Aarhus Universitets segl

SAC seminar - Trifon Trifonov: Testing the planetary hypothesis around evolved K giants. Planetary dynamics and high precision optical and near-IR spectroscopy

Oplysninger om arrangementet

Tidspunkt

Torsdag 6. februar 2014,  kl. 15:15 - 16:00

Sted

1520-516

Location: 1520-516

Time: 3.15 p.m.

Abstract:

The number of planets and brown dwarfs detected around K giants is already more than 50 and is constantly growing. Some of these discoveries were part of our 373 G an K giant sample observed at Lick observatory since 1999. Are all these planets indeed real? In particular, pulsations (of unknown nature) or rotational modulation of surface features such as spots could not be excluded.Thus, an independent confirmation of this interpretation of the radial velocity (RV) data is urgently needed.

In my work I have applied two quantitative tests that can finally close the case. First, I have obtained a precise RVs from the near-IR using the ESO's CRIRES spectrograph for a sample of 20 K giants with planetary candidates from Lick. Intrinsic stellar RV variations will lead to differences in RV phase and amplitude between the optical and near-IR, while, in case of a planet, both data sets are expected to be consistent. Second, for the systems that clearly show signatures of harbouring a multi planetary systems I have explored the dynamical properties of these systems by preforming deep and conclusive stability test using Mercury N-body integrator. Both methods turned out to be successful. The near-IR
velocity precision is in the order of 30?40 m/s, enough to confirm the RV phase and amplitude, and thus, the planetary nature of most of our candidates. The long term stability test shows that some systems have stable best fit, while the rest have broad and confident long term-stable regions in orbital parameter space within 1 or 2 sigma away from the best fit.