Abstract
We report the discovery of HATS-70b, a transiting brown dwarf at the deuterium burning limit. HATS-70b has a mass of
and a radius of
, residing in a close-in orbit with a period of
days. The ...host star is a
A star rotating at
, enabling us to characterize the spectroscopic transit of the brown dwarf via Doppler tomography. We find that HATS-70b, like other massive planets and brown dwarfs previously sampled, orbits in a low projected-obliquity orbit with
. The low obliquities of these systems is surprising given all brown dwarf and massive planets with obliquities measured orbit stars hotter than the Kraft break. This trend is tentatively inconsistent with dynamically chaotic migration for systems with massive companions, though the stronger tidal influence of these companions makes it difficult to draw conclusions on the primordial obliquity distribution of this population. We also introduce a modeling scheme for planets around rapidly rotating stars, accounting for the influence of gravity darkening on the derived stellar and planetary parameters.
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.
Abstract
We report the discovery of 10 transiting extrasolar planets by the HATSouth survey. The planets range in mass from the super-Neptune HATS-62b, with
, to the super-Jupiter HATS-66b, with
, ...and in size from the Saturn HATS-69b, with
, to the inflated Jupiter HATS-67b, with
. The planets have orbital periods between
days (HATS-67b) and
days (HATS-61b). The hosts are dwarf stars with masses ranging from
(HATS-69) to
(HATS-64) and have apparent magnitudes between
mag (HATS-68) and
mag (HATS-66). The super-Neptune HATS-62b is the least massive planet discovered to date with a radius larger than Jupiter. Based largely on the
Gaia
DR2 distances and broadband photometry, we identify three systems (HATS-62, HATS-64, and HATS-65) as having possible unresolved binary star companions. We discuss in detail our methods for incorporating the
Gaia
DR2 observations into our modeling of the system parameters and into our blend analysis procedures.
We report on the discovery of HAT-P-11b, the smallest radius transiting extrasolar planet (TEP) discovered from the ground, and the first hot Neptune discovered to date by transit searches. HAT-P-11b ...orbits the bright (V = 9.587) and metal rich (Fe/H = +0.31 +- 0.05) K4 dwarf star GSC 03561-02092 with P = 4.8878162 +- 0.0000071 days and produces a transit signal with depth of 4.2 mmag, the shallowest found by transit searches that is due to a confirmed planet. We present a global analysis of the available photometric and radial velocity (RV) data that result in stellar and planetary parameters, with simultaneous treatment of systematic variations. The planet, like its near-twin GJ 436b, is somewhat larger than Neptune (17 M{sub +}, 3.8 R{sub +}) both in mass M{sub p} = 0.081 +- 0.009 M{sub J}(25.8 +- 2.9 M{sub +}) and radius R{sub p} = 0.422 +- 0.014 R{sub J}(4.73 +- 0.16 R{sub +}). HAT-P-11b orbits in an eccentric orbit with e = 0.198 +- 0.046 and omega = 355.{sup 0}2 +- 17.{sup 0}3, causing a reflex motion of its parent star with amplitude 11.6 +- 1.2 m s{sup -1}, a challenging detection due to the high level of chromospheric activity of the parent star. Our ephemeris for the transit events is T{sub c} = 2454605.89132 +- 0.00032 (BJD), with duration 0.0957 +- 0.0012 days, and secondary eclipse epoch of 2454608.96 +- 0.15 days (BJD). The basic stellar parameters of the host star are M{sub *} = 0.809{sup +0.020}{sub -0.027} M{sub sun}, R{sub *} = 0.752 +- 0.021 R{sub sun}, and T{sub eff*} = 4780 +- 50 K. Importantly, HAT-P-11 will lie on one of the detectors of the forthcoming Kepler mission; this should make possible fruitful investigations of the detailed physical characteristic of both the planet and its parent star at unprecedented precision. We discuss an interesting constraint on the eccentricity of the system by the transit light curve and stellar parameters. This will be particularly useful for eccentric TEPs with low-amplitude RV variations in Kepler's field. We also present a blend analysis, that for the first time treats the case of a blended transiting hot Jupiter mimicking a transiting hot Neptune, and proves that HAT-P-11b is not such a blend.
Abstract
We report the discovery of two transiting Neptunes by the HATSouth survey. The planet HATS-37Ab has a mass of
(31.5 ± 13.4
M
⊕
) and a radius of
, and is on a
day orbit around a
mag,
star ...with a radius of
. We also present evidence that the star HATS-37A has an unresolved stellar companion HATS-37B, with a photometrically estimated mass of
. The planet HATS-38b has a mass of
(23.5 ± 3.5
M
⊕
) and a radius of
, and is on a
day orbit around a
mag,
star with a radius of
. Both systems appear to be old, with isochrone-based ages of
Gyr, and
Gyr, respectively. Both HATS-37Ab and HATS-38b lie in the Neptune desert and are thus examples of a population with a low occurrence rate. They are also among the lowest-mass planets found from ground-based wide-field surveys 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.
We report on the discovery of HAT-P-12b, a transiting extrasolar planet orbiting the moderately bright V 12.8 K4 dwarf GSC 03033 - 00706, with a period P = 3.2130598 +/- 0.0000021 d, transit epoch Tc ...= 2454419.19556 +/- 0.00020 (BJD), and transit duration 0.0974 +/- 0.0006 d. The host star has a mass of 0.73 +/- 0.02 M, radius of 0.70+0.02 -0.01 R, effective temperature 4650 +/- 60 K, and metallicity Fe/H = -0.29 +/- 0.05. We find a slight correlation between the observed spectral line bisector spans and the radial velocity, so we consider, and rule out, various blend configurations including a blend with a background eclipsing binary, and hierarchical triple systems where the eclipsing body is a star or a planet. We conclude that a model consisting of a single star with a transiting planet best fits the observations, and show that a likely explanation for the apparent correlation is contamination from scattered moonlight. Based on this model, the planetary companion has a mass of 0.211 +/- 0.012 M J and radius of 0.959+0.029 -0.021 R J yielding a mean density of 0.295 +/- 0.025 g cm-3. Comparing these observations with recent theoretical models, we find that HAT-P-12b is consistent with a ~1-4.5 Gyr, mildly irradiated, H/He-dominated planet with a core mass MC 10 M {circled plus}. HAT-P-12b is thus the least massive H/He-dominated gas giant planet found to date. This record was previously held by Saturn.
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.
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