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AAVSO Alert Notice 513 March 18, 2015
Request for observations of GW Lib in support of HSTobservations
Dr. Paula Szkody, University of Washington, has requestedour help in monitoring the cataclysmic variable GW Lib for upcoming HubbleSpace Telescope observations, scheduled to be made during the window 2015 April22-25 UT. Dr. Szkody also observed this object with HST in March 2011 and March2010 (see AAVSO Alert Notices 433 and 417, respectively).
AAVSO observations are needed to ensure that the objectis NOT in outburst when observed with HST. AAVSO observations made April 21-24 will be used to make a go/no go decision, and willalso be used in the analysis of the resulting data. In mid-April the schedulerswill give Dr. Szkody the exact date of the HST observations, and an AAVSOSpecial Notice will be issued.
Dr. Szkody requests nightly monitoring of this objectbeginning now, intensive monitoring April 21-25, and nightly observationsthrough May 2.
Coordinates: RA: 15 19 55.45 , Dec: -25 00 25.30(J2000.0)
GW Lib is a cataclysmic variable that is part of a largerstudy of pulsating white dwarf primaries in cataclysmic variables. Inparticular, Szkody and collaborators are investigating the effects that highertemperatures and larger rotation velocities caused by accretion have on thepulsation behavior. In these HST observations, they want to measure thetemperature of the white dwarf at minimum.
GW Lib is faint at quiescence, magnitude ~16.8visual/unfiltered. It is also an observing challenge because of its -25odeclination and because, at RA 15 hr, it is a late-night object. If visualobservers are unable to detect GW Lib, please report any"fainter-than" estimates using the magnitude of the faintestcomparison star magnitude seen. CCD observers are asked to use filters duringobservations if available; V filter is preferred, but B, Rc, and Ic may also beused. Detection of the variable itself is not required unless you can reachV=16.8 in reasonable time, but please use sufficient exposure to detect at leastthe V=143 comparison star (RA 15:19:39.54 Dec. -25:00:31.8)or V=147 (RA 15:20:01.73 Dec. -24:58:37.7) with a S/N of 10and report the observation as a "fainter-than" observation.
Beginning now, please observe this object as often aspossible according to the schedule and using the observing procedure outlinedabove, and submit data as soon as possible to the AAVSO International Databaseusing the name GW LIB. During the nights of April 20-21, 21-22, 22-23, and23-24 prompt submission of your observations will be critical. In the event ofan outburst, please contact the AAVSO immediately.
Thank you for your observing efforts and valuableobservations!
This AAVSO Alert Notice was prepared by Elizabeth O.Waagen.
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發表於 2015-3-19 08:42:09