DTECTION DEXOPLANTES EN TRANSIT ETIMPACT DE LACTIVIT STELLAIRE

Roxanne LIGIDoctorante sous la direction de Denis MourardObservatoire de la Cte dAzur, Nice, FranceLaboratoire Lagrange, UNS/CNRS/OCA

EN INTERROMTRIE OPTIQUE

IntroductionNowadays, more than 800 exoplanets have been detectedRadial velocity (RV): most prolific methodTransit method (a few thousand Kepler candidates)AstrometryMicrolensing

Difficulties to characterize them:RV Mpl sin i / M*Transit method Rpl / R*

Better precision on the stars parameters exoplanets parameters.

04/06/13R. LIGI - SF2A 2013*

R. LIGI - SF2A 2013

1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.1 Choice of targetsNow 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 stars0.3 mas < * < 3 masMag V < 6.5 and Mag K < 6.5-30 < < +90Observations from April to December

Host stars accessible with VEGA/CHARA: 42 stars. 35.7% V52.4% III11.9% IV

04/06/13R. LIGI - SF2A 2013*Among them, only 1transiting exoplanet, BUT 18transiting exoplanets withmagV

Six 1-m telescopes arranged in Y-shape.

Baselines between 34m and 331m.

VEGA: Visible spEctoGrAph and interferometerUp to 4T configuration, but mainly 3TV bandResolution: 6000/30000

04/06/13R. LIGI - SF2A 2013*1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 VEGA

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14 AndHD221345, HIP116076, HR8930One exoplanet: 4.8 MJupK0IIIV mag = 5.22, K mag = 2.33(Sato et al., 2008)

AndHD9826, HIP7513, HHosts four exoplanetsF9V(Furhmann et al., 1998))

42 DraHD170693, HIP513, HOne exoplanet: 3.880.85 MjupK1.5III(Dllinger et al., 2009)

CygHD185395F4VKepler targetQuasi-periodical radial velocity of ~150 days unexplained (with ELODIE and SOPHIE, OHP)(Desort et al., 2009).

04/06/13R. LIGI - SF2A 2013*1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 Published Results (Ligi et al., 2012)

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LD = 1.18 0.01 mas2reduced = 6.9UD = 1.12 0.01 mas

LD = 2.12 0.02 mas2reduced = 0.199LD = 1.97 0.02 mas

LD = 1.51 0.02 mas2reduced = 2.769UD = 1.40 0.02 mas

LD = 0.76 0.003 mas2reduced = 8.5LD = 0.726 0.032 mas

04/06/13R. LIGI - SF2A 2013*1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 Published Results (Ligi et al., 2012)

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Radius:

Mass:

Effective temperature: Results in good agreements with results found in the litterature!04/06/13R. LIGI - SF2A 2013*1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 Published Results (Ligi et al., 2012)

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HD167042Host star, UD expected 0.80 mas, magV = 5.971 exoplanet2 obervations, 720 nmUD meas. 1.000.014 mas2red = 0.58

HD 3651Host stars UD expected 0.70 mas, magV = 5.801 exoplanet2 observations, 720 nmUD meas. 1.150.015 mas 2red = 0.5055 CancriHost star, UD expected 0.70 mas, magV = 5.955 exoplanets, (1 transiting).3 observations, 720 nmUD meas. 0.630.011 mas2red = 0.4304/06/13R. LIGI - SF2A 2013*1. INTERFEROMETRIC STUDY OF EXOPLANET HOST STARS1.2 On-going Results (Ligi et al., in prep.)

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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

04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.1 COde for Modelling ExoplaneTs and Spots (COMETS)

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Example: 55 Cnc observed with VEGA/CHARA, oifits file made with ASPRO2. pl=0.015 mas.Visibilities: nothing is detected.Closure phase: the signal does not exceed 1.04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.1 COde for Modelling ExoplaneTs and Spots (COMETS) TimeTimeClosure phase (deg)Visibility modulusSpacial frequency (cyc/rad)single starstar+ transiting exoplanet

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Example: 55 Cnc observed with VEGA/CHARA, oifits file made with ASPRO2. pl=0.15 mas.Visibilities: reach 6% difference close to the zero of visibility.Closure phase: the signal reaches 120.04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.1 COde for Modelling ExoplaneTs and Spots (COMETS) Visibility modulusSpacial frequency (cyc/rad)Closure phase (deg)TimeTimesingle starstar+ transiting exoplanet

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We fix all parameters but one, and make it vary.Fixed values: *=1 mas, Ipl=0, x=0.2 mas, =0.5.Variation:Of x: from 0 to 0.5 masOf pl: from 0.04 to 0.24Of for studying the impact of LD: from 0.44 to 0.74., x fixed, and variation of pl/* (steady ratio)., x, spot, * fixed, variation of Ispot.04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.2 Methodom,Iom

pen, Ipen

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+ 2% difference* 1% difference 2 difference 20 differenceVariation of the Visibility: No solution is found for pl< 0.13 mas for 2% difference. For pl< 0.09 mas, much larger baselines are needed.

Variation of the closure phase: CHARA baselines exist.04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.3 Results

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For exoplanetsIn general, very small exoplanets (pl< 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 visibilityFor now, only big exoplanets (hot Jupiter, Neptune-like planets) have a chance to be detected by interferometry.

For spotsLess contrast with spots than exoplanets need bigger baselines

The intensity of the spot would allow to disentangle between spots and exoplanets.

04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.3 Results

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Legend:

Single star

Star + transiting exoplanet

Star + spot

Star + spot and exoplanet

One direction, pl = om= 0.15 mas, , p*= 1 mas.Maximum difference of 0.4% for exoplanet+ spotBetter seen in the 1st and 2nd lobe of visibility04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.4 Comparison between exoplanets and spots

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Maximum difference of 150 for exoplanet+ spotBetter seen on the transitions04/06/13R. LIGI - SF2A 2013*2. MODELLING OF EXOPLANET HOST STARS AND SPOTS 2.4 Comparison between exoplanets and spotsLegend:

Single star

Star + transiting exoplanet

Star + spot

Star + spot and exoplanet

One direction, pl = om= 0.15 mas, , p*= 1 mas.

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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..04/06/13R. LIGI - SF2A 2013*CONCLUSION

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MERCIde votre attention04/06/13*

**pourquoi 2% de prcision ? dire que je donnerai les formules plus tard.**juste avant : slide de traitement de donnes de VEGA (avec un diagramme)*Work still in progress.Generally bad weather in 2012, and instrumental difficulties prevented us to get good data in general.Diameters to be confirmed, and stars parameters to be calculated.

When conditions are good, we get good precisions on the measured diameters (2-3 %).We still have data to reduce in order to complete the star sample of 2012.

*schmas pour illustrerevaluation by analytical formula and numerical computation = avantage

*frise avec les images **mettre work in progress : bcp de bruit !**