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CoRoT-18 b: Analysis of High-Precision Transit Light Curves with Starspot Features

Raetz St., Heras A. M., Gondoin P., Fernández M., Casanova V., Schmidt T. O. B., Maciejewski G.

Acta Astronomica

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2019

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Vol. 69, No. 3

205--226

EN

When a planet occults a spotty area on a stellar surface, the flux increases and a characteristic feature in a light curve - a bump - is observed. Among the planets detected by the CoRoT-mission CoRoT-18 is especially interesting as it exhibited spot crossings that we have analyzed in detail. We used four ground-based observations obtained at a 1.5-m telescope in Spain and the 13 available CoRoT-transits to refine and constrain stellar, planetary and geometrical parameters of the system. We found that the derived physical properties slightly deviate from the previously published values, most likely due to the different treatment of the stellar activity. Following of a spot over several transits enabled us to measure the stellar rotation period and the spin-orbit alignment. Our derived values of Prot=5.19±0.03 d and λ=6±13° are in agreement with the literature values that were obtained with other methods. Although we cannot exclude a very old age for CoRoT-18, our observations support the young star hypothesis and, hence, yield constraints on the time-scale of planet formation and migration.

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New Transit Observations for HAT-P-30 b, HAT-P-37 b, TrES-5 b, WASP-28 b, WASP-36 b and WASP-39 b

Maciejewski G., Dimitrov D., Mancini L., Southworth J., Ciceri S., D'Ago G., Bruni I., Raetz St., Nowak G., Ohlert J., Puchalski D., Saral G., Derman E., Petrucci R., Jofre E., Seeliger M., Henning T.

Acta Astronomica

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2016

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Vol. 66, No. 1

55--74

EN

We present new transit light curves for planets in six extrasolar planetary systems. They were acquired with 0.4-2.2 m telescopes located in west Asia, Europe, and South America. When combined with literature data, they allowed us to redetermine system parameters in a homogeneous way. Our results for individual systems are in agreement with values reported in previous studies. We refined transit ephemerides and reduced uncertainties of orbital periods by a factor between 2 and 7. No sign of any variations in transit times was detected for the planets studied.

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Revisiting Parameters for the WASP-1 Planetary System

Maciejewski G., Ohlert J., Dimitrov D., Puchalski D., Nedoroščík J., Vaňko M., Marka C., Baar S., Raetz St., Seeliger M., Neuhäuser R.

Acta Astronomica

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2014

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Vol. 64, No. 1

27--43

EN

We present thirteen new transit light curves for the WASP-1b exoplanet. Observations were acquired with 0.5 m-1.2 m telescopes between 2007 and 2013. Our homogeneous analysis, which also includes the literature data, results in determining precise system parameters. New values are in agreement with those reported in previous studies. Transit times follow a linear ephemeris with no sign of any transit time variations. This finding is in line with the paradigm that Jupiter-like planets on tight orbits are devoid of close planetary companions. Key words: planetary systems - Stars: individual: WASP-1 - Planets and satellites: individual: WASP-1b

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Refining Parameters of the XO-5 Planetary System with High-Precision Transit Photometry

Maciejewski G., Seeliger M., Adam Ch., Raetz St., Neuhäuser R.

Acta Astronomica

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2011

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Vol. 61, No. 1

25--35

EN

Studies of transiting extrasolar planets provide unique opportunity to get to know the internal structure of those worlds. The transiting exoplanet XO-5 b was found to have an anomalously high Safronov number and surface gravity. Our aim was to refine parameters of this intriguing system and search for signs of transit timing variations. We gathered high-precision light curves for two transits of XO-5 b. Assuming three different limb darkening laws, we found the best-fitting model and redetermined parameters of the system, including planet-to-star radius ratio, impact parameter and central time of transits. Error estimates were derived by the prayer bead method and Monte Carlo simulations. Although system's parameters obtained by us were found to agree with previous studies within one sigma, the planet was found to be notable smaller with the radius of 1.03+0.06-0.05 Jupiter radii. Our results confirm the high Safronov number and surface gravity of the planet. With two new mid-transit times, the ephemeris was refined to BJDTDB=(2454485.66842±0.00028)+(4.1877537±0.000017)E. No significant transit timing variation was detected.