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Special Notice #357: BD Pav next HST COS target followed by QZ Ser

June 7, 2013: Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471) and AAVSO Special Notice #356 (http://www.aavso.org/aavso-special-notice-356), HST/COS is scheduled to observe the eclipsing dwarf nova BD Pav:

BD Pav 2013 June 14 04:40:42 through 09:46:09 UT

The HST team will be making a final decision early on June 13 about observing BD Pav based substantially on your observations, so they are essential.
 
Close monitoring of BD Pav through June 15 is requested. BD Pav has brief oubursts to about 13V, and brighter, longer outbursts to 12.4V - SU UMa-like. It will be essential to know the brightness of BD Pav at all times in order to protect the HST equipment.

Dr. Gaensicke adds, "We expect a fair bit of variability during quiescence due to flickering and ellipsoidal modulation of the companion. Hence, if you can observe this southern star, please try to get a few measurements per night so that it will be possible to determine both the mean brightness level and the amplitude of the short-term variability."
    
After BD Pav, the next target will be the SU UMa-type dwarf nova QZ Ser:

QZ Ser  2013 June 21 02:29:47 through 09:14:45 UT

Giving BD Pav highest priority, please also monitor QZ Ser; close monitoring at least through June 22 is essential. QZ Ser is 17.9V at minimum and 12.7V or brighter at maximum. QZ Ser had a  superoutburst in March 2013, when it reached magnitude 12.1V/11.7visual, and does not have normal outbursts very often, so it is not likely to go into outburst before or during the HST observation window, but with CVs it is never wise to assume! After June 14, it will be essential to know the brightness of QZ Ser at all times.

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)
BD Pav                R.A. 18 43 11.919  Dec. -57 30 44.85
QZ Ser                R.A. 15 56 54.47   Dec. +21 07 19.0

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 BD PAV and QZ SER, 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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