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Register a new userEPIC 228735255b - An eccentric 6.57 day transiting hot Jupiter in Virgo
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We present the discovery of EPIC 228735255b, a P= 6.57 days Jupiter-mass (M$_P$=1.019$pm$0.070 M$_{Jup}$) planet transiting a V=12.5 (G5-spectral type) star in an eccentric orbit (e=$0.120^{+0.056}_{-0.046}$) detected using a combination of K2 photometry and ground-based observations. With a radius of 1.095$pm$0.018R$_{Jup}$ the planet has a bulk density of 0.726$pm$0.062$rho_{Jup}$. The host star has a [Fe/H] of 0.12$pm$0.045, and from the K2 light curve we find a rotation period for the star of 16.3$pm$0.1 days. This discovery is the 9th hot Jupiter from K2 and highlights K2s ability to detect transiting giant planets at periods slightly longer than traditional, ground-based surveys. This planet is slightly inflated, but much less than others with similar incident fluxes. These are of interest for investigating the inflation mechanism of hot Jupiters.
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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.
We study the Kepler object Kepler-432, an evolved star ascending the red giant branch. By deriving precise radial velocities from multi-epoch high-resolution spectra of Kepler-432 taken with the CAFE spectrograph at the 2.2m telescope of Calar Alto Observatory and the FIES spectrograph at the Nordic Optical Telescope of Roque de Los Muchachos Observatory, we confirm the planetary nature of the object Kepler-432 b, which has a transit period of 52 days. We find a planetary mass of Mp=5.84 +- 0.05 Mjup and a high eccentricity of e=0.478 +- 0.004. With a semi-major axis of a=0.303 +- 0.007 AU, Kepler-432 b is the first bona fide warm Jupiter detected to transit a giant star. We also find a radial velocity linear trend of 0.44 +- 0.04 m s$^{-1}$ d$^{-1}$, which suggests the presence of a third object in the system. Current models of planetary evolution in the post-main-sequence phase predict that Kepler-432 b will be most likely engulfed by its host star before the latter reaches the tip of the red giant branch.
We report the discovery of the first hot Jupiter in the Hyades open cluster. HD 285507b orbits a V=10.47 K4.5V dwarf ($M_* = 0.734 M_odot$; $R_* = 0.656 R_odot$) in a slightly eccentric ($e = 0.086^{+0.018}_{-0.019}$) orbit with a period of $6.0881^{+0.0019}_{-0.0018}$ days. The induced stellar radial velocity corresponds to a minimum companion mass of $M_{rm p} sin{i} = 0.917 pm 0.033 M_{rm Jup}$. Line bisector spans and stellar activity measures show no correlation with orbital phase, and the radial velocity amplitude is independent of wavelength, supporting the conclusion that the variations are caused by a planetary companion. Follow-up photometry indicates with high confidence that the planet does not transit. HD 285507b joins a small but growing list of planets in open clusters, and its existence lends support to a planet formation scenario in which a high stellar space density does not inhibit giant planet formation and migration. We calculate the circularization timescale for HD 285507b to be larger than the age of the Hyades, which may indicate that this planets non-zero eccentricity is the result of migration via interactions with a third body. We also demonstrate a significant difference between the eccentricity distributions of hot Jupiters that have had time to tidally circularize and those that have not, which we interpret as evidence against Type II migration in the final stages of hot Jupiter formation. Finally, the dependence of the circularization timescale on the planetary tidal quality factor, $Q_{rm p}$, allows us to constrain the average value for hot Jupiters to be $log{Q_{rm p}} = 6.14^{+0.41}_{-0.25}$.
We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host ($T_{eff}=3916^{+71}_{-63}~K$) in a P=2.674d orbit discovered as part of the Next Generation Transit Survey (NGTS). The planet has a mass of $0.812^{+0.066}_{-0.075}~M_{J}$, making it the most massive planet ever discovered transiting an M-dwarf. The radius of the planet is $1.33^{+0.61}_{-0.33}~R_{J}$. Since the transit is grazing, we determine this radius by modelling the data and placing a prior on the density from the population of known gas giant planets. NGTS-1b is the third transiting giant planet found around an M-dwarf, reinforcing the notion that close-in gas giants can form and migrate similar to the known population of hot Jupiters around solar type stars. The host star shows no signs of activity, and the kinematics hint at the star being from the thick disk population. With a deep (2.5%) transit around a $K=11.9$ host, NGTS-1b will be a strong candidate to probe giant planet composition around M-dwarfs via JWST transmission spectroscopy.
We report the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting a mildly evolved host star. We identified the initial transit signal in the KELT-North survey data and established the planetary nature of the companion through precise follow-up photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the $V = 10.64$ host, TYC 2619-1057-1, has $T_{rm eff} = 6278 pm 51$ K, $log{g_star} = 3.89^{+0.054}_{-0.051}$, and [Fe/H] = $0.19^{+0.083}_{-0.085}$, with an inferred mass $M_{star} = 1.59^{+0.071}_{-0.091} M_odot$ and radius $R_star = 2.37 pm 0.18 R_odot$. The planetary companion has $M_{rm P} = 0.95 pm 0.14 M_{rm J}$, $R_{rm P} = 1.79^{+0.18}_{-0.17} R_{rm J}$, $log{g_{rm P}} = 2.87^{+0.097}_{-0.098}$, and density $rho_{rm P} = 0.21^{+0.075}_{-0.054}$ g cm$^{-3}$, making it one of the most inflated giant planets known. The time of inferior conjunction in ${rm BJD_{TDB}}$ is $2457088.692055 pm 0.0009$ and the period is $P = 5.0316144 pm 0.0000306$ days. Despite the relatively large separation of $sim0.07$ AU implied by its $sim 5.03$-day orbital period, KELT-12b receives significant flux of $2.93^{+0.33}_{-0.30} times 10^9$ erg s$^{-1}$ cm$^{-2}$ from its host. We compare the radii and insolations of transiting gas-giant planets around hot ($T_{rm eff} geq 6250$ K) and cool stars, noting that the observed paucity of known transiting giants around hot stars with low insolation is likely due to selection effects. We underscore the significance of long-term ground-based monitoring of hot stars and space-based targeting of hot stars with the Transiting Exoplanet Survey Satellite (TESS) to search for inflated giants in longer-period orbits.
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