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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.

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

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  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

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