ABSTRACT We report on the detection and early characterization of a hot Jupiter in a three day orbit around K2-34 (EPIC 212110888), a metal-rich F-type star located in the K2 Cycle 5 field. Our ...follow-up campaign involves precise radial velocity (RV) measurements and high-contrast imaging using multiple facilities. The absence of a bright nearby source in our high-contrast data suggests that the transit-like signals are not due to light variations from such a companion star. Our intensive RV measurements show that K2-34b (EPIC 212110888b) has a mass of , confirming its status as a planet. We also detect the Rossiter-McLaughlin effect for K2-34b and show that the system has a good spin-orbit alignment ( degrees). High-contrast images obtained by the HiCIAO camera on the Subaru 8.2 m telescope reveal a faint companion candidate (CC) ( mag) at a separation of . Follow-up observations are needed to confirm that the CC is physically associated with K2-34. K2-34b appears to be an example of a typical "hot Jupiter," albeit one which can be precisely characterized using a combination of K2 photometry and ground-based follow-up.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted)We report on the discovery and characterization of the transiting planet K2-39b (EPIC 206247743b). With an orbital period of 4.6 days, ...it is the shortest-period planet orbiting a subgiant star known to date. Such planets are rare, with only a handful of known cases. The reason for this is poorly understood but may reflect differences in planet occurrence around the relatively high-mass stars that have been surveyed, or may be the result of tidal destruction of such planets. K2-39 (EPIC 206247743) is an evolved star with a spectroscopically derived stellar radius and mass of ... and ... , respectively, and a very close-in transiting planet, with a/Rlow * = 3.4. Radial velocity (RV) follow-up using the HARPS, FIES, and PFS instruments leads to a planetary mass of ... In combination with a radius measurement of 8.3 + or - 1.1 R+ in circle, this results in a mean planetary density of ... g cm super(-3). We furthermore discover a long-term RV trend, which may be caused by a long-period planet or stellar companion. Because K2-39b has a short orbital period, its existence makes it seem unlikely that tidal destruction is wholly responsible for the differences in planet populations around subgiant and main-sequence stars. Future monitoring of the transits of this system may enable the detection of period decay and constrain the tidal dissipation rates of subgiant stars.
We report the characterization and independent detection of K2-60b, as well as the detection and characterization of K2-107b, two transiting hot gaseous planets from the K2 space mission. We confirm ...the planetary nature of the two systems and determine their fundamental parameters combining the K2 time-series data with FIES@NOT and HARPS-N@TNG spectroscopic observations. K2-60b has a radius of 0.683 0.037 RJup and a mass of 0.426 0.037 MJup and orbits a G4 V star with an orbital period of 3.00267 0.00006 days. K2-107b has a radius of 1.44 0.15 RJup and a mass of 0.84 0.08 MJup and orbits an F9 IV star every 3.31392 0.00002 days. K2-60b is among the few planets at the edge of the so-called "desert" of short-period sub-Jovian planets. K2-107b is a highly inflated Jovian planet orbiting an evolved star about to leave the main sequence.
ABSTRACT We report the discovery of K2-98b (EPIC 211391664b), a transiting Neptune-size planet monitored by the K2 mission during its Campaign 5. We combine the K2 time-series data with ground-based ...photometric and spectroscopic follow-up observations to confirm the planetary nature of the object and derive its mass, radius, and orbital parameters. K2-98b is a warm Neptune-like planet in a 10 day orbit around a V = 12.2 mag F-type star with M = 1.074 0.042 M , R = R , and age of . We derive a planetary mass and radius of Mp = 32.2 8.1 M⊕ and Rp = R⊕. K2-98b joins the relatively small group of Neptune-size planets whose mass and radius have been derived with a precision better than 25%. We estimate that the planet will be engulfed by its host star in ∼3 Gyr, due to the evolution of the latter toward the red giant branch.
TWO HOT JUPITERS FROM K2 CAMPAIGN 4 Johnson, Marshall C.; Gandolfi, Davide; Fridlund, Malcolm ...
The Astronomical journal,
06/2016, Letnik:
151, Številka:
6
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ABSTRACT We confirm the planetary nature of two transiting hot Jupiters discovered by the Kepler spacecraft's K2 extended mission in its Campaign 4, using precise radial velocity measurements from ...FIES@NOT, HARPS-N@TNG, and the coudé spectrograph on the McDonald Observatory 2.7 m telescope. K2-29 b (EPIC 211089792b) transits a K1V star with a period of 3.2589263 0.0000015 days; its orbit is slightly eccentric ( e = 0.084 − 0.023 + 0.032 ). It has a radius of R P = 1.000 − 0.067 + 0.071 RJ and a mass of M P = 0.613 − 0.026 + 0.027 MJ. Its host star exhibits significant rotational variability, and we measure a rotation period of P rot = 10.777 0.031 days. K2-30 b (EPIC 210957318 b) transits a G6V star with a period of 4.098503 0.000011 days. It has a radius of R P = 1.039 − 0.051 + 0.050 RJ and a mass of M P = 0.579 − 0.027 + 0.028 MJ. The star has a low metallicity for a hot Jupiter host, Fe / H = − 0.15 0.05 .
