Skip to main content

Special Notice #349: HST/COS Observations CANCELLED for SDSS J154453.60+255348.8

April 30, 2013:  Further to AAVSO Alert Notice 471 ( and AAVSO Special Notice 348 (, HST/COS was scheduled to observe the eclipsing dwarf nova SDSS J154453.60+255348.8 tonight:

SDSS J154453.60+255348.8 2013 May 1 04:06:20 through 08:17:24 UT

HOWEVER, THESE OBSERVATIONS HAVE BEEN CANCELLED. PI Dr. Boris Gaensicke writes, "We had a telecon with STScI a few hours ago, and due to the recent brightening, and the relatively poor knowledge regarding the long-term light curve and the variability in the UV wavelengths, we all concluded that it will be better to err on the safe side. Sigh... But then, we managed to get 25 observations done safely, and with the unpredictable behaviour of CVs, it had to happen sooner or later."

Even though the HST observations have been cancelled, please continue to observe SDSS J154453.60+255348.8 nightly until the outburst is over to further our understanding of this system. The system continues in outburst at V~15.8-17.5, according to observations reported to the AAVSO International Database by eight observers. SDSS J154453.60+255348.8 is V=<18 at minimum and can be as bright as V=15.7 at maximum.

There is a possibility that this system may be rescheduled for observation by HST/COS later in the program, but that decision will not be made for a few months.

Coordinates (2000.0)
SDSS J154453.60+255348.8    R.A. 15 44 53.60   Dec. +25 53 48.9

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 J154453.60+255348.8. 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:

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