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.
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.
We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 + or - 0.000019 days, transit epoch Tc = ...2455176.85173 + or - 0.00047 (BJD-barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time, UTC), and transit duration 0.1174 + or - 0.0017 days. The host star has amass of 1.01 + or - 0.03 M radius of (ProQuest: Formulae and/or non-USASCII text omitted) R effective temperature 5500 + or - 80 K, and metallicity Fe/H = +0.31 + or - 0.08. The planetary companion has a mass of 0.567 + or - 0.022 M sub(J) and radius of (ProQuest: Formulae and/or non-USASCII text omitted) R sub(J) yielding a mean density of 0.42 + or - 0.07 g cm super(-3).
We report the discovery of HAT-P-27b, an exoplanet transiting the moderately bright G8 dwarf star GSC 0333-00351 (V = 12.214). The orbital period is 3.039586 ? 0.000012 days, the reference epoch of ...transit is 2455186.01879 ? 0.00054 (BJD), and the transit duration is 0.0705 ? 0.0019 days. The host star with its effective temperature 5300 ? 90 K is somewhat cooler than the Sun and is more metal-rich with a metallicity of +0.29 ? 0.10. Its mass is 0.94 ? 0.04 M and radius is 0.90+0.05 -- 0.04 R . For the planetary companion we determine a mass of 0.660 ? 0.033 M J and radius of 1.038+0.077 -- 0.058 R J. For the 30 known transiting exoplanets between 0.3 M J and 0.8 M J, a negative correlation between host star metallicity and planetary radius and an additional dependence of planetary radius on equilibrium temperature are confirmed at a high level of statistical significance.
We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting the moderately bright V = 11.818 F8 dwarf star GSC 0774--01441, with a period P = 3.3552464 ? 0.0000071 days, transit ...epoch Tc = 2455216.97669 ? 0.00024 (BJD)11, and transit duration 3.653 ? 0.025 hr. The host star has a mass of 1.191 ? 0.042 M , radius of 1.317 ? 0.068 R , effective temperature 6373 ? 80 K, and a low metallicity of Fe/H = -0.16 ? 0.08. The planetary companion has a mass of 0.681 ? 0.031 M J and radius of 1.243 ? 0.072 R J yielding a mean density of 0.439 ? 0.069 g cm-3. By repeating our global fits with different parameter sets, we have performed a critical investigation of the fitting techniques used for previous Hungarian-made Automated Telescope planetary discoveries. We find that the system properties are robust against the choice of priors. The effects of fixed versus fitted limb darkening are also examined. HAT-P-24b probably maintains a small eccentricity of e = 0.052+0.022 --0.017, which is accepted over the circular orbit model with false alarm probability 5.8%. In the absence of eccentricity pumping, this result suggests that HAT-P-24b experiences less tidal dissipation than Jupiter. Due to relatively rapid stellar rotation, we estimate that HAT-P-24b should exhibit one of the largest known Rossiter-McLaughlin effect amplitudes for an exoplanet ( Delta *DV RM 95 m s--1) and thus a precise measurement of the sky-projected spin-orbit alignment should be possible.
We report the discovery of two new transiting extrasolar planets. HAT-P-18b orbits the V = 12.759 K2 dwarf star GSC 2594--00646, with a period P = 5.508023 ? 0.000006 days, transit epoch Tc = ...2454715.02174 ? 0.00020 (BJD), and transit duration 0.1131 ? 0.0009 days. The host star has a mass of 0.77 ? 0.03 M , radius of 0.75 ? 0.04 R , effective temperature 4803 ? 80 K, and metallicity Fe/H = +0.10 ? 0.08. The planetary companion has a mass of 0.197 ? 0.013 M J and radius of 0.995 ? 0.052 R J, yielding a mean density of 0.25 ? 0.04 g cm--3. HAT-P-19b orbits the V = 12.901 K1 dwarf star GSC 2283--00589, with a period P = 4.008778 ? 0.000006 days, transit epoch Tc = 2455091.53417 ? 0.00034 (BJD), and transit duration 0.1182 ? 0.0014 days. The host star has a mass of 0.84 ? 0.04 M , radius of 0.82 ? 0.05 R , effective temperature 4990 ? 130 K, and metallicity Fe/H = +0.23 ? 0.08. The planetary companion has a mass of 0.292 ? 0.018 M J and radius of 1.132 ? 0.072 R J, yielding a mean density of 0.25 ? 0.04 g cm--3. The radial velocity residuals for HAT-P-19 exhibit a linear trend in time, which indicates the presence of a third body in the system. Comparing these observations with theoretical models, we find that HAT-P-18b and HAT-P-19b are each consistent with a hydrogen-helium-dominated gas giant planet with negligible core mass. HAT-P-18b and HAT-P-19b join HAT-P-12b and WASP-21b in an emerging group of low-density Saturn-mass planets, with negligible inferred core masses. However, unlike HAT-P-12b and WASP-21b, both HAT-P-18b and HAT-P-19b orbit stars with super-solar metallicity. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This ...mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7σ̃ confidence level, using a low-background, 14.6-kilogram CsINa scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the standard model for this process, were observed in high signal-to-background conditions. Improved constraints on nonstandard neutrino interactions with quarks are derived from this initial data set.
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