Astrometric Search for Exoplanets in Stellar Multiple Systems

The main principle of our astrometric search program is to measure the separation of nearby stellar multiple systems (e.g. binaries) over the time very precisely. An unseen companion orbiting one of the stellar components would introduce a reflex motion of its host star (also called "wobble") on a much shorter time scale than the typically orbital period of a visual binary.

A Jupiter mass planet at a distance of 10 parsec orbiting a solar like star within five years would cause an astrometric signal of about 0.6 milli arcsec. In contrast to the radial velocity technique and transit observations, astrometry is much more sensitive for planets with larger orbital radii, thus astrometric observations will typically take several years to detect an astrometric signal.

Our astrometric search program is still ongoing and as a first result, we detected a higher mass astrometric companion in the previous known stellar binary HD 19994, where a radial velocity planet candidate was found around the primary HD 19994 A by Mayor et al. in 2004. The existence of the new astrometric companion, which orbits the secondary of the HD 19994 system, is confirmed by speckle interferometry as well as by follow-up radial velocity measurements. The mass of the new C component is about 0.335 solar masses, while the mass of HD 19994 B is revised to about 0.55 solar masses (Roell et al., 2011, EAS, 45, 429).

optimiert zur Anzeige auf Mozilla Firefox | Impressum