January 24, 2013: Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471), the next HST COS target is the SU UMa-type dwarf nova SDSS J100515.38+191107.9. HST COS is scheduled to observe it:
SDSS J100515.38+191107.9 2013 January 31 01:17:09 through 06:24:00 UT
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.
Your observations are crucial, as the HST planners will decide whether to observe SDSS J100515.38+191107.9 based on your observations. They will need to know whether the system is in quiescence, as if it is too bright it will damage the instrumentation and the observations will be cancelled. They will likely make their decision sometime on January 29.
As instructed in AAVSO Alert Notice 471, 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. At 18-19 V at minimum, SDSS J100515.38+191107.9 is likely too faint for positive visual observations at minimum. If positive visual observations are possible, however, they 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).
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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