Characterisation of extrasolar planetary transit candidates

Abstract

The detection of transits is an efficient technique to uncover faint companions around stars. The full characterisation of the companions (M-type stars, brown dwarfs or exoplanets) requires high-resolution spectroscopy to measure properly masses and radii. With the advent of massive variability surveys over wide fields, the large number of possible candidates makes such a full characterisation impractical for all of them. We explore here a fast technique to pre-select the most promising candidates using either near-IR photometry or low resolution spectroscopy. We develop a new method based on the well-calibrated surface brightness relation along with the correlation between mass and luminosity for main sequence stars, so that not only giant stars can be excluded but also accurate effective temperatures and radii can be measured. The main source of uncertainty arises from the unknown dispersion of extinction at a given distance. We apply this technique to our observations of a sample of 34 stars extracted from the 62 low-depth transits identified by OGLE during their survey of some 10e5 stars stars in the Carina fields of the Galactic disc. We infer that at least 78% of the companions of the stars which are well characterised in this sample are not exoplanets. Stars OGLE-TR-105, OGLE-TR-109 and OGLE-TR-111 are the likeliest to host exoplanets and deserve high-resolution follow-up studies. OGLE-TR-111 was very recently confirmed as an exoplanet with M_planet = 0.53 +- 0.1 M_Jup (Pont et al. 2004), confirming the efficiency of our method in pre-selecting reliable planetary transit candidates.

31 pages, 17 figures. Astronomy & Astrophysics, in press

References in corpus (14)

• Spectroscopic [Fe/H] for 98 extra-solar planet-host stars: Exploring the probability of planet formation
• The angular size of dwarf stars and subgiants - Surface brightness relations calibrated by interferometry
• A three-dimensional Galactic extinction model
• Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: I. The HI Disk
• Two new "very hot Jupiters" among the OGLE transiting candidates
• The "missing link": a 4-day period transiting exoplanet around OGLE-TR-111
• Testing blend scenarios for extrasolar transiting planet candidates. I. -- OGLE-TR-33: a false positive
• What Fraction of Sun-like Stars have Planets?
• High-resolution spectroscopic follow-up of OGLE planetary transit candidates in the Galactic bulge: two possible Jupiter-mass planets and two blends
• On the Selection of Photometric Planetary Transits
• A Search for Planets in the Old Open Cluster NGC 6791
• Ellipsoidal Variability in the OGLE Planetary Transit Candidates
• Searching for Planetary Transits in the Field of Open Cluster NGC 6819 - I
• Effective temperatures and radii of planet-hosting stars from IR photometry

Cited by in corpus (10)

• Homogeneous studies of transiting extrasolar planets. II. Physical properties
• Searching for Transiting Planets in Stellar Systems
• Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates III: Accurate Radius and Period for OGLE-TR-111-b
• Lack of Transit Timing Variations of OGLE-TR-111b: A re-analysis with six new epochs
• Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates: II. Transits of OGLE-TR-113-b in the Optical and Near-IR
• Search for Planetary Candidates within the OGLE Stars
• Millimagnitude Optical Photometry for the Transiting Planetary Candidate OGLE-TR-109
• Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates IV: The Puzzle of the Extremely Red OGLE-TR-82 Primary Solved
• Asteroseismology of Solar-type stars with Kepler II: Stellar Modeling
• Spectral types of planetary host star candidates from OGLE III