91福利

Title: A Radial velocity search for low mass M dwarf planets

Abstract: Low mass planets orbiting the lowest mass stars are expected in significant numbers in close orbits of a few days to a few tens of days. To date, however, the nearby population of late M stars has not been targeted by precision radial velocity surveys. I will present radial velocity measurements for a sample of M5V - M9V from the Red-Optical Planet Survey, ROPS, that operates in the 0.65 - 1 micron regime. Radial velocities with r.m.s. precision down to 2.5 m/s over a week long time scale indicate sensitivities to planets with masses >= 1.5 M_Earth in the classical habitable zone can be achieved. In 9/15 of our targets, observations currently rule out the presence of planets with masses >= 10 M_Earth in close orbits.

Late M stars on average show significant rotation, and chromospheric activity is in fact found in a number of the ROPS targets. The implication that most M dwarfs are significantly spotted, and hence exhibit time varying line distortions, indicates that observations to detect orbiting planets need strategies to reliably mitigate against the effects of activity induced radial velocity variations. I will also present estimates of detection thresholds for spotted M stars and a new procedure for removing starspot noise.