The determination of exoplanet properties and occurrence rates using Kepler data critically depends on our knowledge of the fundamental properties (such as temperature, radius, and mass) of the ...observed stars. We present revised stellar properties for 197,096 Kepler targets observed between Quarters 1-17 (Q1-17), which were used for the final transiting planet search run by the Kepler Mission (Data Release 25, DR25). Similar to the Q1-16 catalog by Huber et al., the classifications are based on conditioning published atmospheric parameters on a grid of Dartmouth isochrones, with significant improvements in the adopted method and over 29,000 new sources for temperatures, surface gravities, or metallicities. In addition to fundamental stellar properties, the new catalog also includes distances and extinctions, and we provide posterior samples for each stellar parameter of each star. Typical uncertainties are ∼27% in radius, ∼17% in mass, and ∼51% in density, which is somewhat smaller than previous catalogs because of the larger number of improved constraints and the inclusion of isochrone weighting when deriving stellar posterior distributions. On average, the catalog includes a significantly larger number of evolved solar-type stars, with an increase of 43.5% in the number of subgiants. We discuss the overall changes of radii and masses of Kepler targets as a function of spectral type, with a particular focus on exoplanet host stars.
Abstract
We present the latest and most precise characterization of the architecture for the ancient (≈11 Gyr) Kepler-444 system, which is composed of a K0 primary star (Kepler-444 A) hosting five ...transiting planets and a tight M-type spectroscopic binary (Kepler-444 BC) with an A–BC projected separation of 66 au. We have measured the system’s relative astrometry using the adaptive optics imaging from Keck/NIRC2 and Kepler-444 A’s radial velocities from the Hobby-Eberly Telescope and reanalyzed relative radial velocities between BC and A from Keck/HIRES. We also include the Hipparcos-Gaia astrometric acceleration and all published astrometry and radial velocities in an updated orbit analysis of BC’s barycenter. These data greatly extend the time baseline of the monitoring and lead to significant updates to BC’s barycentric orbit compared to previous work, including a larger semimajor axis (
a
=
52.2
−
2.7
+
3.3
au), a smaller eccentricity (
e
= 0.55 ± 0.05), and a more precise inclination (
i
=
85
.°
4
−
0
.°
4
+
0
.°
3
). We have also derived the first dynamical masses of B and C components. Our results suggest that Kepler-444 A’s protoplanetary disk was likely truncated by BC to a radius of ≈8 au, which resolves the previously noticed tension between Kepler-444 A’s disk mass and planet masses. Kepler-444 BC’s barycentric orbit is likely aligned with those of A’s five planets, which might be primordial or a consequence of dynamical evolution. The Kepler-444 system demonstrates that compact multiplanet systems residing in hierarchical stellar triples can form at early epochs of the universe and survive their secular evolution throughout cosmic time.
Abstract
We present the discovery of a white dwarf companion to the G1 V star 12 Psc found as part of a Keck adaptive optics imaging survey of long-term accelerating stars from the McDonald ...Observatory Planet Search Program. Twenty years of precise radial-velocity monitoring of 12 Psc with the Tull Spectrograph at the Harlan J. Smith telescope reveals a moderate radial acceleration (≈10 m s
−1
yr
−1
), which together with relative astrometry from Keck/NIRC2 and the astrometric acceleration between Hipparcos and Gaia DR2 yields a dynamical mass of
M
B
=
M
⊙
for 12 Psc B, a semimajor axis of
au, and an eccentricity of 0.84 ± 0.08. We also report an updated orbital fit of the white dwarf companion to the metal-poor (but barium-rich) G9 V dwarf HD 159062 based on new radial-velocity observations from the High-Resolution Spectrograph at the Hobby–Eberly Telescope and astrometry from Keck/NIRC2. A joint fit of the available relative astrometry, radial velocities, and tangential astrometric acceleration yields a dynamical mass of
M
B
=
M
⊙
for HD 159062 B, a semimajor axis of
au, and preference for circular orbits (
e
< 0.42 at 95% confidence). 12 Psc B and HD 159062 B join a small list of resolved Sirius-like benchmark white dwarfs with precise dynamical mass measurements which serve as valuable tests of white dwarf mass–radius cooling models and probes of AGB wind accretion onto their main-sequence companions.
