February 12, 2013: Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471) and AAVSO Special Notice #330 (http://www.aavso.org/aavso-special-notice-330), HST/COS is scheduled to observe BB Dor on:
BB Dor 2013 February 13 20:57:03 through 23:53:50 UT
BB Dor is a novalike (VY Scl) cataclysmic variable. It is currently at magnitude ~V=18 and not likely to pose a hazard to HST but your observations are urgently needed for correlation with the HST/COS data.
HST/COS is then scheduled to observe the dwarf nova SDSS J143544.02+233638.7 on:
2013 February 15 22:05:53 through February 16 02:16:17 UT.
At V=18.2 at minimum, its maximum brightness is unknown. Observations are crucial now through February 16, and especially so through February 14, when the HST/COS scheduling team will make the final decision whether to observe this system.
Then, HST/COS is scheduled to observe the dwarf nova HM Leo on:
HM Leo 2013 February 22 07:17:20 through 14:22:37 UT
At V=17.5 at minimum and V=13 at maximum, it will be essential to know whether HM Leo is in outburst. In outburst it could damage the HST/COS instrumentation. Your nightly observations now are important and will be crucial in the few days prior to February 22.
As instructed in AAVSO Alert Notice 471, for CCD observers, simultaneous photometry [shortly before, during, and after the HST observations] would be ideal. For the magnitude estimates, a nightly V measurement from now through the HST observations and a day beyond would be best. If positive visual observations are possible, they are welcome, as are visual fainter-than observations fainter than magnitude 15.0.
BB Dor R.A. 05 29 28.59 Dec. -58 54 46.3
SDSS J143544.02+233638.7 R.A. 14 35 44.02 Dec. +23 36 38.7
HM Leo R.A. 09 38 36.99 Dec. +07 14 55.0
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 names BB Dor, SDSS J143544.02+233638.7, and HM Leo, respectively. 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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