| 1. |
- Nowak, G., et al.
(författare)
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EPIC 219388192b-An Inhabitant of the Brown Dwarf Desert in the Ruprecht 147 Open Cluster
- 2017
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 153:3
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Tidskriftsartikel (refereegranskat)abstract
- 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 R-b= 0.937 +/- 0.032 R-Jup and mass of M-b= 36.84 +/- 0.97 M-Jup, yielding a mean density of 59.6 +/- 7.6 g cm(- 3). The host star is nearly a solar twin with mass M-star = 1.01 +/- 0.04 Me, radius R-star = 1.01 +/- 0.03 R-circle dot, effective temperature T-eff = 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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| 2. |
- Livingston, J.H., et al.
(författare)
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44 Validated Planets from K2 Campaign 10
- 2018
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 156:2
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Tidskriftsartikel (refereegranskat)abstract
- 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 Rp = 2.2 R_earth , P_orb = 6.9 days, T_eq = 890 K, and J = 11.2 mag. Of particular interest are four ultra-short period planets (P_orb}≲ 1 day), 16 planets smaller than 2 R_earth, 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 (R_p ≈ 1–2 R_earth), sub-Neptunes (Rp ≈ 2–4 R_earth, and sub-Saturns (Rp ≈ 4–8 R_earth) orbiting bright stars (J = 8–10 mag) by ∼4%, ∼17%, and ∼11%, respectively.
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| 3. |
- Dai, F., et al.
(författare)
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The Discovery and Mass Measurement of a New Ultra-short-period Planet: K2-131
- 2017
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 154:6, s. 226-
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Tidskriftsartikel (refereegranskat)abstract
- 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, EPIC 228732031b, was discovered in K2 Campaign 10. It has a radius of 1.81-0.12+0.16 R_Earth 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 6.5+/- 1.6 M_Earth and a mean density of 6.0-2.7+3.0 g cm‑3.
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| 4. |
- Eigmüller, Philipp, et al.
(författare)
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AN M DWARF COMPANION TO AN F-TYPE STAR IN A YOUNG MAIN-SEQUENCE BINARY
- 2016
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 151:3
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Tidskriftsartikel (refereegranskat)abstract
- Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung-Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectroscopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493 +/- 0.073) M-circle dot and a radius of (1.474 +/- 0.040) R-circle dot. The companion is an M dwarf with a mass of (0.188 +/- 0.014) M-circle dot and a radius of (0.234 +/- 0.009) R-circle dot. The orbital period is (1.35121 +/- 0.00001) days. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1: 1 spin-orbit synchronization. This indicates a young main-sequence binary with an age below similar to 250 Myr. The mass-radius relation of both components are in agreement with this finding.
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| 5. |
- Grziwa, S., et al.
(författare)
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K2-31B, a Grazing Transiting Hot Jupiter on a 1.26-Day Orbit Around a Bright G7v Star
- 2016
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 152:5
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of K2-31b, the first confirmed transiting hot Jupiter detected by the K2 space mission. We combined K2 photometry with FastCam lucky imaging and FIES and HARPS high-resolution spectroscopy to confirm the planetary nature of the transiting object and derived the system parameters. K2-31b is a 1.8-Jupiter-mass planet on a. 1.26-day orbit around a G7 V star (M-star = 0.91 M-circle dot, R-star = 0.78 R-circle dot). The planetary radius is poorly constrained (0.7
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| 6. |
- Johnson, M. C., et al.
(författare)
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TWO HOT JUPITERS FROM K2 CAMPAIGN 4
- 2016
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 151:6
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Tidskriftsartikel (refereegranskat)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 coude 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) R-J and a mass of M-p = 0.6131-0.613-0.026 M-J. Its host star exhibits significant rotational variability, and we measure a rotation period of pot = 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) Ri 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, [Fe/H] = 0.15 +/- 0.05.
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| 7. |
- Mottola, S, et al.
(författare)
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Physical model of near-Earth asteroid 6489 Golevka (1991 JX) from optical and infrared observations
- 1997
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Ingår i: ASTRONOMICAL JOURNAL. - : AMER INST PHYSICS. - 0004-6256. ; 114:3, s. 1234-1245
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In 1995 asteroid 6489 Golevka (1991 JX) had a close encounter with the Earth at a distance of 0.034 AU, providing a good opportunity for a detailed study of a small Solar System object. In this paper we report the results of an extensive international obs
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