We present the first detections by the NASA K2 mission of oscillations in solar-type stars, using short-cadence data collected during K2 Campaign 1 (C1). We understand the asteroseismic detection ...thresholds for C1-like levels of photometric performance, and we can detect oscillations in subgiants having dominant oscillation frequencies around 1000 μHz. Changes to the operation of the fine-guidance sensors are expected to give significant improvements in the high-frequency performance from C3 onwards. A reduction in the excess high-frequency noise by a factor of 2.5 in amplitude would bring main-sequence stars with dominant oscillation frequencies as high as ≃2500 μHz into play as potential asteroseismic targets for K2.
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.
Ultra-short period (USP) planets are a class of exoplanets with periods shorter than one day. The origin of this sub-population of planets is still unclear, with different formation scenarios highly ...dependent on the composition of the USP planets. A better understanding of this class of exoplanets will, therefore, require an increase in the sample of such planets that have accurate and precise masses and radii, which also includes estimates of the level of irradiation and information about possible companions. Here we report a detailed characterization of a USP planet around the solar-type star HD 80653 ≡EP 251279430 using the K2 light curve and 108 precise radial velocities obtained with the HARPS-N spectrograph, installed on the Telescopio Nazionale
Galileo
. From the K2 C16 data, we found one super-Earth planet (
R
b
= 1.613 ± 0.071
R
⊕
) transiting the star on a short-period orbit (
P
b
= 0.719573 ± 0.000021 d). From our radial velocity measurements, we constrained the mass of HD 80653 b to
M
b
= 5.60 ± 0.43
M
⊕
. We also detected a clear long-term trend in the radial velocity data. We derived the fundamental stellar parameters and determined a radius of
R
⋆
= 1.22 ± 0.01
R
⊙
and mass of
M
⋆
= 1.18 ± 0.04
M
⊙
, suggesting that HD 80653 has an age of 2.7 ± 1.2 Gyr. The bulk density (
ρ
b
= 7.4 ± 1.1 g cm
−3
) of the planet is consistent with an Earth-like composition of rock and iron with no thick atmosphere. Our analysis of the K2 photometry also suggests hints of a shallow secondary eclipse with a depth of 8.1 ± 3.7 ppm. Flux variations along the orbital phase are consistent with zero. The most important contribution might come from the day-side thermal emission from the surface of the planet at
T
~ 3480 K.
Heartbeat stars are eccentric (e > 0.2) ellipsoidal variables whose light curves resemble a cardiogram. We present the observations and corresponding model of KIC 3749404, a highly eccentric (e = ...0.66), short period (P = 20.3 d) heartbeat star with tidally induced pulsations. A binary star model was created using phoebe, which we modified to include tidally induced pulsations and Doppler boosting. The morphology of the photometric periastron variation (heartbeat) depends strongly on the eccentricity, inclination and argument of periastron. We show that the inclusion of tidally induced pulsations in the model significantly changes the parameter values, specifically the inclination and those parameters dependent on it. Furthermore, we determine the rate of apsidal advance by modelling the periastron variation at the beginning and end of the 4-yr Kepler data set and dividing by the elapsed time. We compare the model with the theoretical expectations for classical and general relativistic apsidal motion and find the observed rate to be two orders of magnitude greater than the theoretical rate. We find that the observed rate cannot be explained by tidally induced pulsations alone and consequently hypothesize the presence of a third body in the system.
ABSTRACT
We report on precise Doppler measurements of L231-32 (TOI-270), a nearby M dwarf (d = 22 pc, M⋆ = 0.39 M⊙, R⋆ = 0.38 R⊙), which hosts three transiting planets that were recently discovered ...using data from the Transiting Exoplanet Survey Satellite (TESS). The three planets are 1.2, 2.4, and 2.1 times the size of Earth and have orbital periods of 3.4, 5.7, and 11.4 d. We obtained 29 high-resolution optical spectra with the newly commissioned Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) and 58 spectra using the High Accuracy Radial velocity Planet Searcher (HARPS). From these observations, we find the masses of the planets to be 1.58 ± 0.26, 6.15 ± 0.37, and 4.78 ± 0.43 M⊕, respectively. The combination of radius and mass measurements suggests that the innermost planet has a rocky composition similar to that of Earth, while the outer two planets have lower densities. Thus, the inner planet and the outer planets are on opposite sides of the ‘radius valley’ – a region in the radius-period diagram with relatively few members – which has been interpreted as a consequence of atmospheric photoevaporation. We place these findings into the context of other small close-in planets orbiting M dwarf stars, and use support vector machines to determine the location and slope of the M dwarf (Teff < 4000 K) radius valley as a function of orbital period. We compare the location of the M dwarf radius valley to the radius valley observed for FGK stars, and find that its location is a good match to photoevaporation and core-powered mass-loss models. Finally, we show that planets below the M dwarf radius valley have compositions consistent with stripped rocky cores, whereas most planets above have a lower density consistent with the presence of a H-He atmosphere.
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 +/- 0.000010 days, with transit epoch Tc = 2454779.92979 +/- 0.00038 (BJD) and duration 0.1345 +/- 0.0017 days. The outer planet HAT-P-13c orbits the star every P 2 = 428.5 +/- 3.0 days with a nominal transit center (assuming zero impact parameter) of T 2c = 2454870.4 +/- 1.8 (BJD) or time of periastron passage T 2,peri = 2454890.05 +/- 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+0.05 -0.10 M, radius of 1.56 +/- 0.08 R, effective temperature of 5653 +/- 90 K, and is rather metal-rich with Fe/H = +0.41 +/- 0.08. The inner planetary companion has a mass of 0.853+0.029 -0.046 M J, and radius of 1.281 +/- 0.079 R J, yielding a mean density of 0.498+0.103 -0.069 g cm-3. The outer companion has m 2sin i 2 = 15.2 +/- 1.0 M J, and orbits on a highly eccentric orbit of e 2 = 0.691 +/- 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.
Abstract
We report the joint WASP/KELT discovery of WASP-167b/KELT-13b, a transiting hot Jupiter with a 2.02-d orbit around a V = 10.5, F1V star with Fe/H = 0.1 ± 0.1. The 1.5 R
Jup planet was ...confirmed by Doppler tomography of the stellar line profiles during transit. We place a limit of <8 M
Jup on its mass. The planet is in a retrograde orbit with a sky-projected spin–orbit angle of λ = −165° ± 5°. This is in agreement with the known tendency for orbits around hotter stars to be more likely to be misaligned. WASP-167/KELT-13 is one of the few systems where the stellar rotation period is less than the planetary orbital period. We find evidence of non-radial stellar pulsations in the host star, making it a δ-Scuti or γ-Dor variable. The similarity to WASP-33, a previously known hot-Jupiter host with pulsations, adds to the suggestion that close-in planets might be able to excite stellar pulsations.
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.
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