We report the discovery of HAT-P-15b, a transiting extrasolar planet in the 'period valley,' a relatively sparsely populated period regime of the known extrasolar planets. The host star, GSC ...2883-01687, is a G5 dwarf with V= 12.16. It has a mass of 1.01 ? 0.04 M , radius of 1.08 ? 0.04 R , effective temperature 5568 ? 90 K, and metallicity Fe/H = +0.22 ? 0.08. The planetary companion orbits the star with a period P = 10.863502 ? 0.000027 days, transit epoch Tc = 2454638.56019 ? 0.00048 (BJD), and transit duration 0.2285 ? 0.0015 days. It has a mass of 1.946 ? 0.066 M J and radius of 1.072 ? 0.043 R J yielding a mean density of 1.96 ? 0.22 g cm-3. At an age of 6.8+2.5 --1.6 Gyr, the planet is H/He-dominated and theoretical models require about 2% (10 M {circled plus}) worth of heavy elements to reproduce its measured radius. With an estimated equilibrium temperature of ~820 K during transit, and ~1000 K at occultation, HAT-P-15b is a potential candidate to study moderately cool planetary atmospheres by transmission and occultation spectroscopy.
We report the discovery of two exoplanets transiting high-jitter stars. HAT-P-32b orbits the bright V = 11.289 late-F-early-G dwarf star GSC 3281-00800, with a period P = 2.150008 ? 0.000001 d. The ...stellar and planetary masses and radii depend on the eccentricity of the system, which is poorly constrained due to the high-velocity jitter (~80 m s--1). Assuming a circular orbit, the star has a mass of 1.16 ? 0.04 M and radius of 1.22 ? 0.02 R , while the planet has a mass of 0.860 ? 0.164 M J and a radius of 1.789 ? 0.025 R J. The second planet, HAT-P-33b, orbits the bright V = 11.188 late-F dwarf star GSC 2461-00988, with a period P = 3.474474 ? 0.000001 d. As for HAT-P-32, the stellar and planetary masses and radii of HAT-P-33 depend on the eccentricity, which is poorly constrained due to the high jitter (~50 m s--1). In this case, spectral line bisector spans (BSs) are significantly anti-correlated with the radial velocity residuals, and we are able to use this correlation to reduce the residual rms to ~35 m s--1. We find that the star has a mass of 1.38 ? 0.04 M and a radius of 1.64 ? 0.03 R while the planet has a mass of 0.762 ? 0.101 M J and a radius of 1.686 ? 0.045 R J for an assumed circular orbit. Due to the large BS variations exhibited by both stars we rely on detailed modeling of the photometric light curves to rule out blend scenarios. Both planets are among the largest radii transiting planets discovered to date.
We report the discovery of four relatively massive (2-7 M J) transiting extrasolar planets. HAT-P-20b orbits the moderately bright V = 11.339 K3 dwarf star GSC 1910-00239 on a circular orbit, with a ...period P = 2.875317 ? 0.000004 days, transit epoch Tc = 2455080.92661 ? 0.00021 (BJDUTC), and transit duration 0.0770 ? 0.0008 days. The host star has a mass of 0.76 ? 0.03 M , radius of 0.69 ? 0.02 R , effective temperature 4595 ? 80 K, and metallicity Fe/H = +0.35 ? 0.08. The planetary companion has a mass of 7.246 ? 0.187 M J and a radius of 0.867 ? 0.033 R J yielding a mean density of 13.78 ? 1.50 g cm--3. HAT-P-21b orbits the V = 11.685 G3 dwarf star GSC 3013-01229 on an eccentric (e = 0.228 ? 0.016) orbit, with a period P = 4.124481 ? 0.000007 days, transit epoch Tc = 2454996.41312 ? 0.00069, and transit duration 0.1530 ? 0.0027 days. The host star has a mass of 0.95 ? 0.04 M , radius of 1.10 ? 0.08 R , effective temperature 5588 ? 80 K, and metallicity Fe/H = +0.01 ? 0.08. The planetary companion has a mass of 4.063 ? 0.161 M J and a radius of 1.024 ? 0.092 R J yielding a mean density of 4.68+1.59 -- 0.99 g cm--3. HAT-P-21b is a borderline object between the pM and pL class planets, and the transits occur near apastron. HAT-P-22b orbits the bright V = 9.732 G5 dwarf star HD 233731 on a circular orbit, with a period P = 3.212220 ? 0.000009 days, transit epoch Tc = 2454930.22001 ? 0.00025, and transit duration 0.1196 ? 0.0014 days. The host star has a mass of 0.92 ? 0.03 M , radius of 1.04 ? 0.04 R , effective temperature 5302 ? 80 K, and metallicity Fe/H = +0.24 ? 0.08. The planet has a mass of 2.147 ? 0.061 M J and a compact radius of 1.080 ? 0.058 R J yielding a mean density of 2.11+0.40 -- 0.29 g cm--3. The host star also harbors an M-dwarf companion at a wide separation. Finally, HAT-P-23b orbits the V = 12.432 G0 dwarf star GSC 1632-01396 on a close to circular orbit, with a period P = 1.212884 ? 0.000002 days, transit epoch Tc = 2454852.26464 ? 0.00018, and transit duration 0.0908 ? 0.0007 days. The host star has a mass of 1.13 ? 0.04 M , radius of 1.20 ? 0.07 R , effective temperature 5905 ? 80 K, and metallicity Fe/H = +0.15 ? 0.04. The planetary companion has a mass of 2.090 ? 0.111 M J and a radius of 1.368 ? 0.090 R J yielding a mean density of 1.01 ? 0.18 g cm--3. HAT-P-23b is an inflated and massive hot Jupiter on a very short period orbit, and has one of the shortest characteristic infall times (7.5+2.9 -- 1.8 Myr) before it gets engulfed by the star.
