Presentations at the AAS Meeting - Washington, DC

January 2010

SPI or Spin-up? An UV Investigation of Activity on Exoplanet Host Stars

Evgenya Shkolnik1

1DTM, Carnegie Institution of Washington,

Talk on Wednesday, Jan 06, 2010, 10:00 AM -10:10 AM

I study the effects of tidal and magnetic star-planet interactions (SPI) on the stellar activity of the host stars using the near-UV and far-UV photometry of the GALEX All-sky Imaging Survey. I compare samples of stars with close-in planets (a < 0.15 AU) to those with far-out planets (a > 1.5 AU) and show that the former group has on average several times the FUV and NUV luminosity of the latter sample. This is consistent with the X-ray results of Kashyap et al. (2008), who speculate that this may be due to the magnetic influence on the star by its innermost planet, as previously observed in several individual hot Jupiter systems. My study suggests that increased stellar rotation rate due to the tidal interaction with the planet plays the dominant role in increasing the global stellar activity level. For the stars with close-in planets, the FUV and NUV fluxes are anti-correlated with the stellar synchronization time scales but are not correlated for stars with planets at larger orbital distances. Even though the stars with close-in planets are not fully synchronized (full synchronization in most cases will take longer than the age of the Universe), they have already undergone some increase in rotation rate. This result also suggests that the competing force of magnetic drag slowing down the stars is losing out to tidal spin-up in these systems.

Exoplanet Detection Combining Astrometric and Radial Velocity Measurements. Application to VB10b

Guillem Anglada-Escudé1, E. Shkolnik1, A. Weinberger1, I. Thompson2, D. Osip3

1DTM, Carnegie Institution of Washington, 2Carnegie Obs., 3Las Campanas Obs., Chile.

Talk on Tuesday, Jan 05, 2010, 3:00 PM - 3:10 PM

Ground based astrometry hasn't been very successful in detecting extrasolar planets. The reasons for that is the relatively long time baselines required, instrumental stability requirements and calibration related issues. In addition to that, the number of free parameters is large compared to other methods (such as radial velocities) and additional information is often required to constrain the true nature of the candidate signals. An example is the recently announced astrometric detection of a planet around the low mass star VB10, where a careful reanalysis of the data with existing Doppler measurements casts some doubts on the true nature of the announced low mass companion. Follow-up observations on this object (both astrometric and spectroscopic) have been obtained. We present the results of this campaign and a detailed analysis of the allowed orbital solutions which confirm/rule out the presence of this candidate.

The Gemini NICI Planet-Finding Campaign

Michael C. Liu1, Z. Wahhaj1, B. Biller1, M. Chun1, L. Close2, C. Ftaclas1, M. Hartung3, T. Hayward3, E. Nielsen2, D. Toomey4, E. Shkolnik5, I. Reid6, NICI Planet-Finding Campaign Team

1Univ. of Hawaii, 2Univ of Arizona, 3Gemini Observatory, Chile, 4Mauna Kea Infrared, 5Carnegie/DTM, 6STScI

Poster Session: Wednesday, Jan 06, 2010, 9:20 AM - 6:30 PM.

Our team is currently carrying out a major two-year, 50-night observing program to directly image and characterize young (<~1 Gyr) extrasolar planets using the Near-Infrared Coronagraphic Imager (NICI) on the Gemini-South 8.1-meter telescope. NICI is the first instrument on a large telescope designed from the start for high-contrast imaging, comprising a high-performance adaptive optics (AO) system with a simultaneous dual-channel coronagraphic imager. In combination with state-of-the-art AO observing and data analysis methods, NICI currently achieves better contrast than any previous ground-based or space-based instrument at separations inside of ~2 arcseconds. The Campaign Team has also carried out significant preparatory efforts to identify previously unrecognized young stars as targets and to develop a rigorous quantitative methodology for constructing the observing strategy. The Planet-Finding Campaign began in December 2008 and is in full operation, with deep imaging of several dozen stars already obtained. We describe the Campaign's goals, design, target selection, on-sky performance to date, and early science results. The NICI Planet-Finding Campaign represents the largest and most sensitive imaging survey to date for massive (~1 Mjup) planets around other stars.