1. Adriana V. R. Silva CRAAM/Mackenzie COROT 2005 01/11/2005

2.  Regions of high concentration of magnetic fields;  Indicators of magnetic activity cycle;  Understanding of solar activity: –solar flares, coronal mass ejections, etc;  Currently it is not possible to detect, let alone monitor the behavior of solar like spots on other stars due to their very small sizes.

3.  Mercury transit on November 15, 1999, that lasted about 1 hour.

4.  During one of its transits, an exoplanet may pass in front of a stellar group of spots.  A method for studying the physical characteristics of starspots based on planet- ary transits is proposed.  Observations of HD 209458 are used to test the model.  Silva, ApJ Letters, 585, L147-L150, 2003.

5.  169 planets detected presently.  9 transiting: HD 209458, TrES-1, OGLE-10, 56, 111, 113, 132, HD 189733, HD 149026.  Data from HD 209458: –April 25, 2000 (Brown et al. 2001) with the Hubble Space Telescope (HST); –July 26, 2000 (Deeg et al. 2001) with the 0.9 telescope of the Observatorio Sierra Nevada.

6.  Two observations with “bumps” in the light curve were used: Deeg et al. (2001) Brown et al. (2001) - HST

7.  Star  white light image of the Sun  Planet  opaque disk of radius r/R s  Transit: at each time the planet is centered at a given position in its orbit (a orb /R s and i)  calculate the integrated flux  Search in parameter space for the best values of r /R s, a orb /R s, and i (minimum  2)

9.  Planet in a circular orbit around HD 209458 with a period of 3.5247 days, major semi-axis of 0.0467 AU, and inclination angle, i=86,68.  Planet radius = 1.347 R Jup, and stellar radius = 1.146 R Sun.  The planet is represented by an opaque disk that crosses the stellar disk at 30.45° latitude (corresponding to i=86,68).  The planet position is calculated every two minutes.  Lightcurve intensity at every two minutes is the sum of all the pixels values in the image.

10.  The spots were modeled by three parameters:  Intensity, as a function of stellar intensity at disk center (max);  Size, as a function of planet radius;  Position, as a distance to the transit line in units of planet radius.

11. Transit with spots without spots

12.  HST data (Brown et al. 2001) is not well fit by the model, indicating that the limb darkening of HD209458 is not a linear function of , as that of the Sun, instead it is best described by a quadratic function (  =cos  ). quadratic linear quadratic

13.  Star represented by a quadratic limb darkening with w1=0.2925 and w2=0.3475 (Brown et al. 2001).  Spot modeled by three parameters: –Intensity, as a function of stellar intensity at disk center (max); –Size, as a function of planet radius; –Position, as a distance to the transit line in units of planet radius.

14. Transit with spots without spots

15.  Starspot temperature, T 0, estimated from blackbody emission, where T e is the stellar surface temperature assumed to be 6000+50 K (Mazeh et al. 2000):  Starspot temperatures between 4900-5000 K. SPOTS 26-jul-200025-apr-2000 Radius (R p )0.4-0.60.3-0.4 Intensity (I star )0.4-0.60.5-0.7 Distance to transit line (R p ) 0.5-0.80.7-0.9 R p =9.4 10 4 km

16.  This method enables us to estimate the starspots physical parameters.  From modeling HD208458 data, we obtained the starspots characteristics: –sizes of 3-6 10 4 km, being larger than regular sunspots, usually of the order of 11000 km (probably a group of starspots, similar to solar active regions). –temperatures of 4900 - 5500 K, being hotter than regular sunspots (3800-4400K), however the surface temperature of HD 209458, 6000K, is also hotter than that of the Sun (5780K). Nevertheless, the sunspots seen in the white light image are also about 0.4-0.7 of the solar disk center intensity, similarly to what was obtained from the model. –Location latitude.

18. sunspot eclipse  Small variations in the lightcurve during the planetary transit caused by the planet occultation of starspots.  Uncertainty of ~0.0001 in flux. 1.5 Earth size Planet Jupiter size Planet phase Relative flux

19. 26 April 200029 April 2000 starspot

20.  Subtracting the lightcurve taken 3 days later, measure the  f between the starspot position.  Rotation period of the star:  P s =27.6 days 26 th 29 th phase Relative flux ff I(26 th )-I(29 th )

21.  Core programme data;  Observations of planetary transits with: –  I/I~0.0001 –Temporal resolution of few minutes  Results expected: –Starspot characteristics (size, temperature, location, evolution); –Starspot structure for Earth size planets; –Limb darkening  temperature gradient of the stellar photosphere; –Stellar rotation (solar-like stars: 150 days ~ 5 periods)  Extra: –Differential rotation (planets at different latitudes); –Activity cycles (for short cycles)