OGLE-TR-10 b

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**OGLE-TR-10 b**
Parent star
Extrasolar planet		List of extrasolar planets
Star		OGLE-TR-10
Constellation		Sagittarius
Right ascension	(α)	17^h 51^m 28.25^s
Declination	(δ)	-29° 52' 34.9"
Distance		~5000 ly (~1500 pc)
Spectral type		G or K
Orbital elements
Semimajor axis	(a)	0.04162 ± 0.00004 AU
Orbital period	(P)	3.10129 ± 0.00001 d
Inclination	(i)	84.5 ± 0.6°
Angular distance	(θ)	0.028 mas
Semi-amplitude	(K)	100 ± 43 m/s
Physical characteristics
Mass	(m)	0.63 ± 0.14 M_J
Radius	(r)	1.26 ± 0.07 R_J
Density	(ρ)	420 kg/m³
Surface gravity	(g)	0.94 g
Discovery information
Discovery date		Nov 26, 2002
Discoverer(s)		Konacki et al.
Detection method		Transit
Discovery site		Las Campanas Observatory in Chile
Discovery status		Confirmed

OGLE-TR-10b is an extrasolar planet orbiting the star OGLE-TR-10.

The planet was first detected by the Optical Gravitational Lensing Experiment (OGLE) survey in 2002. The star, OGLE-TR-10, was seen dimming by a tiny amount every 3 days. The transit lightcurve resembles that of HD 209458b, the first transiting extrasolar planet. However, the mass of the object had to be measured by the radial velocity method, because other objects like red dwarfs and brown dwarfs can mimic the planetary transit. In late 2004 it was confirmed as the 5th planetary discovery by OGLE.

The planet is a typical "hot Jupiter", a planet with a mass half that of Jupiter and orbital distance only 1/24th that of Earth from the Sun. One revolution around the star takes a little over three days to complete. The planet is slightly larger than Jupiter, probably due to the heat from the star.

OGLE-TR-10 was identified as a promising candidate by the OGLE team during their 2001 campaign in three fields towards the Galactic center (Andrzej Udalski et al, 2002). The possible planetary nature of its companion based on spectroscopic follow-up was first established by Konacki et al (2003). We reported a tentative radial velocity semi-amplitude (from Keck-I/HIRES) of 100+/-43 m/s, and a mass for the putative planet of 0.7 +/- 0.3 MJup. This was confirmed by Bouchy et al (2004) with their UVES/FLAMES radial velocities. However, the possibility of a blend could not be ruled out.

Now we are able to rule out a blend scenario as an alternative explanation. From an analysis combining all available radial velocity measurements with the OGLE light curve we find that OGLE-TR-10b has a mass of 0.57 +/- 0.12 MJup and a radius of 1.24 +/- 0.09 RJup. These parameters bear close resemblance to those of the first known transiting extrasolar planet, HD 209458b.

Note an apparent dichotomy in the mass-radius diagram in that the 4 planets with the longer periods (in the hot Jupiter class) all have small masses (~0.7 MJup), while all the short-period planets (very hot Jupiters) have masses roughly twice as large. This trend, noted previously by Mazeh et al (2005), now seems to be reinforced, and may perhaps be related to issues of survival of planets in proximity to their parent stars.