A Review of the Current Status of Follow-Up Techniques to Study Known Extrasolar Planets.pdf

a r X i v : a s t r o - p h / 0 3 1 2 2 5 2 v 1 1 0 D e c 2 0 0 3 IAU Symposium 219: Stars as Suns: Activity, Evolution, and Planets ASP Conference Series, Vol. , 2004 A. O. Benz A. K. Dupree, eds. A Review of the Current Status of Follow-Up Techniques to Study Known Extrasolar Planets David Charbonneau California Institute of Technology, MC 105-24 (Astronomy), 1200 E. California Blvd., Pasadena, CA 91125 USA; dc@caltech.edu Abstract. I present a review of observational efforts to study known ex- trasolar planets by methods that are complementary to the radial velocity technique. I describe the current state of attempts to detect and char- acterize such planets by astrometry, by reflected light, by thermal emis- sion, by transit photometry, by atmospheric transmission spectroscopy, by planet-induced chromospheric activity, and by long-wavelength radio emission. With a few exceptions, these efforts have yielded only up- per limits. Nonetheless, the diversity and vivacity of these pursuits has rapidly pushed many of these techniques into the realm where realistic models of the planets and their atmospheres can now be confronted. 1. Introduction Doppler surveys of nearby Sun-like stars continue to supply the bulk of informa- tion by which we are learning about the planets that orbit our stellar neighbors. The current state-of-the-art in radial velocity precision did not come easily: It is the result of years of dedicated effort by numerous groups to develop the optimal instrumental methods, prior to the announcement of the first success- ful detections. By analogy, dozens of research groups are now exploring novel techniques to follow-up and characterize these newly-detected planets. Many of these methods were considered completely unrealistic prior to discovery of the great diversity of planetary systems, when only our own Solar system served as a guide. Notably, several techniques have been fueled by the detection of gas giants that are either significantly mor