Exoplanets moving across the stellar disk

Brief Overview
HD 209458 lightcurve
Target Fields
Papers

Brief Overview

The first exoplanet was found in 1995 by Michel Mayor from the Geneva Observatory. The planet is a Jupiter size planet in a very tight orbit around the star 51 Peg. The short period was quite a surprise since planets were not expected to survive in orbits that close to a star. Later even close planets have been detected with periods between 1 and 2 days. When the orbital period is just a few days the chance of an occultation is around 10 percent, so several groups starting to look for small drops in the lightcurve of the parent stars. True enough, one of the exoplanet stars showed evidence of a planet transiting the stellar disk. Now, due to large efforts by several teams, quite a number of systems have been found (The count now stands at 52, Sep. 15, 2008). The transits are only observable occasionally and it is necessary first to figure out, whether the targets are observable during the allocated observing time , and next to check, whether an eclipse takes place during the one or more of the nights. If none of the two examples given below are observable in a given period, try to consult the Exoplanet Encyclopedia. Here you can find many transiting planets. Actually the count is so high now, that there is a fair chance to find a transiting system on any night.

A very productive project among the search programmes for transiting planets is SuperWASP, which is also a good source for targets. The list includes (10.11.2008) 15 targets.

This project aims at observing one of the eclipses in different filters to try to measure colour differences.

A major part of the preparations is actually to calculate times of transits and compare with the allocated observing nights to see if a transit do occur. Due to the large number of systems this needs to be done in a systematic way. You may search for tables of transits that some people produce from time to time.

The first transiting planet was reported by Brown et al. occulting the star HD 209458. This is a solar type star of spectral type G0V. The orbital period is short, P=3.52474541 +- 0.00000025, and mid transit time in HJD is T=2 452 854.825415 +- 0.000060.

The basic parameters for HD 209458 are:
Ra(J2000) = 22 03 10.8
Dec(J2000) = 18 53 04
V = 7.65
B-V =

This was the first planet found by looking for transits only without knowing in advance from Doppler measurements, that a planet was present. The period is short, P=3.030065 +- 0.000008. Mid transit is T=2 453 186.8060 +- 0.002. The star has spectral class K0V and is therefore smaller and cooler than the Sun.

The basic parameters for TrES-1 are:
Ra(J2000) = 19 04 09.8
Dec(J2000) = 36 37 57
V = 11.79
B-V =

This is a recently discovered system reported by Bouchy et al. 2005. It has a deeper eclipse than the two other systems of appr. 3%. Mid transit is T=2 453 629.389 +- 0.0005 and the period is P=2.219+-0.0005 days. The star is a high proper-motion star with spectral class G5.

Basic parameters are:
RA(J2000) = 20 00 43.7
Dec(J2000) = 22 42 39.1
V = 7.5
B-V = 1.0

Lightcurve for HD 209458

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The lightcurve from the Exoplanet Encyclopedia.


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Exoplanet Fields

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Papers on transiting planets

Alonso et al. 2004, ApJL 613, L153 (pdf file 1.5M) Discovery paper for TrES-1
Charbonneaud et al. 1999, ApJ, 529, 45 (pdf file 3.5M) HD 209458 planet.
Bouchy et al. 2005, Astro-ph/0510119


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