May 13, 2013: Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471 ) and AAVSO Special Notice #351 (http://www.aavso.org/aavso-special-notice-351 ), HST/COS is scheduled to observe the dwarf nova SDSS J153817.35+512338.0:
SDSS J153817.35+512338.0 2013 May 16 22:44:06 through May 17 02:14:05 UT
The HST team will be making a final decision on observing SDSS J153817.35+512338.0 based on the observations of May 13/14 and 14/15, and observations from the following two nights will also be essential. Close monitoring of 1RXS J105010.3-140431 through May 18 is requested. SDSS J153817.35+512338.0 is V=18.6 at minimum and its magnitude at maximum is unknown.
After SDSS J153817.35+512338.0, the next target will be the SU UMa-type dwarf nova DT Oct:
DT Oct 2013 May 23 23:31:07 through May 24 02:05:03 UT
This date is revised from the preliminary date given in AAVSO Special Notice #351. Giving SDSS J153817.35+512338.0 highest priority, please also monitor DT Oct; close monitoring May 17 through 25 is essential. DT Oct is V=16.5 at minimum and V=11.8 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. 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.
SDSS J153817.35+512338.0 R.A. 15 38 17.31 Dec. +51 23 38.0
DT Oct R.A. 18 40 52.31 Dec. -83 43 10.0
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 SDSS J153817.35+512338.0 and DT Oct, 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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