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Ten Multi-planet Systems from K2 Campaigns 1 & 2 and the Masses of Two Hot Super-Earths
[1511.09213] Ten Multi-planet Systems from K2 Campaigns 1 & 2 and the Masses of Two Hot Super-Earths
http://arxiv.org/pdf/1511.09213v1.pdf
Evan Sinukoff, Andrew W. Howard, Erik A. Petigura, Joshua E. Schlieder, Ian J. M. Crossfield, David R. Ciardi, Benjamin J. Fulton, Howard Isaacson, Kimberly M. Aller, Christoph Baranec, Charles A. Beichman, Brad M. S. Hansen, Heather A. Knutson, Nicholas M. Law, Michael C. Liu, Reed Riddle
(Submitted on 30 Nov 2015)
We present a catalog of 10 multi-planet systems from Campaigns 1 and 2 of the K2 mission. We report the sizes and orbits of 24 planets split between six 2-planet systems and four 3-planet systems. These planets stem from a systematic search of the K2 photometry for all dwarf stars observed by K2 in these fields. We precisely characterized the host stars with adaptive optics imaging and analysis of high-resolution optical spectra from Keck/HIRES and medium-resolution spectra from IRTF/SpeX. The planets are mostly smaller than Neptune (19/24 planets) as in the Kepler mission and all have short periods (P<50 d) due to the duration of the K2 photometry. The host stars are relatively bright (most have Kp<12.5 mag) and are amenable to follow-up planet characterization. For EPIC 204221263, we measured precise radial velocities using Keck/HIRES and provide initial estimates of the planet masses. EPIC 204221263b is a short-period super-Earth with a radius of 1.55±0.16R⊕, a mass of 12.0±2.9M⊕, and a high density consistent with an iron-rich composition. The outer planet EPIC 204221263c is a lower density sub-Neptune-size planet with a radius of 2.42±0.29R⊕ and a mass of 9.9±4.6M⊕ that likely has a substantial envelope. This new planet sample demonstrates the capability of K2 to discover numerous planetary systems around bright stars.
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The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion
[1511.09097] The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion
(Submitted on 29 Nov 2015)
Detection of an atmosphere around the super-Earth 55 Cancri e
A. Tsiaras, M. Rocchetto, I. P. Waldmann, O. Venot, R. Varley, G. Morello, G. Tinetti, E. J. Barton, S. N. Yurchenko, J. Tennyson
(Submitted on 28 Nov 2015)
[1511.08901] Detection of an atmosphere around the super-Earth 55 Cancri e
[1511.09213] Ten Multi-planet Systems from K2 Campaigns 1 & 2 and the Masses of Two Hot Super-Earths
http://arxiv.org/pdf/1511.09213v1.pdf
Evan Sinukoff, Andrew W. Howard, Erik A. Petigura, Joshua E. Schlieder, Ian J. M. Crossfield, David R. Ciardi, Benjamin J. Fulton, Howard Isaacson, Kimberly M. Aller, Christoph Baranec, Charles A. Beichman, Brad M. S. Hansen, Heather A. Knutson, Nicholas M. Law, Michael C. Liu, Reed Riddle
(Submitted on 30 Nov 2015)
We present a catalog of 10 multi-planet systems from Campaigns 1 and 2 of the K2 mission. We report the sizes and orbits of 24 planets split between six 2-planet systems and four 3-planet systems. These planets stem from a systematic search of the K2 photometry for all dwarf stars observed by K2 in these fields. We precisely characterized the host stars with adaptive optics imaging and analysis of high-resolution optical spectra from Keck/HIRES and medium-resolution spectra from IRTF/SpeX. The planets are mostly smaller than Neptune (19/24 planets) as in the Kepler mission and all have short periods (P<50 d) due to the duration of the K2 photometry. The host stars are relatively bright (most have Kp<12.5 mag) and are amenable to follow-up planet characterization. For EPIC 204221263, we measured precise radial velocities using Keck/HIRES and provide initial estimates of the planet masses. EPIC 204221263b is a short-period super-Earth with a radius of 1.55±0.16R⊕, a mass of 12.0±2.9M⊕, and a high density consistent with an iron-rich composition. The outer planet EPIC 204221263c is a lower density sub-Neptune-size planet with a radius of 2.42±0.29R⊕ and a mass of 9.9±4.6M⊕ that likely has a substantial envelope. This new planet sample demonstrates the capability of K2 to discover numerous planetary systems around bright stars.
