Special Notice #354: DT Oct obs crucial now, GW Lib and V1108 Her next targets

May 22, 2013: Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471) and  AAVSO Special Notice #353 (http://www.aavso.org/aavso-special-notice-353), HST/COS is scheduled to observe the SU UMa-type cataclysmic variable DT Oct TOMORROW:

DT Oct  2013 May 23 23:31:07 through May 24 02:05:03 UT

The HST team will be making a final decision today on observing DT Oct based on the observations of the past few days. Tonight's and tomorrow's obervations will also be essential.
 
Close monitoring of DT Oct through May 25 is requested. DT Oct is V=16.5 at minimum and can be as bright as 11.8V at maximum. It appears to have had a brief outburst 2013 May 16-18 UT, when it reached 13.0 visual and returned to 16.117V by May 19.36853 UT:

2013 May 14.72821 UT, 17.172V +/-0.017 (Gordon Myers, Hillsborough, CA);
15.24844, 16.623V +/-0.064 (Arto Oksanen, Muurame, Finland);
15.24926, 17.018V +/-0.113 (Oksanen);
15.25009, 16.733V +/-0.100 (Oksanen);
15.25091, 16.965V +/-0.094 (Oksanen);
15.25175, 16.944V +/-0.122 (Oksanen);
16.52780, 13.0 (Rod Stubbings, Tetoora Road, Vic, Australia);
17.72969, 13.971V +/-0.003 (Myers);
18.40935, 13.445V +/-0.086 (Kevin Hills, Hartford, Cheshire, England);
19.36770, 16.073V +/-0.020 (Oksanen);
19.36853, 16.117V +/-0.020 (Oksanen).
    
After DT Oct, the next target will be the WZ Sge-type cataclysmic variable GW Lib:

GW Lib   2013 May 30 10:30:11 through 15:40:30 UT

Giving DT Oct highest priority, please begin covering GW Lib now; close monitoring through May 31 is essential. GW Lib is V=16.5 at minimum and 8V at maximum.

Following GW Lib, the WZ Sge-type cataclysmic variable V1108 Her is scheduled for approximately 2013 June 3 UT. V1108 Her is 17.7V at minimum and 10.4V 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.

Coordinates (2000.0)
DT Oct                       R.A. 18 40 52.31   Dec. -83 43 10.0
GW Lib                      R.A. 15 19 55.34   Dec. -25 00 24.58
V1108 Her                 R.A. 18 39 26.21   Dec. +26 04 08.9

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 DT OCT, GW LIB, and V1108 HER, 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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