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

OverviewOverview

Why are young planets important?Why are young planets important?

Are precise RV measurements possible?Are precise RV measurements possible?

MACS - A new Crosscorrelation toolMACS - A new Crosscorrelation tool

Stellar activity and its effects on RV Stellar activity and its effects on RV

measurementsmeasurements

First results from our surveyFirst results from our survey

P. Weise – RV survey of stars with circumstellar disks

Planets around young starsPlanets around young stars

What processes affect the formation and What processes affect the formation and evolution of planets?evolution of planets?

When and where do planets form?When and where do planets form? How do planets form?How do planets form?


Important questions: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?Suitable targets?

Young (accreating) stars with circumstellar disks Young (accreating) stars with circumstellar disks are usually slow rotators and precise RV is possibleare usually slow rotators and precise RV is possible


Are young stars suitable for Are young stars suitable for precise RV measurements?precise RV measurements?

Accuracy for BD comp.

Accuracy for planetary comp.FEROS long-term accuracy

RV measurementsRV measurements


Our survey consists of 580 starsOur survey consists of 580 stars

Selected by youthness (<300Myr), dwarf Selected by youthness (<300Myr), dwarf stars, single starsstars, single stars

RV measurements are obtained by RV measurements are obtained by crosscorrelating stellar spectra with theoretical crosscorrelating stellar spectra with theoretical templatestemplates

The crosscorrelation profile gives RV and vsini The crosscorrelation profile gives RV and vsini of the starof the star

Data reduction tools to crosscorrelate spectra of Data reduction tools to crosscorrelate spectra of very young stars do not existsvery young stars do not exists

We are currently developing a new toolWe are currently developing a new tool

Crosscorrelation toolCrosscorrelation tool

MACS is a new tool for crosscorrelating stellar MACS is a new tool for crosscorrelating stellar spectra with theoretical templatesspectra with theoretical templates


Stellar activityStellar activity

Stellar spectral line shapes are affected byStellar spectral line shapes are affected by

Cold and hot spots on the surfaceCold and hot spots on the surface GranulationGranulation Non-radial pulsationsNon-radial pulsations Stellar windsStellar winds


Effect on RVEffect on RV

Spots and stellar winds alter spectral line shapeSpots and stellar winds alter spectral line shape


Measurable by line Measurable by line bisector variationbisector variation

Line bisector varies Line bisector varies with RVwith RV

Huerta, 2007Huerta, 2007

Müller, 2008Müller, 2008

PhotometryPhotometry

Photometric data is needed to check for short-periodic Photometric data is needed to check for short-periodic variation due to stellar spots and to identify stellar variation due to stellar spots and to identify stellar rotation periodrotation period


Huerta, 2007Huerta, 2007

Signals due to stellar spots are quasi-periodic and Signals due to stellar spots are quasi-periodic and short-lived (for young stars)short-lived (for young stars)

NIR spectroscopyNIR spectroscopy


This is an effect of lowered contrast between spot This is an effect of lowered contrast between spot and photosphereand photosphere

Amplitude of RV signal decreases with Amplitude of RV signal decreases with wavelength when signal is due to spotswavelength when signal is due to spots

Observationally not Observationally not yet proven. First yet proven. First results are results are inconclusiveinconclusive

Observing strategyObserving strategy

More than 1 period has to be well sampledMore than 1 period has to be well sampled To verify that amplitude and period of the To verify that amplitude and period of the

signal are stable over timesignal are stable over time Stellar spots are short-lived and amplitude Stellar spots are short-lived and amplitude

changeschanges Several exposures in one night neededSeveral exposures in one night needed

To identify short-period stellar activity To identify short-period stellar activity jitterjitter

Rotational period from activity indicators Rotational period from activity indicators (for young stars (for young stars ~~2-4 days)2-4 days)


Analysis strategyAnalysis strategy

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

Check other activity indicatorsCheck other activity indicators HHαα, CaII, NaI, HeI, Line depth ratio , CaII, NaI, HeI, Line depth ratio

FeI/VI, Veiling, photometric dataFeI/VI, Veiling, photometric data Check them for periodicityCheck them for periodicity

If stellar activity indicators show no periodicity If stellar activity indicators show no periodicity or other than RV measurementsor other than RV measurements

Obtain NIR spectroscopy dataObtain NIR spectroscopy data


Our SurveyOur Survey

Targetlist of 580 young (<600 Myr) starsTargetlist of 580 young (<600 Myr) stars 208 have been observed with FEROS and 208 have been observed with FEROS and

analysed for stellar parametersanalysed for stellar parameters 58 stars have multi-epoch data58 stars have multi-epoch data 27 stars show signs of 27 stars show signs of circumstellar disks and 8circumstellar disks and 8

are still accreatingare still accreating




208 stars have been observed208 stars have been observed

24 are RV stable24 are RV stable 184 show RV variation184 show RV variation

34 are SB34 are SB133 have vsini<30km/s133 have vsini<30km/s

Signal due to Signal due to

stellar activitystellar activity

88

Planetary comp.Planetary comp.

22

BD comp.BD comp.

44

58 with more data58 with more data

33 carefully analysed33 carefully analysed


RV variation due to stellar spotsRV variation due to stellar spots


K0V star K0V star vvsinsinii=26 km/s Age=5 Myr=26 km/s Age=5 Myr


Brown Dwarf candidatesBrown Dwarf candidates


Age: 5Myr MAge: 5Myr M**: 2 M: 2 Mʘʘ

P: 38 d mP: 38 d m22sini: 31 Msini: 31 Mjupjup

Age: 3-5Myr MAge: 3-5Myr M**: 2.5 M: 2.5 Mʘʘ

P: 39 d mP: 39 d m22sini: 41 Msini: 41 Mjupjup


Planetary candidatePlanetary candidate


Age: 10Myr MAge: 10Myr M**: 1-2 M: 1-2 Mʘʘ

P: 34 d mP: 34 d m22sini: 5-9 Msini: 5-9 Mjupjup

Age: 75Myr MAge: 75Myr M**: 0.9 M: 0.9 Mʘʘ

P: 92.7 d mP: 92.7 d m22sini: 4 Msini: 4 Mjupjup

SummarySummary

RV surveys of young stars are possible and very RV surveys of young stars are possible and very important for planet formation and early evolutionimportant for planet formation and early evolution

Stellar activity indicators have to be analysed very Stellar activity indicators have to be analysed very carefully carefully

To improve data reduction for young stars, we are To improve data reduction for young stars, we are currently developing a new crosscorrelation toolcurrently developing a new crosscorrelation tool

Our survey has just started to find potential Our survey has just started to find potential planetary host stars with age planetary host stars with age 10 Myr 10 Myr

NIR spectroscopy has to be obtained to verify NIR spectroscopy has to be obtained to verify planetary companionsplanetary companions


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

Documents

weise rv survey of stars

rv variation34

rv stable184

survey208 stars

rv measurementsfirst

young accreating stars

circumstellar disksmeasurable

circumstellar disks24