44 Validated Planets from K2 Campaign 10 Livingston, John H.; Endl, Michael; Dai, Fei ...
The Astronomical journal,
08/2018, Letnik:
156, Številka:
2
Journal Article
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We present 44 validated planets from the 10th observing campaign of the NASA K2 mission, as well as high-resolution spectroscopy and speckle imaging follow-up observations. These 44 planets come from ...an initial set of 72 vetted candidates, which we subjected to a validation process incorporating pixel-level analyses, light curve analyses, observational constraints, and statistical false positive probabilities. Our validated planet sample has median values of = , Porb = days, = K, and J = mag. Of particular interest are four ultra-short period planets ( day), 16 planets smaller than 2 , and two planets with large predicted amplitude atmospheric transmission features orbiting infrared-bright stars. We also present 27 planet candidates, most of which are likely to be real and worthy of further observations. Our validated planet sample includes 24 new discoveries and has enhanced the number of currently known super-Earths ( 1-2 ), sub-Neptunes ( 2-4 ), and sub-Saturns ( 4-8 ) orbiting bright stars (J = 8-10 mag) by ∼4%, ∼17%, and ∼11%, respectively.
Context. From a light curve acquired through the K2 space mission, the star K2-111(EPIC 210894022) has been identified as possibly orbited by a transiting planet. Aims. Our aim is to confirm the ...planetary nature of the object and derive its fundamental parameters. Methods. We analyse the light curve variations during the planetary transit using packages developed specifically for exoplanetary transits. Reconnaissance spectroscopy and radial velocity observations have been obtained using three separate telescope and spectrograph combinations. The spectroscopic synthesis package SME has been used to derive the stellar photospheric parameters that were used as input to various stellar evolutionary tracks in order to derive the parameters of the system. The planetary transit was also validated to occur on the assumed host star through adaptive imaging and statistical analysis. Results. The star is found to be located in the background of the Hyades cluster at a distance at least 4 times further away from Earth than the cluster itself. The spectrum and the space velocities of K2-111 strongly suggest it to be a member of the thick disk population. The co-added high-resolution spectra show that that it is a metal poor (Fe/H = − 0.53 ± 0.05 dex) and α-rich somewhat evolved solar-like star of spectral type G3. We find Teff = 5730 ± 50 K, log g⋆ = 4.15 ± 0.1 cgs, and derive a radius of R⋆ = 1.3 ± 0.1 R⊙ and a mass of M⋆ = 0.88 ± 0.02 M⊙. The currently available radial velocity data confirms a super-Earth class planet with a mass of 8.6 ± 3.9 M⊕ and a radius of 1.9 ± 0.2 R⊕. A second more massive object with a period longer than about 120 days is indicated by a long-term radial velocity drift. Conclusions. The radial velocity detection together with the imaging confirms with a high level of significance that the transit signature is caused by a planet orbiting the star K2-111. This planet is also confirmed in the radial velocity data. A second more massive object (planet, brown dwarf, or star) has been detected in the radial velocity signature. With an age of ≳10 Gyr this system is one of the oldest where planets are hitherto detected. Further studies of this planetary system are important since it contains information about the planetary formation process during a very early epoch of the history of our Galaxy.
We present the detection and follow-up observations of planetary candidates around low-mass stars observed by the K2 mission. Based on light-curve analysis, adaptive-optics imaging, and optical ...spectroscopy at low and high resolution (including radial velocity measurements), we validate 16 planets around 12 low-mass stars observed during K2 campaigns 5-10. Among the 16 planets, 12 are newly validated, with orbital periods ranging from 0.96 to 33 days. For one of the planets (K2-151b), we present ground-based transit photometry, allowing us to refine the ephemerides. Combining our K2 M-dwarf planets together with the validated or confirmed planets found previously, we investigate the dependence of planet radius Rp on stellar insolation and metallicity Fe/H. We confirm that for periods P 2 days, planets with a radius are less common than planets with a radius between 1-2 R⊕. We also see a hint of the "radius valley" between 1.5 and 2 R⊕, which has been seen for close-in planets around FGK stars. These features in the radius/period distribution could be attributed to photoevaporation of planetary envelopes by high-energy photons from the host star, as they have for FGK stars. For the M dwarfs, though, the features are not as well defined, and we cannot rule out other explanations such as atmospheric loss from internal planetary heat sources or truncation of the protoplanetary disk. There also appears to be a relation between planet size and metallicity: the few planets larger than about 3 R⊕ are found around the most metal-rich M dwarfs.
We report the discovery of a new ultra-short-period planet and summarize the properties of all such planets for which the mass and radius have been measured. The new planet, K2-131b, was discovered ...in K2 Campaign 10. It has a radius of and orbits a G dwarf with a period of 8.9 hr. Radial velocities obtained with Magellan/PFS and TNG/HARPS-N show evidence for stellar activity along with orbital motion. We determined the planetary mass using two different methods: (1) the "floating chunk offset" method, based only on changes in velocity observed on the same night; and (2) a Gaussian process regression based on both the radial velocity and photometric time series. The results are consistent and lead to a mass measurement of and a mean density of g cm−3.
We report the discovery of EPIC 219388192b, a transiting brown dwarf in a 5.3 day orbit around a member star of Ruprecht 147, the oldest nearby open cluster association, which was photometrically ...monitored by K2 during its Campaign 7. We combine the K2 time-series data with ground-based adaptive optics imaging and high-resolution spectroscopy to rule out false positive scenarios and determine the main parameters of the system. EPIC 219388192b has a radius of RJup and mass of MJup, yielding a mean density of . The host star is nearly a solar twin with mass M , radius R , effective temperature Teff = 5850 85 K, and iron abundance Fe/H = 0.03 0.08 dex. Its age, spectroscopic distance, and reddening are consistent with those of Ruprecht 147, corroborating its cluster membership. EPIC 219388192b is the first mature brown dwarf with precise determinations of mass, radius, and age, and serves as benchmark for evolutionary models in the substellar regime.
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