1 / 18

Radial-velocity planet-search survey of stars with circumstellar disks

Radial-velocity planet-search survey of stars with circumstellar disks. Patrick Weise Johny Setiawan, Ralf Launhardt, André Müller, Thomas Henning Max-Planck-Institute for Astronomy, Heidelberg. Overview. Why are young planets important? Are precise RV measurements possible?

larue
Download Presentation

Radial-velocity planet-search survey of stars with circumstellar disks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Radial-velocity planet-search survey of stars with circumstellar disks Patrick Weise Johny Setiawan, Ralf Launhardt, André Müller, Thomas Henning Max-Planck-Institute for Astronomy, Heidelberg

  2. Overview • Why are young planets important? • Are precise RV measurements possible? • MACS - A new Crosscorrelation tool • Stellar activity and its effects on RV measurements • First results from our survey P. Weise – RV survey of stars with circumstellar disks

  3. Planets around young stars • What processes affect the formation and evolution of planets? • When and where do planets form? • How do planets form? Important questions: • Can planets be detected in circumstellar disks? • How long need planets to be formed? P. Weise – RV survey of stars with circumstellar disks

  4. Suitable targets? • Are young stars suitable for precise RV measurements? • Young (accreating) stars with circumstellar disks are usually slow rotators and precise RV is possible Accuracy for BD comp. Accuracy for planetary comp. FEROS long-term accuracy P. Weise – RV survey of stars with circumstellar disks

  5. RV measurements • Our survey consists of 580 stars • Selected by youthness (<300Myr), dwarf stars, single stars • RV measurements are obtained by crosscorrelating stellar spectra with theoretical templates • The crosscorrelation profile gives RV and vsini of the star • Data reduction tools to crosscorrelate spectra of very young stars do not exists • We are currently developing a new tool P. Weise – RV survey of stars with circumstellar disks

  6. Crosscorrelation tool • MACS is a new tool for crosscorrelating stellar spectra with theoretical templates P. Weise – RV survey of stars with circumstellar disks

  7. Stellar activity • Stellar spectral line shapes are affected by • Cold and hot spots on the surface • Granulation • Non-radial pulsations • Stellar winds P. Weise – RV survey of stars with circumstellar disks

  8. Effect on RV • Spots and stellar winds alter spectral line shape • Measurable by line bisector variation Müller, 2008 • Line bisector varies with RV Huerta, 2007 P. Weise – RV survey of stars with circumstellar disks

  9. Photometry • Photometric data is needed to check for short-periodic variation due to stellar spots and to identify stellar rotation period • Signals due to stellar spots are quasi-periodic and short-lived (for young stars) Huerta, 2007 P. Weise – RV survey of stars with circumstellar disks

  10. NIR spectroscopy • Amplitude of RV signal decreases with wavelength when signal is due to spots • Observationally not yet proven. First results are inconclusive • This is an effect of lowered contrast between spot and photosphere P. Weise – RV survey of stars with circumstellar disks

  11. Observing strategy • More than 1 period has to be well sampled • To verify that amplitude and period of the signal are stable over time • Stellar spots are short-lived and amplitude changes • Several exposures in one night needed • To identify short-period stellar activity jitter • Rotational period from activity indicators (for young stars ~2-4 days) P. Weise – RV survey of stars with circumstellar disks

  12. Analysis strategy • Analyse RV and Line Shape • If Bisector does not correlate with RV: • Check other activity indicators • Hα, CaII, NaI, HeI, Line depth ratio FeI/VI, Veiling, photometric data • Check them for periodicity • If stellar activity indicators show no periodicity or other than RV measurements • Obtain NIR spectroscopy data P. Weise – RV survey of stars with circumstellar disks

  13. Our Survey • Targetlist of 580 young (<600 Myr) stars • 208 have been observed with FEROS and analysed for stellar parameters • 58 stars have multi-epoch data • 27 stars show signs of circumstellar disks and 8 are still accreating P. Weise – RV survey of stars with circumstellar disks

  14. First results from our survey • 208 stars have been observed 24 are RV stable 184 show RV variation 133 have vsini<30km/s 34 are SB 58 with more data 33 carefully analysed Signal due to stellar activity 8 Planetary comp. 2 BD comp. 4 P. Weise – RV survey of stars with circumstellar disks

  15. First results from our survey • RV variation due to stellar spots K0V star vsini=26 km/s Age=5 Myr P. Weise – RV survey of stars with circumstellar disks

  16. First results from our survey • Brown Dwarf candidates Age: 3-5Myr M*: 2.5 Mʘ P: 39 d m2sini: 41 Mjup Age: 5Myr M*: 2 Mʘ P: 38 d m2sini: 31 Mjup P. Weise – RV survey of stars with circumstellar disks

  17. First results from our survey • Planetary candidate Age: 10Myr M*: 1-2 Mʘ P: 34 d m2sini: 5-9 Mjup Age: 75Myr M*: 0.9 Mʘ P: 92.7 d m2sini: 4 Mjup P. Weise – RV survey of stars with circumstellar disks

  18. Summary • RV surveys of young stars are possible and very important for planet formation and early evolution • Stellar activity indicators have to be analysed very carefully • To improve data reduction for young stars, we are currently developing a new crosscorrelation tool • Our survey has just started to find potential planetary host stars with age  10 Myr • NIR spectroscopy has to be obtained to verify planetary companions P. Weise – RV survey of stars with circumstellar disks

More Related