Abstract
Brown dwarfs with well-determined ages, luminosities, and masses provide rare but valuable tests of low-temperature atmospheric and evolutionary models. We present the discovery and ...dynamical mass measurement of a substellar companion to HD 47127, an old (≈7–10 Gyr) G5 main-sequence star with a mass similar to the Sun. Radial velocities of the host star with the Harlan J. Smith Telescope uncovered a low-amplitude acceleration of 1.93 ± 0.08 m s
−1
yr
−1
based on 20 years of monitoring. We subsequently recovered a faint (Δ
H
= 13.14 ± 0.15 mag) comoving companion at 1.″95 (52 au) with follow-up Keck/NIRC2 adaptive optics imaging. The radial acceleration of HD 47127 together with its tangential acceleration from Hipparcos and Gaia EDR3 astrometry provide a direct measurement of the three-dimensional acceleration vector of the host star, enabling a dynamical mass constraint for HD 47127 B (67.5–177
M
Jup
at 95% confidence) despite the small fractional orbital coverage of the observations. The absolute
H
-band magnitude of HD 47127 B is fainter than the benchmark T dwarfs HD 19467 B and Gl 229 B but brighter than Gl 758 B and HD 4113 C, suggesting a late-T spectral type. Altogether the mass limits for HD 47127 B from its dynamical mass and the substellar boundary imply a range of 67–78
M
Jup
assuming it is single, although a preference for high masses of ≈100
M
Jup
from dynamical constraints hints at the possibility that HD 47127 B could itself be a binary pair of brown dwarfs or that another massive companion resides closer in. Regardless, HD 47127 B will be an excellent target for more refined orbital and atmospheric characterization in the future.
Abstract
Gl 758 B is a late-T dwarf orbiting a metal-rich Sun-like star at a projected separation of
ρ
≈ 1.″6 (25 au). We present four epochs of astrometry of this system with NIRC2 at Keck ...Observatory spanning 2010 to 2017 together with 630 radial velocities (RVs) of the host star acquired over the past two decades from McDonald Observatory, Keck Observatory, and the Automated Planet Finder at Lick Observatory. The RVs reveal that Gl 758 is accelerating with an evolving rate that varies between 2 and 5 m s
−1
yr
−1
, consistent with the expected influence of the imaged companion Gl 758 B. A joint fit of the RVs and astrometry yields a dynamical mass of
M
Jup
for the companion with a robust lower limit of 30.5
M
Jup
at the 4-
σ
level. Gl 758 B is on an eccentric orbit (
e
= 0.26–0.67 at 95% confidence) with a semimajor axis of
a
=
au and an orbital period of
P
=
yr, which takes it within ≈9 au from its host star at periastron passage. Substellar evolutionary models generally underpredict the mass of Gl 758 B for nominal ages of 1–6 Gyr that have previously been adopted for the host star. This discrepancy can be reconciled if the system is older—which is consistent with activity indicators and recent isochrone fitting of the host star—or alternatively if the models are systematically overluminous by ≈0.1–0.2 dex. Gl 758 B is currently the lowest-mass directly imaged companion inducing a measured acceleration on its host star. In the future, bridging RVs and high-contrast imaging with the next generation of extremely large telescopes and space-based facilities will open the door to the first dynamical mass measurements of imaged exoplanets.
Kepler-91b is a rare example of a transiting hot Jupiter around a red giant star, providing the possibility to study the formation and composition of hot Jupiters under different conditions compared ...to main-sequence stars. However, the planetary nature of Kepler-91b, which was confirmed using phase-curve variations by Lillo-Box et al., was recently called into question based on a re-analysis of Kepler data. We have obtained ground-based radial velocity observations from the Hobby-Eberly Telescope and unambiguously confirm the planetary nature of Kepler-91b by simultaneously modeling the Kepler and radial velocity data. The star exhibits temporally correlated noise due to stellar granulation which we model as a Gaussian Process. We hypothesize that it is this noise component that led previous studies to suspect Kepler-91b to be a false positive. Our work confirms the conclusions presented by Lillo-Box et al. that Kepler-91b is a 0.73 + or - 0.13 M sub(Jup) planet orbiting a red giant star.
