Thursday, July 28, 2005, Pratt Conference Room at 12:30 pm

Lightcurve Effects Due to Exomoons in Exoplanetary Transits

Dr. Gyula Szabo (University of Szeged, Hungary)

Observing the photometric transits is a widely applied tool for detecting exoplanets. The power of photometric detection is very likely to increase rapidly in the future, thanks to the planned space photometric campaigns. Their photometric accuracy is suspected to be few millimagnitudes.
Szabo, Szatmary & Diveki (2005) and Szabo et al (2005, before submission) examined weather an ``exomoon'' (i.e. a moon belonging to an exoplanet), moving around its planet can cause measurable timing effect of primary and secondary transits, or measurable lightcurve distortions which exceed few mmag.
We modeled physically real planets with moons which system orbits around a real star model. Our code calculates lightcurves for primary transits. The limb darkening and the inclination of both the exoplanetary and exolunar orbits are taken into account. The orbits are circular, the planet-moon eclipses are neglected. So as to exclude the short-time capture of the moon, the system has to fulfill Hill stability.
In my talk I'll address the following aspects:

Timing effects: transits somewhat prior or behind to time occurring due to the motion of the planet around the baricenter.
Semi-transit effects: when the exomoon alone is in transit, before or after the transit of the exoplanet; or contrary, the exoplanet is in transit but the exomoon is not.
Lightcurve ``modulation'': because of the limb darkening of the star, a very small variation in the transit lightcurve occurs depending on the position of the moon relatively to the planet.

The systems with known photometric transit have central stars of about the solar-size; therefore the maximal effect of the theoretical moons are rather tiny. However, these tiny effects would be detectable in the future, as these magnitudes fits to the planned photometric accuracy of the appropriate (mostly space-based) telescopes.