AAVSO Alert Notice 359: Request to monitor SDSS074545 for HST Observations

Dr. Paula Szkody (University of Washington) has requested our help 
in monitoring the cataclysmic variable SDSS074545 
(SDSS J074531.92+453829.5) for upcoming Hubble Space Telescope 
observations. The HST observations are scheduled to be made during 
the week of 2007 October 29 -- November 03 UT.  Dr. Szkody requests
monitoring of this object during the two weeks prior to the 
observing window, and intensive monitoring during the 24-48 hour 
period during which observations will be made. An AAVSO Special 
Notice will be issued when HST ground controllers inform us the 
observing window is officially open.

SDSS074545 (0738+45) is at R.A. 07:45:31.92 , Dec +45:38:29.5 (J2000)

SDSS074545 is a cataclysmic variable not previously seen in outburst,
and is being observed as part of a larger study of pulsating white 
dwarf primaries in cataclysmic variables. In particular, Szkody and 
collaborators are investigating the effects that higher temperatures 
and larger rotation velocities caused by accretion have on the 
pulsation behavior.

This object is very faint at quiescence, with V=19.1.  AAVSO
observations are requested to ensure that the object is indeed faint 
when observed with HST, as it could damage the instrument if it were 
to go into outburst. AAVSO observations will be used to make a 
"go"/"no go" decision when the observing window opens, and will also
be used in the analysis of the resulting data.

Observers are asked to monitor SDSS074545 nightly beginning 
immediately (2007 October 19 UT). Visual observers please observe as
normal, and report any "fainter than" estimates using the faintest 
comparison star magnitude you can reach if unable to detect 
SDSS074545 itself. CCD observers are asked to use filters during 
observations if available; V filter is preferred, but B,Rc, and Ic 
may also be used. Detection of the variable itself is not required 
unless you can reach V=19 in reasonable time, but please use 
sufficient exposure to detect at least the V=15.8 comparison star 
(AUID 000-BCY-392; RA 07:45:35.45 Dec +45:38:47.6) with a S/N of 10
and report the observation as a "fainter-than" measure.

Beginning 2007 October 29 UT, please observe this object as often as
possible for the duration of the week using the observing procedure
outlined above, and submit data as soon as is possible via WebObs.
In the event of an outburst, please contact the AAVSO immediately.

A charts for SDSS074545 are available at this URL:

http://www.aavso.org/observing/charts/vsp/index.html?pickname=0738%2B45

For more information on this campaign, visit the following URL:
http://www.aavso.org/news/sdss074545.shtml

This campaign is being organized at AAVSO HQ by Dr. Matthew Templeton.

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