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Post Info TOPIC: OGLE2-TR-L9b


Posts: 131433

Title: OGLE2-TR-L9: An extrasolar planet transiting a fast-rotating F3 star
Authors: I.A.G. Snellen, J. Koppenhoefer, R.F.J. van der Burg, S. Dreizler, J. Greiner, M.D.J. de Hoon, T.O. Husser, T. Kruhler, R.P. Saglia, F.N. Vuijsje

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=39.330.38 km/s, T=693358 K, log g = 4.250.01, and [Fe/H] = -0.050.20. The transiting object is an extrasolar planet with M_p=4.51.5 M_Jup and R_p=1.610.04 R_Jup. The rejection of possible blend scenarios was based on a quantitative analysis of the multi-colour photometric data.

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Posts: 131433

Three undergraduate students, from Leiden University in the Netherlands, have discovered an extrasolar planet. The extraordinary find, which turned up during their research project, is about five times as massive as Jupiter. This is also the first planet discovered orbiting a fast-rotating hot star.
Omega Centauri
The students were testing a method of investigating the light fluctuations of thousands of stars in the OGLE database in an automated way. The brightness of one of the stars was found to decrease for two hours every 2.5 days by about one percent. Follow-up observations, taken with ESO's Very Large Telescope in Chile, confirmed that this phenomenon is caused by a planet passing in front of the star, blocking part of the starlight at regular intervals.
According to Ignas Snellen, supervisor of the research project, the discovery was a complete surprise.

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