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Alert Notice 393: Monitoring for a planetary transit of HD 80606

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February 3, 2009: Dr. Greg Laughlin (Lick Observatory) requests intensive time-series photometry of the possible transiting extrasolar planetary system HD 80606. This system, recently in the news due to the extreme temperatures to be found on the planet, is predicted to reach conjunction on or around HJD 2454876.5 (2009 Feb 14.0 UT), and there is a low but significant probability (<15%) that the system is eclipsing. If it eclipses, the duration of the eclipse may be as long as 17 hours. Observers are requested to perform high-S/N, filtered photometry of this bright star during a window beginning 48 hours before the predicted eclipse and ending 48 hours after.

Due to the long duration of the eclipse, it is unlikely that a single observer will be able to follow the transit from ingress through egress. Therefore, in order to model the eclipse profile, the data of many observers will need to be combined. Because the transit is expected to have low amplitude (on the order of 10 mmag), high-precision photometry of HD 80606 is required, and users are *strongly encouraged* to fully calibrate and transform their data and perform an extinction correction prior to submission. Doing so will make the process of combining data from different observers far easier. The following color data for HD 80606 should be used when performing transformations to the standard system: V=9.127 , (B-V)=+0.786 , (V-Rc)=+0.431 , (Rc-Ic)=+0.356 , (V-Ic)=+0.784.

If you do not transform your data, please make sure you include photometry of the uneclipsed star either prior to ingress or after egress, to enable us to detect the eclipse. Without calibration or a pre- or post-eclipse measure, we cannot compute an offset for your photometry.

For more information on computing transformation coefficients for your telescope, please read the following aavso-photometry post by Tim Crawford from March 2008:

[broken link]

Crawford gives links to two additional papers on CCD coefficients:

which is an instruction manual for computing them, prepared by Lou Cohen, and

[on that page click on "The M67 Unfiltered Photometry Experiment"] which is a paper on the differences between transformed and untransformed data by Arne Henden. We note that by computing your transformation coefficients, you can use them both for these data as well as for all future data you submit to the AAVSO on any star taken with the same telescope, CCD, and filter set.

Because HD 80606 is bright (V = 9.13), care must be taken when performing photometry. Please see

which is a CCD Views article on bright star photometry for suggestions on how best to perform accurate photometry.

HD 80606 is located at the following (J2000) coordinates:

RA: 09 22 37.5679 , Dec: +50 36 13.397

Charts for HD 80606 may be plotted using VSX:

Note that HD 80606 is a close double, and that the star of interest is the western member of the pair.

Please submit all data to the AAVSO using the name HD 80606 (AUID 000-BCZ-783).

This AAVSO Alert Notice was prepared by Dr. Matthew Templeton.



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