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Register a new userK2-114b and K2-115b: Two Transiting Warm Jupiters
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We report the first results from a search for transiting warm Jupiter exoplanets - gas giant planets receiving stellar irradiation below about $10^8$ erg s$^{-1}$ cm$^{-2}$, equivalent to orbital periods beyond about 10 days around Sun-like stars. We have discovered two transiting warm Jupiter exoplanets initially identified as transiting candidates in ${it K2}$ photometry. K2-114b has a mass of $1.85^{+0.23}_{-0.22} M_J$, a radius of $0.942^{+0.032}_{-0.020} R_J$, and an orbital period of 11.4 days. K2-115b has a mass of $0.84^{+0.18}_{-0.20} M_J$, a radius of $1.115^{+0.057}_{-0.061} R_J$, and an orbital period of 20.3 days. Both planets are among the longest period transiting gas giant planets with a measured mass, and they are orbiting relatively old host stars. Both planets are not inflated as their radii are consistent with theoretical expectations. Their position in the planet radius - stellar irradiation diagram is consistent with the scenario where the radius - irradiation correlation levels off below about 10$^8$ erg s$^{-1}$ cm$^{-2}$, suggesting that for warm Jupiters the stellar irradiation does not play a significant role in determining the planet radius. We also report our identification of another ${it K2}$ transiting warm Jupiter candidate, EPIC 212504617, as a false positive.
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We report the discovery from K2 of two transiting hot Jupiter systems. K2-295 (observed in Campaign 8) is a K5 dwarf which hosts a planet slightly smaller than Jupiter, orbiting with a period of 4.0 d. We have made an independent discovery of K2-237 b (Campaign 11), which orbits an F6 dwarf every 2.2 d and has an inflated radius 50 - 60 per cent larger than that of Jupiter. We use high-precision radial velocity measurements, obtained using the HARPS and FIES spectrographs, to measure the planetary masses. We find that K2-295 b has a similar mass to Saturn, while K2-237 b is a little more massive than Jupiter.
We confirm the planetary nature of two transiting hot Jupiters discovered by the Kepler spacecrafts K2 extended mission in its Campaign 4, using precise radial velocity measurements from FIES@NOT, HARPS-N@TNG, and the coude spectrograph on the McDonald Observatory 2.7 m telescope. K2-29 b (EPIC 211089792 b) transits a K1V star with a period of $3.2589263pm0.0000015$ days; its orbit is slightly eccentric ($e=0.084_{-0.023}^{+0.032}$). It has a radius of $R_P=1.000_{-0.067}^{+0.071}$ $R_J$ and a mass of $M_P=0.613_{-0.026}^{+0.027}$ $M_J$. Its host star exhibits significant rotational variability, and we measure a rotation period of $P_{mathrm{rot}}=10.777 pm 0.031$ days. K2-30 b (EPIC 210957318 b) transits a G6V star with a period of $4.098503pm0.000011$ days. It has a radius of $R_P=1.039_{-0.051}^{+0.050}$ $R_J$ and a mass of $M_P=0.579_{-0.027}^{+0.028}$ $M_J$. The star has a low metallicity for a hot Jupiter host, $[mathrm{Fe}/mathrm{H}]=-0.15 pm 0.05$.
We report the discovery of two hot Jupiters orbiting the stars EPIC229426032 and EPIC246067459. We used photometric data from Campaign 11 and 12 of the Kepler K2 Mission and radial velocity data obtained using the HARPS, FEROS, and CORALIE spectrographs. EPIC229426032 b and EPIC246067459 b have masses of $1.60^{+0.11}_{-0.11}$ and $0.86^{+0.13}_{-0.12},M_{mathrm{Jup}}$, radii of $1.65^{+0.07}_{-0.08}$ and $1.30^{+0.15}_{-0.14},R{_mathrm{Jup}}$, and are orbiting their host stars in 2.18 and 3.20-day orbits, respectively. The large radius of EPIC229426032 b leads us to conclude that this candidate corresponds to a highly inflated hot Jupiter. EPIC2460674559 b has a radius consistent with theoretical models, considering the high incident flux falling on the planet. We consider EPIC229426032 b to be a excellent system for follow-up studies, since not only is it very inflated, but it also orbits a relatively bright star ($V = 11.6$).
We report the discovery of K2-287b, a Saturn mass planet orbiting a G-dwarf with a period of $P approx 15$ days. First uncovered as a candidate using K2 campaign 15 data, follow-up photometry and spectroscopy were used to determine a mass of $M_P = 0.317 pm 0.026$ $M_J$, radius $R_P = 0.833 pm 0.013$ $R_J$, period $P = 14.893291 pm 0.000025$ days and eccentricity $e = 0.476 pm 0.026$. The host star is a metal-rich $V=11.410 pm 0.129$ mag G dwarf for which we estimate a mass $M_* = 1.056$ $M_odot$, radius $R_* = 1.07 pm 0.01$ $R_odot$, metallicity [Fe/H] = $0.20 pm 0.05$ and $T_{eff} = 5673 pm 75$ K. This warm eccentric planet with a time-averaged equilibrium temperature of $T_{eq} approx 800$ K adds to the small sample of giant planets orbiting nearby stars whose structure is not expected to be affected by stellar irradiation. Follow-up studies on the K2-287 system could help in constraining theories of migration of planets in close-in orbits.
We report the discovery and confirmation of two sub-Saturn planets orbiting a bright (V = 11.3), metal-rich ([Fe/H] = 0.42 $pm$ 0.04 dex) G3 dwarf in the K2 Campaign 2 field. The planets are 5.68 $pm$ 0.56 Earth-radii and 7.82 $pm$ 0.72 Earth-radii and have orbital periods of 20.8851 $pm$ 0.0003 d and 42.3633$pm$0.0006 d, near to the 2:1 mean-motion resonance. We obtained 32 radial velocities (RVs) with Keck/HIRES and detected the reflex motion due to EPIC-203771098b and c. These planets have masses of 21.0 $pm$ 5.4 Earth-masses and 27.0 $pm$ 6.9 Earth-masses, respectively. With low densities of 0.63 $pm$ 0.25 g/cc and 0.31 $pm$ 0.12 g/cc, respectively, the planets require thick envelopes of H/He to explain their large sizes and low masses. Interior structure models predict that the planets have fairly massive cores of 17.6 $pm$ 4.3 Earth-masses and 16.1 $pm$ 4.2 Earth-masses, respectively. They may have formed exterior to their present locations, accreted their H/He envelopes at large orbital distances, and migrated in as a resonant pair. The proximity to resonance, large transit depths, and host star brightness offer rich opportunities for TTV follow-up. Finally, the low surface gravities of the EPIC-203771098 planets make them favorable targets for transmission spectroscopy by HST, Spitzer, and JWST.
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