Skip to main content

Web Publications

AAVSO Alert Notice 393: Monitoring for a planetary transit of HD 80606 AAVSO HOME > publications > alert notice

AAVSO Alert Notice 393

Monitoring for a planetary transit of HD 80606
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 ,

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

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

Crawford gives links to two additional papers on CCD coefficients:

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

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.


Information on submitting observations to the AAVSO may be found at:


An Alert Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL:

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484