1 / 18

DÉTECTION D ’ EXOPLANÈTES EN TRANSIT ET IMPACT DE L ’ ACTIVITÉ STELLAIRE

DÉTECTION D ’ EXOPLANÈTES EN TRANSIT ET IMPACT DE L ’ ACTIVITÉ STELLAIRE. Roxanne LIGI Doctorante sous la direction de Denis Mourard Observatoire de la Côte d ’ Azur, Nice, France Laboratoire Lagrange, UNS/CNRS/OCA. EN INTERÉROMÉTRIE OPTIQUE. Introduction.

morna
Télécharger la présentation

DÉTECTION D ’ EXOPLANÈTES EN TRANSIT ET IMPACT DE L ’ ACTIVITÉ STELLAIRE

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. DÉTECTION D’EXOPLANÈTES EN TRANSIT ETIMPACT DE L’ACTIVITÉ STELLAIRE Roxanne LIGI Doctorante sous la direction de Denis Mourard Observatoire de la Côte d’Azur, Nice, France Laboratoire Lagrange, UNS/CNRS/OCA EN INTERÉROMÉTRIE OPTIQUE

  2. Introduction • Nowadays, more than 800 exoplanets have been detected • Radial velocity (RV): most prolific method • Transit method (a few thousand Kepler candidates) • Astrometry • Microlensing… • Difficulties to characterize them: • RV  Mpl sin i / M* • Transit method  Rpl / R* • Better precision on the stars parameters  exoplanets parameters. R. LIGI - SF2A 2013

  3. 1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.1 Choice of targets • Now able to measure diameters with 2% accuracy, which allows having sufficient informations on fundamental parameters (mass, radius, temperature). • Exoplanet host stars observable by VEGA/CHARA: • F, G, K type stars • 0.3 mas < θ* < 3 mas • Mag V < 6.5 and Mag K < 6.5 • -30° < δ < +90° • Observations from April to December • Host stars accessible with VEGA/CHARA: 42 stars. • 35.7% V • 52.4% III • 11.9% IV Among them, only 1 transiting exoplanet, BUT 18 transiting exoplanets with magV<10 that will be observable with VEGAS, VEGA second generation... R. LIGI - SF2A 2013

  4. 1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 VEGA • Six 1-m telescopesarranged in Y-shape. • Baselinesbetween 34m and 331m. • VEGA: Visible spEctoGrAph and interferometer • Up to 4T configuration, but mainly 3T • V band • Resolution: 6000/30000 R. LIGI - SF2A 2013

  5. 1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 Published Results (Ligi et al., 2012) 42 Dra HD170693, HIP513, H One exoplanet: 3.88±0.85 Mjup K1.5III (Döllinger et al., 2009) θ Cyg HD185395 F4V Kepler target Quasi-periodical radial velocity of ~150 days unexplained (with ELODIE and SOPHIE, OHP) (Desort et al., 2009). • 14 And • HD221345, HIP116076, HR8930 • One exoplanet: 4.8 MJup • K0III • V mag = 5.22, K mag = 2.33 • (Sato et al., 2008) • υAnd • HD9826, HIP7513, H • Hosts four exoplanets • F9V • (Furhmann et al., 1998)) R. LIGI - SF2A 2013

  6. 1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 Published Results (Ligi et al., 2012) θLD = 1.18 ± 0.01 mas χ2reduced = 6.9 θUD = 1.12 ± 0.01 mas θLD = 2.12 ± 0.02 mas χ2reduced = 0.199 θLD = 1.97 ± 0.02 mas θLD = 0.76 ± 0.003 mas χ2reduced = 8.5 θLD = 0.726 ± 0.032 mas θLD = 1.51 ± 0.02 mas χ2reduced = 2.769 θUD = 1.40 ± 0.02 mas R. LIGI - SF2A 2013

  7. 1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 Published Results (Ligi et al., 2012) • Radius: • Mass: • Effective temperature: Results in good agreementswithresultsfound in the litterature! R. LIGI - SF2A 2013

  8. 1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 On-going Results (Ligi et al., in prep.) • HD167042 • Host star, θUD expected ≈ 0.80 mas, magV = 5.97 • 1 exoplanet • 2 obervations, 720 nm • θUD meas. ≈ 1.00±0.014 mas • χ2red = 0.58 • 55 Cancri • Host star, θUD expected ≈ 0.70 mas, magV = 5.95 • 5 exoplanets, • (1 transiting). • 3 observations, 720 nm • θUD meas. ≈ 0.63±0.011 mas • χ2red = 0.43 • HD 3651 • Host stars θUD expected ≈ 0.70 mas, magV = 5.80 • 1 exoplanet • 2 observations, 720 nm • θUD meas. ≈ 1.15±0.015 mas • χ2red = 0.50 R. LIGI - SF2A 2013

