CoRoT-1: observations of the exoplanet transits
Observed: 28 Dec 2008, 18, 21 Mar 2009
An example of an image:
The comparison stars are inside the yellow squares.
The ensemble aperture photometry is performed with the AstroMB program (version 2.8*), which fits the comparison stars with the Pogson's law, using their statistical uncertainties as weights. The magnitudes of the comparison stars are taken from the UCAC2 catalog.
Session 28 Dec 2008
The light curves:
Red: CoRoT-1, Blue: K1 shifted by 1.25 mag, Black: K2 shifted by 1.05 mag. The error bars are +/- the 1-sigma statistical uncertainties.
K1: average mag=12.209, average 1-sigma statistical uncertainty=6mmag, standard deviation=6mmag.
K2: 12.456mag, 7 and 9mmag respectively.
The sky quality during the session is assessed by computing the
extra losses. This is done by fitting the photometry zero point as a function
of the air mass by a line and by taking the difference (Gary (2007)):
Blue line: the fit. Green line: below the blue line by 0.1 mag (measurements below this line would be discarded). The measurements (red dots) are all well aligned along the blue line, therefore the sky quality is considered as good.
To assess the telescope stability, I measure the FWHM and check its
Sessions 18 and 21 March 2009
All the measurements are HERE.
The resulting phase plot:
The measurements may be smoothed by averaging them by bins of 20mn, and
for each bin the standard deviation is computed (using the statistical
uncertainties as weights):
The average standard deviation is 12mmag.
From a screen copy with BinaryMaker3:
The synthetic light curve of BinaryMaker3 and the smoothed
The observed transit may be slightly deeper than the synthetic one.
Barge P., Baglin A., Auvergne M. et al (2008) A&A 482 L17.
Bilir S., Ak S., Karaali S., Cabrera-Lavers A., Chonis T.S., Gaskell C.M. (2007) MNRAS and arXiv:astro-ph/0711.4356v1.
Gary B. (2007) Exoplanet observing for amateurs Reductionist Publications. (May be downloaded from http://brucegary.net/book_EOA/x.htm).
Mamajek E.E., Meyer M.R., Liebert J. (2002) AJ 124 1670 Appendix C; Erratum (2006) AJ 131 2360.
I also observed transits of WASP-2, which is 2 mag brighter than CoRoT-1, but the quality of the data is not too good.
Modelling with BinaryMaker3.
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