OGLE2-TR-L9 b

OGLE2-TR-L9: An extrasolar planet transiting a fast-rotating F3 star

http://arxiv.org/abs/0812.0599

Abstract wrote:

Context: Photometric observations for the OGLE-II microlens monitoring campaign have been taken in the period 1997-2000. All light curves of this campaign have recently been made public. Our analysis of these data has revealed 13 low-amplitude transiting objects among ~15700 stars in three Carina fields towards the galactic disk. One of these objects, OGLE2-TR-L9 (P~2.5 days), turned out to be an excellent transiting planet candidate.
Aims: In this paper we report on our investigation of the true nature of OGLE2-TR-L9, by re-observing the photometric transit with the aim to determine the transit parameters at high precision, and by spectroscopic observations, to estimate the properties of the host star, and to determine the mass of the transiting object through radial velocity measurements.
Methods: High precision photometric observations have been obtained in g', r', i', and z' band simultaneously, using the new GROND detector, mounted on the MPI/ESO 2.2m telescope at La Silla. Eight epochs of high-dispersion spectroscopic observations were obtained using the fiber-fed FLAMES/UVES Echelle spectrograph, mounted on ESO's Very Large Telescope at Paranal.
Results: The photometric transit, now more than 7 years after the last OGLE-II observations, was re-discovered only ~8 minutes from its predicted time. The primary object is a fast rotating F3 star, with vsini=39.33+-0.38 km/s, T=6933+-58 K, log g = 4.25+-0.01, and [Fe/H] = -0.05+-0.20. The transiting object is an extrasolar planet with M_p=4.5+-1.5 M_Jup and R_p=1.61+-0.04 R_Jup. The rejection of possible blend scenarios was based on a quantitative analysis of the multi-color photometric data [abridged].

Finally confirmed. The Hot Jupiter has quite a "bloated" radius, close to that of TrES-4b. And it's nearly as massive as Tau Bootis b.

Very interesting! Found by undergrad students during a search algorithm project. Very inspiring!

The claims that OGLE2-TR-L9 is the hottest star to host a planetary companion, however, are simply untrue, due to the discovery of three solar systems with A-type stars. Still, this star is rather hot for a RV detection of a planet.

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The discovery paper also makes the claim of the hottest exoplanet host star. It may be that the paper was written before the announcement of Fomalhaut b and friends. Perhaps also the writer of the article just took information from this paper. Perhaps the writer of the article didn't know Fomalhaut was a hotter star, so just went along with it.

I find it curious that the writers of the paper did not edit their paper accordingly after Fomalhaut b, HR 8799 b, c, d, and Bet Pic b were all announced.

New Parameters and Transit Timing Studies for OGLE2-TR-L9 b
http://arxiv.org/abs/1007.0589

Abstract wrote:

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 2454492.80008(+/- 0.00014) + 2.48553417(+/- 6.4) x 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{\deg} (+/- 0.12), differing significantly in a and inc from the previously published values. Within our data, we find indications for TTVs.

wow, the planet got bigger by 0.05 of a Jupiter radius.