  9. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.1 COde for Modelling ExoplaneTs and Spots (COMETS) • Evaluate the detectivity of exoplanets by interferometry in the visible (taking into account periodical noises such as spots). • Impact of stellar noises, like magnetic spots? • RV (Lagrange et al. 2010, Meunier et al. 2010). • IR interferometry (Matter et al., 2010).-> exoplanets • COMETS (COde for Modeling ExoplaneTs and Spots): modelling of visibilities and closure phases for exoplanets and spots, obtained with VEGA/CHARA or a fictive (u,v) plan. • Evaluation by analytical formula and numerical computation. • IDL code R. LIGI - SF2A 2013

  10. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.1 COde for Modelling ExoplaneTs and Spots (COMETS) Example: 55 Cnc observed with VEGA/CHARA, oifits file made with ASPRO2. θpl=0.015 mas. • Visibilities: nothing is detected. • Closure phase: the signal does not exceed 1°. single star star+ transiting exoplanet Visibility modulus Closure phase (deg) Time Time Spacial frequency (cyc/rad) R. LIGI - SF2A 2013

  11. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.1 COde for Modelling ExoplaneTs and Spots (COMETS) Example: 55 Cnc observed with VEGA/CHARA, oifits file made with ASPRO2. θpl=0.15 mas. • Visibilities: reach 6% difference close to the zero of visibility. • Closure phase: the signal reaches 120°. single star star+ transiting exoplanet Visibility modulus Closure phase (deg) Spacial frequency (cyc/rad) Time Time R. LIGI - SF2A 2013

  12. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.2 Method • We fix all parameters but one, and make it vary. • Fixed values: θ*=1 mas, Ipl=0, x=0.2 mas, α=0.5. • Variation: • Of x: from 0 to 0.5 mas • Of θpl: from 0.04 to 0.24 • Of α for studying the impact of LD: from 0.44 to 0.74. • α, x fixed, and variation of θpl/θ* (steady ratio). • α, x, θspot, θ* fixed, variation of Ispot. θpen,Ipen θom,Iom R. LIGI - SF2A 2013

  13. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.3 Results Variation of the Visibility: No solution is found for θpl< 0.13 mas for 2% difference. For θpl< 0.09 mas, much larger baselines are needed. Variation of the closure phase: CHARA baselinesexist. + 2% difference * 1% difference 2° difference 20° difference R. LIGI - SF2A 2013

  14. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.3 Results • For exoplanets • In general, very small exoplanets (θpl< 0.10 mas) need MBL>200m to be detected on the closure phase. • Having more than 2% difference on the visibilities is not possible. • Need of the closure phases more than the visibility • For now, only big exoplanets (hot Jupiter, Neptune-like planets) have a chance to be detected by interferometry. • For spots • Less contrast with spots than exoplanets  need bigger baselines • The intensity of the spot would allow to disentangle between spots and exoplanets. R. LIGI - SF2A 2013

  15. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.4 Comparison between exoplanets and spots Legend: Single star Star + transiting exoplanet Star + spot Star + spot and exoplanet One direction, θpl = θom= 0.15 mas, , θp*= 1 mas. • Maximum difference of 0.4% for exoplanet+ spot • Better seen in the 1st and 2nd lobe of visibility R. LIGI - SF2A 2013

  16. 2. MODELLING OF EXOPLANET HOST STARS AND SPOTS2.4 Comparison between exoplanets and spots Legend: Single star Star + transiting exoplanet Star + spot Star + spot and exoplanet One direction, θpl = θom= 0.15 mas, , θp*= 1 mas. • Maximum difference of 150° for exoplanet+ spot • Better seen on the transitions R. LIGI - SF2A 2013

  17. CONCLUSION • Exoplanets and spots have a signature in optical interferometry. • More significant signature for exoplanets than for spots for the same size, because the contrast is higher. • With VEGA/CHARA accuracy, we would distinguish spots and exoplanets essentially with the measure of the closure phase, but signature on the visibility for big enough planets and spots. • The presence of spots hardly affects the visibilities, thus the diameters. • Limitation: geometrical model, taking into account only one feature at the time. We could model a full spotted stellar surface for more accuracy, and even with granulation.. R. LIGI - SF2A 2013

  18. MERCIde votre attention

More Related