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Special Notice #356: V1108 Her obs urgent TONIGHT and new date for BD Pav

June 4, 2013: Further to AAVSO Alert Notice 471 ( and AAVSO Special Notice #355 (, HST/COS is scheduled to observe the WZ Sge-type cataclysmic variable V1108 Her:

V1108 Her  2013 June 6 09:32:19 through 13:42:14 UT

The HST team will be making a final decision early on June 5 about observing V1108 Her based substantially on your observations, so they are ESSENTIAL.

Close monitoring of V1108 Her through June 7 is requested. V1108 Her is 17.7V at minimum and 10.4V at maximum.
After V1108 Her, the next target will be the dwarf nova BD Pav:

BD Pav   2013 Jun 14     time to be announced

Giving V1108 Her highest priority, please also monitor BD Pav; close monitoring at least through June 15 is essential. BD Pav is 15.4V at minimum and 12.4V at maximum. BD Pav has brief oubursts to about 13V, and brighter, longer outbursts to 12.4V - SU UMa-like. After June 6, it will be essential to know the brightness of BD Pav at all times in order to protect the HST equipment.

V1108 Her is 1" from a low-mass red visual companion that dominates in the red. Since it is very difficult to properly resolve the two objects, Dr. Gaensicke requests that observers report the combined magnitude (a correction for the companion contribution will be made afterwards by the astronomers).

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)
V1108 Her                 R.A. 18 39 26.21   Dec. +26 04 08.9
BD Pav                      R.A. 18 43 11.919  Dec. -57 30 44.85

Charts may be created using the AAVSO Variable Star Plotter (

Please report observations as soon as possible to the AAVSO International Database using the names V1108 HER and BD PAV, 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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