ABSTRACT
We present the discovery of the transiting exoplanets HAT-P-65b and HAT-P-66b, with orbital periods of
and
days, masses of
and
, and inflated radii of
and
, respectively. They orbit ...moderately bright (
and
) stars of mass
and
. The stars are at the main-sequence turnoff. While it is well known that the radii of close-in giant planets are correlated with their equilibrium temperatures, whether or not the radii of planets increase in time as their hosts evolve and become more luminous is an open question. Looking at the broader sample of well-characterized close-in transiting giant planets, we find that there is a statistically significant correlation between planetary radii and the fractional ages of their host stars, with a false-alarm probability of only 0.0041%. We find that the correlation between the radii of planets and the fractional ages of their hosts is fully explained by the known correlation between planetary radii and their present-day equilibrium temperatures; however, if the zero-age main-sequence equilibrium temperature is used in place of the present-day equilibrium temperature, then a correlation with age must also be included to explain the planetary radii. This suggests that, after contracting during the pre-main-sequence, close-in giant planets are reinflated over time due to the increasing level of irradiation received from their host stars. Prior theoretical work indicates that such a dynamic response to irradiation requires a significant fraction of the incident energy to be deposited deep within the planetary interiors.
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 days, transit epoch Tc = 2455456.46561 ...? 0.00037 (BJD), and transit duration 0.0887 ? 0.0015 days. The host star has a mass of 1.24 ? 0.04 M , radius of 1.21 ? 0.05 R , effective temperature of 6304 ? 88 K, and metallicity Fe/H = +0.13 ? 0.08. The planetary companion has a mass of 0.711 ? 0.028 M J and radius of 1.340 ? 0.065 R J 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 Delta *l = 735 ? 90 between the sky projections of the planet's orbit normal and the star's 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 T eff 6250 K.
We report the discovery of HAT-P-26b, a transiting extrasolar planet orbiting the moderately bright V = 11.744 K1 dwarf star GSC 0320--01027, with a period P = 4.234516 ? 0.000015 days, transit epoch ...Tc = 2455304.65122 ? 0.00035 (BJD; Barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time (UTC)), and transit duration 0.1023 ? 0.0010 days. The host star has a mass of 0.82 ? 0.03 M , radius of 0.79+0.10 --0.04 R , effective temperature 5079 ? 88 K, and metallicity Fe/H = -0.04 ? 0.08. The planetary companion has a mass of 0.059 ? 0.007 M J, and radius of 0.565+0.072 --0.032 R J yielding a mean density of 0.40 ? 0.10 g cm-3. HAT-P-26b is the fourth Neptune-mass transiting planet discovered to date. It has a mass that is comparable to those of Neptune and Uranus, and slightly smaller than those of the other transiting Super-Neptunes, but a radius that is ~65% larger than those of Neptune and Uranus, and also larger than those of the other transiting Super-Neptunes. HAT-P-26b is consistent with theoretical models of an irradiated Neptune-mass planet with a 10 M {circled plus} heavy element core that comprises 50% of its mass with the remainder contained in a significant hydrogen-helium envelope, though the exact composition is uncertain as there are significant differences between various theoretical models at the Neptune-mass regime. The equatorial declination of the star makes it easily accessible to both Northern and Southern ground-based facilities for follow-up observations.
Abstract
We report the discovery of HAT-P-67b, which is a hot-Saturn transiting a rapidly rotating F-subgiant. HAT-P-67b has a radius of
, and orbites a
,
host star in a ∼4.81 day period orbit. We ...place an upper limit on the mass of the planet via radial velocity measurements to be
, and a lower limit of
by limitations on Roche lobe overflow. Despite being a subgiant, the host star still exhibits relatively rapid rotation, with a projected rotational velocity of
, which makes it difficult to precisely determine the mass of the planet using radial velocities. We validated HAT-P-67b via two Doppler tomographic detections of the planetary transit, which eliminate potential eclipsing binary blend scenarios. The Doppler tomographic observations also confirm that HAT-P-67b has an orbit that is aligned to within 12°, in projection, with the spin of its host star. HAT-P-67b receives strong UV irradiation and is among one of the lowest density planets known, which makes it a good candidate for future UV transit observations in the search for an extended hydrogen exosphere.
We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiting a V = 13.46 mag G star. HATS-4b has a period of P approximately 2.5167 days, mass of M sub(p) approximately ...1.32 M sub(Jup), radius of R sub(p) approximately 1.02 R sub(Jup), and density of rho sub(p) = 1.55 + or - 0.16 g cm super(-3) approximately 1.24 rho sub(Jup). The host star has a mass of 1.00 M sub(odot), a radius of 0.92 R sub(odot), and a very high metallicity Fe/H = 0.43 + or - 0.08. HATS-4b is among the densest known planets with masses between 1 and 2 M sub(J) and is thus likely to have a significant content of heavy elements of the order of 75 M sub(+ in circle). In this paper we present the data reduction, radial velocity measurements, and stellar classification techniques adopted by the HATSouth survey for the CORALIE spectrograph. We also detail a technique for simultaneously estimating v sin i and macroturbulence using high resolution spectra.
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