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The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion
[1511.09097] The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion
(Submitted on 29 Nov 2015)
Kepler-454 (KOI-273) is a relatively bright (V = 11.69 mag), Sun-like starthat hosts a transiting planet candidate in a 10.6 d orbit. From spectroscopy, we estimate the stellar temperature to be 5687 +/- 50 K, its metallicity to be [m/H] = 0.32 +/- 0.08, and the projected rotational velocity to be v sin i <2.4 km s-1. We combine these values with a study of the asteroseismic frequencies from short cadence Kepler data to estimate the stellar mass to be 1.028+0:04-0:03 M_Sun, the radius to be 1.066 +/- 0.012 R_Sun and the age to be 5.25+1:41-1:39 Gyr. We estimate the radius of the 10.6 d planet as 2.37 +/- 0.13 R_Earth. Using 63 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 36 observations made with the HIRES spectrograph at Keck Observatory, we measure the mass of this planet to be 6.8 +/- 1.4M_Earth. We also detect two additional non-transiting companions, a planet with a minimum mass of 4.46 +/- 0.12 M_J in a nearly circular 524 d orbit and a massive companion with a period >10 years and mass >12.1M_J . The twelve exoplanets with radii <2.7 R_Earth and precise mass measurements appear to fall into two populations, with those <1.6 R_Earth following an Earth-like composition curve and larger planets requiring a significant fraction of volatiles. With a density of 2.76 +/- 0.73 g cm-3, Kepler-454b lies near the mass transition between these two populations and requires the presence of volatiles and/or H/He gas.
Detection of an atmosphere around the super-Earth 55 Cancri e
A. Tsiaras, M. Rocchetto, I. P. Waldmann, O. Venot, R. Varley, G. Morello, G. Tinetti, E. J. Barton, S. N. Yurchenko, J. Tennyson
(Submitted on 28 Nov 2015)
Before the discovery of extrasolar planets, super-Earths belonged in the realm of science fiction. However, they appear to constitute the most common planetary type in our galaxy. We know very little about these planets beyond very basic planetary and orbital parameters. The WFC3 camera onboard the HST has enabled the spectroscopic observations of the atmospheres of two super-Earths, GJ1214b and HD97658b, with unprecedented precision; but the published spectra of these two objects are featureless, suggesting an atmosphere covered by thick clouds or made of molecular species much heavier than hydrogen. We report here the analysis of the observations performed with the WFC3 of a third, very hot, super-Earth, 55 Cancri e. Given the brightness of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length and a very high scanning speed. These observational parameters are coupled with the geometrical distortions of the instrument, so we have developed a specialized pipeline to de-correlate the signal from the systematics. We measure the transit depth per wavelength channel with an average relative uncertainty of 21 ppm and find a spectral modulation of about 100 ppm. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is hydrogen-rich. Our fully Bayesian spectral retrieval code, TauREx, has identified HCN to be one of the possible trace gases in the atmosphere. While additional observations in a broader wavelength range will be needed to confirm the HCN detection, we discuss here the implications of such result. We adopt a chemical scheme developed with combustion specialists and validated by a wide range of experiments. Our chemical model indicates that a relatively high mixing ratio of HCN would reveal a high C/O ratio, suggesting the atmosphere of 55 Cancri e is a carbon-rich environment.
[1511.08901] Detection of an atmosphere around the super-Earth 55 Cancri e
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