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Special Notice #209: Nightly monitoring of TW Hya in support of HST observations

May 17, 2010: Dr. Michael Sitko (U. Cincinnati) requests observations of the young stellar object TW Hya in support of upcoming Hubble Space Telescope observations. TW Hya is believed to be a T Tauri star that varies between magnitudes 10.5 and 12.2. TW Hya will be observed with the HST STIS instrument as part of a larger program to study the properties of potentially planet-forming disks around young stars. The star will be observed in the ultraviolet to search for time-variability in the gas in the inner accretion disk. Ground-based photometry will provide valuable information on the photometric activity of TW Hya at the time of the Hubble observations.
 
AAVSO observers are asked to monitor TW Hya beginning immediately (2010 May 17, JD 2455334) and continuing through 2010 June 4 (JD 2455352). Nightly observations are requested. Instrumental observers are asked to acquire filtered observations in the B,V,Rc, and Ic bands if possible.
 
TW Hya is a southern source, ideal for southern observers. A sequence for this star has been added to VSD. Both visual and CCD observers are encouraged to participate. Since the star is relatively bright, CCD observers should be able to obtain reasonable signal to noise in a short amount of time. CCD observers are encouraged to transform their data to a standard system prior to submission to the AAVSO.
 
TW Hya is located at the following (J2000) coordinates:
RA: 11 01 51.91 , Dec: -34 42 17.0
 
Charts for TW Hya may be plotted using AAVSO VSP (http:www.aavso.org/vsp). Note that the "124" comparison star does not appear on plotted charts, but will appear on DSS charts. Please use DSS charts for the time being.
 
Please submit all observations to the AAVSO using the name "TW HYA".
 
This AAVSO Special Notice was prepared by M. Templeton.
 
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