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Register a new userHAT-P-13b,c: a transiting hot Jupiter with a massive outer companion on an eccentric orbit
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G. A. Bakos
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We report on the discovery of a planetary system with a close-in transiting hot Jupiter on a near circular orbit and a massive outer planet on a highly eccentric orbit. The inner planet, HAT-P-13b, transits the bright V=10.622 G4 dwarf star GSC 3416-00543 every P = 2.916260 pm 0.000010 days, with transit epoch Tc = 2454779.92979 pm 0.00038 (BJD) and duration 0.1345 pm 0.0017 d. The outer planet, HAT-P-13c orbits the star with P2 = 428.5 pm 3.0 days and nominal transit center (assuming zero impact parameter) of T2c = 2454870.4 pm 1.8 (BJD) or time of periastron passage T2,peri= 2454890.05 pm 0.48 (BJD). Transits of the outer planet have not been observed, and may not be present. The host star has a mass of 1.22 pm ^0.05_0.10 Msun, radius of 1.56 pm 0.08 Rsun, effective temperature 5653 pm 90 K, and is rather metal rich with [Fe=H] = +0.41 pm 0.08. The inner planetary companion has a mass of 0.853pm ^0.029_-0.046MJup, and radius of 1.281 pm 0.079 RJup yielding a mean density of 0.498pm +0.103_-0.069 gcm^-3. The outer companion has m2 sini2 = 15.2 pm 1.0 MJup, and orbits on a highly eccentric orbit of e2 = 0.691 pm 0.018. While we have not detected significant transit timing variations of HAT-P-13b, due to gravitational and light-travel time effects, future observations will constrain the orbital inclination of HAT-P-13c, along with its mutual inclination to HAT-P-13b. The HAT-P-13 (b,c) double-planet system may prove extremely valuable for theoretical studies of the formation and dynamics of planetary systems.
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We report the discovery of HAT-P-30b, a transiting exoplanet orbiting the V=10.419 dwarf star GSC 0208-00722. The planet has a period P=2.810595+/-0.000005 d, transit epoch Tc = 2455456.46561+/-0.00037 (BJD), and transit duration 0.0887+/-0.0015 d. The host star has a mass of 1.24+/-0.04 Msun, radius of 1.21+/-0.05 Rsun, effective temperature 6304+/-88 K, and metallicity [Fe/H] = +0.13+/-0.08. The planetary companion has a mass of 0.711+/-0.028 Mjup, and radius of 1.340+/-0.065 Rjup yielding a mean density of 0.37+/-0.05 g cm^-3. We also present radial velocity measurements that were obtained throughout a transit that exhibit the Rossiter-McLaughlin effect. By modeling this effect we measure an angle of lambda = 73.5+/-9.0 deg between the sky projections of the planets orbit normal and the stars spin axis. HAT-P-30b represents another example of a close-in planet on a highly tilted orbit, and conforms to the previously noted pattern that tilted orbits are more common around stars with Teff > 6250 K.
Transiting planets orbiting bright stars are the most favorable targets for follow-up and characterization. We report the discovery of the transiting hot Jupiter XO-7 b and of a second, massive companion on a wide orbit around a circumpolar, bright, and metal rich G0 dwarf (V = 10.52, $T_{rm eff} = 6250 pm 100 ; rm K$, $rm[Fe/H] = 0.432 pm 0.057 ; rm dex$). We conducted photometric and radial velocity follow-up with a team of amateur and professional astronomers. XO-7 b has a period of $ 2.8641424 pm 0.0000043$ days, a mass of $0.709 pm 0.034 ; rm M_{rm J}$, a radius of $1.373 pm 0.026 ; rm R_{rm J}$, a density of $0.340 pm 0.027 ; rm g , {cm}^{-3}$, and an equilibrium temperature of $1743 pm 23 ; rm K$. Its large atmospheric scale height and the brightness of the host star make it well suited to atmospheric characterization. The wide orbit companion is detected as a linear trend in radial velocities with an amplitude of $sim100 ; rm m , {s}^{-1}$ over two years, yielding a minimum mass of $4 ; rm M_{rm J}$; it could be a planet, a brown dwarf, or a low mass star. The hot Jupiter orbital parameters and the presence of the wide orbit companion point towards a high eccentricity migration for the hot Jupiter. Overall, this system will be valuable to understand the atmospheric properties and migration mechanisms of hot Jupiters and will help constrain the formation and evolution models of gas giant exoplanets.
We report the discovery of HAT-P-16b, a transiting extrasolar planet orbiting the V = 10.8 mag F8 dwarf GSC 2792-01700, with a period P = 2.775960 +- 0.000003 d, transit epoch Tc = 2455027.59293 +- 0.00031 (BJD), and transit duration 0.1276 +- 0.0013 d. The host star has a mass of 1.22 +- 0.04 Msun, radius of 1.24 +- 0.05 Rsun, effective temperature 6158 +-80 K, and metallicity [Fe/H] = +0.17 +- 0.08. The planetary companion has a mass of 4.193 +- 0.094 MJ, and radius of 1.289 +- 0.066 RJ yielding a mean density of 2.42 +- 0.35 g/cm3. Comparing these observed characteristics with recent theoretical models, we find that HAT-P-16b is consistent with a 1 Gyr H/He-dominated gas giant planet. HAT-P-16b resides in a sparsely populated region of the mass{radius diagram and has a non-zero eccentricity of e = 0.036 with a significance of 10 sigma.
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We report the discovery of a new transiting extrasolar planet, HAT-P-55b. The planet orbits a V = 13.207 +/- 0.039 sun-like star with a mass of 1.013 +/- 0.037 solar masses, a radius of 1.011 +/- 0.036 solar radii and a metallicity of -0.03 +/- 0.08. The planet itself is a typical hot Jupiter with a period of 3.5852467 +/- 0.0000064 days, a mass of 0.582 +/- 0.056 Jupiter masses and a radius of 1.182 +/- 0.055 Jupiter radii. This discovery adds to the increasing sample of transiting planets with measured bulk densities, which is needed to put constraints on models of planetary structure and formation theories.
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