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

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

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

RV measurements P. Weise – RV survey of stars with circumstellar disks Our survey consists of 580 stars 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 RV measurements are obtained by crosscorrelating stellar spectra with theoretical templates The crosscorrelation profile gives RV and vsini of the star The crosscorrelation profile gives RV and vsini of the star Data reduction tools to crosscorrelate spectra of very young stars do not exists Data reduction tools to crosscorrelate spectra of very young stars do not exists  We are currently developing a new tool

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

Stellar activity Stellar spectral line shapes are affected by 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

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

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

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

Observing strategy More than 1 period has to be well sampled 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 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

Analysis strategy Analyse RV and Line Shape Analyse RV and Line Shape If Bisector does not correlate with RV: 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 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

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

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

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

First results from our survey Brown Dwarf candidates Brown Dwarf candidates P. Weise – RV survey of stars with circumstellar disks Age: 5Myr M * : 2 M ʘ P: 38 d m 2 sini: 31 M jup Age: 3-5Myr M * : 2.5 M ʘ P: 39 d m 2 sini: 41 M jup

First results from our survey Planetary candidate Planetary candidate P. Weise – RV survey of stars with circumstellar disks Age: 10Myr M * : 1-2 M ʘ P: 34 d m 2 sini: 5-9 M jup Age: 75Myr M * : 0.9 M ʘ P: 92.7 d m 2 sini: 4 M jup

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