OGLE2-TR-L9b: an exoplanet transiting a rapidly rotating F3 star

Snellen, I. A. G.; Koppenhoefer, J.; Burg, R. F. J. van der; Dreizler, S.; Greiner, J.; Hoon, M. de; Husser, Tim-Oliver; Krühler, T.; Saglia, R.; Vuijsje, F. N.

doi:10.1051/0004-6361/200810917

Cited by 39 publications

(48 citation statements)

References 24 publications

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“…All values are in good agreement with the values published in Snellen et al (2009) except for a p and inc where our new results are significantly different. The reason for this discrepancy is an error in the calculation of a p in Snellen et al (2009) where 1/M * was used instead of M * when transforming the measured period into a semi-major axis using Kepler's third Law. The error in semimajor axis propagated into a wrong inclination value.…”

Section: Planetary Parameterssupporting

confidence: 91%

“…It should be noted that this "mid-transit point" is derived from an OGLE-II light curve which was constructed from ∼500 data points with irregular cadence collected over a period of 3.5 years. From our new analysis of the transit observed by Snellen et al (2009) on January 27, 2008, we find the central transit time to be HJD 2 454 492.80086 ± 0.00033 instead of HJD 2 454 492.79765 ± 0.00039. All mid-transit times known for OGLE2-TR-L9 can be found in Table 3.…”

Section: A New Ephemerismentioning

confidence: 76%

“…The observations took place during the nights of April 10, 15, 20, 25 and May 15 2009, corresponding to the Epochs 177, 179, 181, 183 and 191 based on the ephemeris given by Snellen et al (2009). During each night, we observed the full transit plus at least 20 min of baseline before ingress and after egress.…”

Section: Observationsmentioning

confidence: 99%

“…The above parameters have the advantage that they can be derived directly from the light curve without assumptions regarding stellar properties other than limb darkening. As starting values, we assumed the central transit times calculated according to the ephemeris given by Snellen et al (2009), and typical values of planetary transits for the other parameters: r p /r * = 0.1, a/r * = 20 and inc = 90 • . After the best parameters were found for each light curve, we used the resulting mid-transit times to phase fold the data producing the light curves shown in Fig.…”

Section: Determination Of System Parametersmentioning

confidence: 99%

“…4. Here epoch −1615 corresponds to the ephemeris derived by Snellen et al (2007) from the OGLE-II data, epoch 0 corresponds to the corrected midtransit time from Snellen et al (2009) and the last five epochs correspond to the newly observed transits. It can be seen that the transit times show some deviations from a constant period as the transit of epoch 0 occurs 1.5 min later and the transit of epoch 179 occurs 1.0 min earlier than expected.…”

Section: Transit Timing and Transit Duration Variationsmentioning

confidence: 99%

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New parameters and transit timing studies for OGLE2-TR-L9 b

Lendl

Afonso

Koppenhoefer

et al. 2010

A&A

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Context. Repeated observations of exoplanet transits allow us to refine the planetary parameters and probe them for any time dependent variations. In particular deviations of the period from a strictly linear ephemeris, transit timing variations (TTVs), can indicate the presence of additional bodies in the planetary system. Aims. Our goal was to reexamine the largely unstudied OGLE2-TR-L9 system with high cadence, multi-color photometry in order to refine the planetary parameters and probe the system for TTVs. Methods. We observed five full transits of OGLE2-TR-L9 with the GROND instrument at the ESO/MPG 2.2 m telescope at La Silla Observatory. GROND is a multichannel imager that allowed us to gather simultaneous light curves in the g , r , i , and z filters.Results. From our analysis we find that the semi-major axis and the inclination differ from the previously published values. With the newly observed transits, we were able to refine the ephemeris to 2 454 492.80008(±0.00014) + 2.48553417(±6.4 × 10 −7 )E. The newly derived parameters are a = 0.0418 ± 0.0015 AU, r p = 1.67 ± 0.05 R j , and inc = 82.47 • ± 0.12, differing significantly in a and inc from the previously published values. Within our data, we find indications for TTVs.