ABSTRACT The nearby (6.5 pc) star HD 219134 was recently shown by Motalebi et al. and Vogt et al. to host several planets, the innermost of which is transiting. We present 27 years of radial velocity ...(RV) observations of this star from the McDonald Observatory Planet Search program, and 19 years of stellar activity data. We detect a long-period activity cycle measured in the Ca ii SHK index, with a period of 4230 100 days (11.7 years), very similar to the 11 year solar activity cycle. Although the period of the Saturn-mass planet HD 219134 h is close to half that of the activity cycle, we argue that it is not an artifact due to stellar activity. We also find a significant periodicity in the SHK data due to stellar rotation with a period of 22.8 days. This is identical to the period of planet f identified by Vogt et al., suggesting that this RV signal might be caused by rotational modulation of stellar activity rather than a planet. Analysis of our RVs allows us to detect the long-period planet HD 219134 h and the transiting super-Earth HD 219134 b. Finally, we use our long time baseline to constrain the presence of longer period planets in the system, excluding to 1 objects with M sin i > 0.36 M J at 12 years (corresponding to the orbital period of Jupiter) and M sin i > 0.72 M J at a period of 16.4 years (assuming a circular orbit for an outer companion).
We discuss our high-precision radial velocity results of a sample of 90 M dwarfs observed with the Hobby-Eberly Telescope and the Harlan J. Smith 2.7 m Telescope at McDonald Observatory, as well as ...the ESO VLT and the Keck I telescopes, within the context of the overall frequency of Jupiter-mass planetary companions to main-sequence stars. None of the stars in our sample show variability indicative of a giant planet in a short-period orbit, with a ,1 AU. We estimate an upper limit of the frequencyf of close-in Jovian planets around M dwarfs as <1.27% (at the 1 sconfidence level). Furthermore, we determine that the efficiency of our survey in noticing planets in circular orbits is 98% for companions with m sin i > 3.8M sub(J) and a ,0.7 AU. For eccentric orbits (e = 0.6) the survey completeness is 95% for all planets with m sin i > 3.5M sub(J) and a ,0.7 AU. Our results point toward a generally lower frequency of close-in Jovian planets for M dwarfs as compared to FGK-type stars. This is an important piece of information for our understanding of the process of planet formation as a function of stellar mass.
We present a catalog of emission-line galaxies selected solely by their emission-line fluxes using a wide-field integral field spectrograph. This work is partially motivated as a pilot survey for the ...upcoming Hobby-Eberly Telescope Dark Energy Experiment. We describe the observations, reductions, detections, redshift classifications, line fluxes, and counterpart information for 397 emission-line galaxies detected over 169 ' with a 3500-5800 A bandpass under 5 A full-width-half-maximum (FWHM) spectral resolution. The survey's best sensitivity for unresolved objects under photometric conditions is between 4 and 20X 10--17 erg s--1 cm--2 depending on the wavelength, and Ly Delta *a luminosities between 3 X 1042 and 6 X 1042 erg s--1 are detectable. This survey method complements narrowband and color-selection techniques in the search of high-redshift galaxies with its different selection properties and large volume probed. The four survey fields within the COSMOS, GOODS-N, MUNICS, and XMM-LSS areas are rich with existing, complementary data. We find 105 galaxies via their high-redshift Ly Delta *a emission at 1.9 < z < 3.8, and the majority of the remainder objects are low-redshift O II3727 emitters at z < 0.56. The classification between low- and high-redshift objects depends on rest-frame equivalent width (EW), as well as other indicators, where available. Based on matches to X-ray catalogs, the active galactic nuclei fraction among the Ly Delta *a emitters is 6%. We also analyze the survey's completeness and contamination properties through simulations. We find five high-z, highly significant, resolved objects with FWHM sizes >44 ' which appear to be extended Ly Delta *a nebulae. We also find three high-z objects with rest-frame Ly Delta *a EW above the level believed to be achievable with normal star formation, EW0>240 A. Future papers will investigate the physical properties of this sample.
Abstract
We report the detection of a long-period giant planetary companion to the nearby M3V star GJ 463 (=Ross 690). The detection is based on over ten years of highly-precise radial velocity ...measurements with the High Resolution Spectrograph at the Hobby–Eberly Telescope and the HIRES spectrograph at Keck. With an orbital period of 10 yr and a minimum mass of 1.55 ± 0.15
M
Jup
, GJ 463 b has a comparable orbital period to Jupiter and hence qualifies as a Jupiter analog around a low-mass star. We demonstrate that the radial velocity signal is not produced by a magnetic activity cycle of the host star. GJ 463 was observed with TESS, and we searched the light curve for any possible signals of stellar or planetary origin, but detected none. This planet is a candidate for possible direct detection with the coronagraph of the upcoming Nancy Grace Roman Space Telescope. We compared Gaia EDR3 with Hipparcos astrometry and detected a significant acceleration, which is likely caused by this long-period planetary companion at
a
= 3.53 ± 0.07 au.
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