Skip to main content

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

Due to the New England winter storm currently affecting the area, phone coverage at the AAVSO may be much reduced until Wednesday. The staff is still available via email, and we suggest using that method to contact us if you need assistance.

January 29, 2013:  SDSS J100515.38+191107.9 is the upcoming target for the HST/COS CV Campaign (see AAVSO Alert Notice 471 and AAVSO Observing Campaigns page ( 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, 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 (

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.


Information on submitting observations to the AAVSO may be found at:


A Special Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL:


AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484