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Section: Planetary Parameterssupporting

confidence: 91%

Section: A New Ephemerismentioning

confidence: 76%

Section: Observationsmentioning

confidence: 99%

Section: Determination Of System Parametersmentioning

confidence: 99%

Section: Transit Timing and Transit Duration Variationsmentioning

confidence: 99%

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New parameters and transit timing studies for OGLE2-TR-L9 b

Lendl

Afonso

Koppenhoefer

et al. 2010

A&A

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A homogeneous spectroscopic analysis of host stars of transiting planets

Eiff

Santos

Sousa

et al. 2009

A&A

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Context. The analysis of transiting extra-solar planets provides an enormous amount of information about the formation and evolution of planetary systems. A precise knowledge of the host stars is necessary to derive the planetary properties accurately. The properties of the host stars, especially their chemical composition, are also of interest in their own right. Aims. Information about planet formation is inferred by, among others, correlations between different parameters such as the orbital period and the metallicity of the host stars. The stellar properties studied should be derived as homogeneously as possible. The present work provides new, uniformly derived parameters for 13 host stars of transiting planets. Methods. Effective temperature, surface gravity, microturbulence parameter, and iron abundance were derived from spectra of both high signal-to-noise ratio and high resolution by assuming iron excitation and ionization equilibria. Results. For some stars, the new parameters differ from previous determinations, which is indicative of changes in the planetary radii. A systematic offset in the abundance scale with respect to previous assessments is found for the TrES and HAT objects. Our abundance measurements are remarkably robust in terms of the uncertainties in surface gravities. The iron abundances measured in the present work are supplemented by all previous determinations using the same analysis technique. The distribution of iron abundance then agrees well with the known metal-rich distribution of planet host stars. To facilitate future studies, the spectroscopic results of the current work are supplemented by the findings for other host stars of transiting planets, for a total dataset of 50 objects.

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Hot Jupiters and the evolution of stellar angular momentum

Lanza¹

2010

A&A

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Context. Giant planets orbiting main-sequence stars closer than 0.1 AU are called hot Jupiters. They interact with their stars affecting their angular momentum. Aims. Recent observations provide evidence of excess angular momentum in stars with hot Jupiters in comparison to stars with distant and less massive planets. This has been attributed to tidal interaction, but needs to be investigated in more detail considering other possible explanations because in several cases the tidal synchronization timescales are much longer than the ages of the stars. Methods. We select stars harbouring transiting hot Jupiters to study their rotation and find that those with an effective temperature T eff > ∼ 6000 K and a rotation period P rot < ∼ 10 days are synchronized with the orbital motion of their planets or have a rotation period approximately twice that of the planetary orbital period. Stars with T eff < ∼ 6000 K or P rot > ∼ 10 days show a general trend toward synchronization with increasing effective temperature or decreasing orbital period. We propose a model for the angular momentum evolution of stars with hot Jupiters to interpret these observations. It is based on the hypothesis that a close-in giant planet affects the coronal field of its host star leading to a topology with predominantly closed field lines. An analytic linear force-free model has been adopted to compute the radial extension of the corona and its angular momentum loss rate. The corona is more tightly confined in F-type stars and in G-and K-type stars with a rotation period shorter than ∼10 days. The angular momentum loss is produced by coronal eruptions similar to solar coronal mass ejections. Results. The model predicts that F-type stars with hot Jupiters, T eff > ∼ 6000 K and an initial rotation period < ∼ 10 days suffer no or very little angular momentum loss during their main-sequence lifetime. This can explain their rotation as a remnant of their premain-sequence evolution. On the other hand, F-type stars with P rot > 10 days and G-and K-type stars experience a significant angular momentum loss during their main-sequence lifetime, but at a generally slower pace than similar stars without close-in massive planets. Considering a spread in their ages, this can explain the observed rotation period distribution of planet-harbouring stars. Conclusions. Our model can be tested observationally and has relevant consequences for the relationship between stellar rotation and close-in giant planets, as well as for the application of gyrochronology to estimate the age of planet-hosting stars.

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OGLE2-TR-L9b: an exoplanet transiting a rapidly rotating F3 star

Cited by 39 publications

References 24 publications

New parameters and transit timing studies for OGLE2-TR-L9 b

New parameters and transit timing studies for OGLE2-TR-L9 b

A homogeneous spectroscopic analysis of host stars of transiting planets

Hot Jupiters and the evolution of stellar angular momentum

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