright as 12.3 V at maximum.

As instructed in AAVSO Alert Notice 471 [3], 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. Positive visual observations are welcome, as are visual fainter-than observations fainter than magnitude 14.0.

Coordinates for SDSS J100515.38+191107.9:   R.A. 10 05 15.41   Dec.  +19 11 07.5  (2000.0)

Charts may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp [4]).

Please report observations as soon as possible to the AAVSO International Database using the name SDSS J100515.38+191107.9. If an outburst is detected, please report observations immediately.   Many thanks!

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

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