Research: Planets around active stars
The deformations of line profiles in spectra can tell a lot about the
activity and surface structure of a star. These variations of the line's
shape can be used to create Doppler Images, which show the spot
distribution on the star's surface, if appropriate data and necessary
information about the star (for example its exact rotation period) are
available. Additionally the rotation velocity of stars one wants to use
for Doppler Imaging has to be higher than approximately 25 km/s.
By nature radial velocity measurements of such fast rotating stars are especially difficult, because the error increases with the width of the line. Considering stellar activity, which causes asymmetric line profile deformations, it is even more problematic to get RV measurements with accuracies of a hundred m/s or less, which must be achieved for planet detections.
To increase the accuracy of RV measurements of heavily Doppler broadened spectra, the influences of stellar activity on the line profiles must be analyzed in detail. This enables us to distinguish between RV shifts due to line profile deformation and RV shifts due to stellar companions such as planets.
- Huber, K. F., Czesla, S., Wolter, U., Schmitt, J. H. M. M. (2010) Planetary eclipse mapping of CoRoT-2a. Evolution, differential rotation, and spot migration», A&A, Vol. 514, p. A39
- Reiners, A., Bean, J. L., Huber, K. F., Dreizler, S., Seifahrt, A., Czesla, S. (2010) Detecting Planets Around Very Low Mass Stars with the Radial Velocity Method», ApJ, Vol. 710, p. 432
- Huber, K. F., Czesla, S., Wolter, U., Schmitt, J. H. M. M. (2009) A planetary eclipse map of CoRoT-2a. Comprehensive lightcurve modeling combining rotational-modulation and transits», A&A, Vol. 508, p. 901
- Czesla, S., Huber, K. F., Wolter, U., Schröter, S., Schmitt, J. H. M. M. (2009) How stellar activity affects the size estimates of extrasolar planets», A&A, Vol. 505, p. 1277
- Wolter, U., Schmitt, J. H. M. M., Huber, K. F., Czesla, S., Müller, H. M., Guenther, E. W., Hatzes, A. P. (2009) Transit mapping of a starspot on CoRoT-2. Probing a stellar surface with planetary transits», A&A, Vol. 504, p. 561
- Huber, K. F., Wolter, U., Czesla, S., Schmitt, J. H. M. M., Esposito, M., Ilyin, I., González-Pérez, J. N. (2009) Long-term stability of spotted regions and the activity-induced Rossiter-McLaughlin effect on V889 Herculis. A synergy of photometry, radial velocity measurements, and Doppler imaging», A&A, Vol. 501, p. 715