Issue |
A&A
Volume 497, Number 2, April II 2009
|
|
---|---|---|
Page(s) | 545 - 550 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/200810917 | |
Published online | 09 February 2009 |
OGLE2-TR-L9b: an exoplanet transiting a rapidly rotating F3 star*
1
Leiden Observatory, Leiden University, Postbus 9513, 2300 RA, Leiden, The Netherlands e-mail: snellen@strw.leidenuniv.nl
2
Universitäts-Sternwarte München, Munich, Germany
3
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
4
Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
5
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
6
Universe Cluster, Technische Universität München, Boltzmannstraße 2, 85748, Garching, Germany
Received:
5
September
2008
Accepted:
5
December
2008
Context. The photometric observations of the OGLE-II microlens monitoring
campaign have been taken in the period 1997-2000. All light curves of this campaign have recently become public. Our analysis of these data has revealed 13 low-amplitude transiting objects among
~15 700 stars in three Carina fields towards the Galactic disk. One of
these objects, OGLE2-TR-L9 ( days), turned out to be an excellent
transiting-planet candidate.
Aims. We report on our investigation of the true nature of OGLE2-TR-L9. By re-observing the photometric transit, we attempt to determine the transit parameters to high precision, and, by spectroscopic observations, to estimate the properties of the host star and determine the mass of the transiting object by means of radial-velocity measurements.
Methods. High precision photometric observations were obtained in g', r', i', and z' band simultaneously, using the new GROND detector, mounted on the MPI/ESO 2.2 m 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 min from its
predicted time. The primary object is a rapidly rotating F3 star with
km s-1,
K,
, and
. The transiting object is an extrasolar planet
with
and
. Since this is the first planet
detected orbiting a fast rotating star, the uncertainties
in both the radial-velocity measurements and the planetary mass are larger than
for most other planets discovered to date. The rejection of possible blend scenarios was based on a quantitative analysis of the multi-color photometric data. A stellar-blend scenario
of an early F-star with a faint eclipsing-binary system is excluded, due to
1) the consistency between the spectroscopic parameters of the
star and the mean density of the transited object as determined from
the photometry, and 2) the excellent agreement between the transit signal
as observed at four different wavelengths.
Key words: stars: planetary systems / techniques: photometric / eclipses / stars: rotation
© ESO, 2009
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