We describe a 20 year survey carried out by the Lick-Carnegie Exoplanet Survey Team (LCES), using precision radial velocities from HIRES on the Keck I telescope to find and characterize extrasolar ...planetary systems orbiting nearby F, G, K, and M dwarf stars. We provide here 60,949 precision radial velocities for 1624 stars contained in that survey. We tabulate a list of 357 significant periodic signals that are of constant period and phase, and not coincident in period and/or phase with stellar activity indices. These signals are thus strongly suggestive of barycentric reflex motion of the star induced by one or more candidate exoplanets in Keplerian motion about the host star. Of these signals, 225 have already been published as planet claims, 60 are classified as significant unpublished planet candidates that await photometric follow-up to rule out activity-related causes, and 54 are also unpublished, but are classified as "significant" signals that require confirmation by additional data before rising to classification as planet candidates. Of particular interest is our detection of a candidate planet with , and P = 9.9 days orbiting Lalande 21185, the fourth-closest main-sequence star to the Sun. For each of our exoplanetary candidate signals, we provide the period and semi-amplitude of the Keplerian orbital fit, and a likelihood ratio estimate of its statistical significance. We also tabulate 18 Keplerian-like signals that we classify as likely arising from stellar activity.
We analyze 8 years of precise radial velocity measurements from the Keck Planet Search, characterizing the detection threshold, selection effects, and completeness of the survey. We first carry out a ...systematic search for planets, by assessing the false-alarm probability associated with Keplerian orbit fits to the data. This allows us to understand the detection threshold for each star in terms of the number and time baseline of the observations, and the underlying “noise” from measurement errors, intrinsic stellar jitter, or additional low-mass planets. We show that all planets with orbital periods
P < 2000 days
P
<
2000
days
, velocity amplitudes
K > 20 m s-1
K
>
20
m
s
-
1
, and eccentricities
e ≲ 0.6
e
≲
0.6
have been announced, and we summarize the candidates at lower amplitudes and longer orbital periods. For the remaining stars, we calculate upper limits on the velocity amplitude of a companion. For orbital periods less than the duration of the observations, these are typically10 m s-1
10
m
s
-
1
and increase∝ P
2
∝
P
2
for longer periods. We then use the nondetections to derive completeness corrections at low amplitudes and long orbital periods and discuss the resulting distribution of minimum mass and orbital period. We give the fraction of stars with a planet as a function of minimum mass and orbital period and extrapolate to long-period orbits and low planet masses. A power-law fit for planet masses>0.3 M
J
>
0.3
M
J
and periods< 2000 days
<
2000
days
gives a mass-period distribution
dN = CM
α
P
β
d ln Md ln P
d
N
=
C
M
α
P
β
d
ln
M
d
ln
P
withα = -0.31 ± 0.2
α
=
-
0.31
±
0.2
,β = 0.26 ± 0.1
β
=
0.26
±
0.1
, and the normalization constant
C
C
such that 10.5% of solar type stars have a planet with mass in the range0.3–10 M
J
0.3
–
10
M
J
and orbital period 2–2000 days. The orbital period distribution shows an increase in the planet fraction by a factor of≈5
≈
5
for orbital periods≳300 days
≳
300
days
. Extrapolation gives 17%–20% of stars having gas giant planets within 20 AU. Finally, we constrain the occurrence rate of planets orbiting M dwarfs compared to FGK dwarfs, taking into account differences in detectability.
Revised orbits of the two nearest Jupiters Feng, Fabo; Butler, R Paul; Vogt, Steven S ...
Monthly Notices of the Royal Astronomical Society,
08/2023, Volume:
525, Issue:
1
Journal Article
Peer reviewed
Open access
ABSTRACT
With its near-to-mid-infrared high-contrast imaging capabilities, JWST is ushering us into a golden age of directly imaging Jupiter-like planets. As the two closest cold Jupiters, ε Ind A b ...and ε Eridani b have sufficiently wide orbits and adequate infrared emissions to be detected by JWST. To detect more Jupiter-like planets for direct imaging, we develop a gost-based method to analyse radial velocity data and multiple Gaia data releases simultaneously. Without approximating instantaneous astrometry by catalogue astrometry, this approach enables the use of multiple Gaia data releases for detection of both short-period and long-period planets. We determine a mass of $2.96_{-0.38}^{+0.41}$ MJup and a period of $42.92_{-4.09}^{+6.38}$ yr for ε Ind A b. We also find a mass of $0.76_{-0.11}^{+0.14}$ MJup , a period of $7.36_{-0.05}^{+0.04}$ yr, and an eccentricity of 0.26$_{-0.04}^{+0.04}$ MJup, for ε Eridani b. The eccentricity differs from that given by some previous solutions, probably due to the sensitivity of orbital eccentricity to noise modelling. Our work refines the constraints on orbits and masses of the two nearest Jupiters and demonstrate the feasibility of using multiple Gaia data releases to constrain Jupiter-like planets.
We report precise Doppler measurements of GJ 317 (M3.5 V) that reveal the presence of a planet with a minimum mass Mpsin i = 1.2 M sub(Jup) eccentric, 692.9 day orbit. GJ 317 is only the third M ...dwarf with a Doppler-detected Jovian planet. The residuals to a single-Keplerian fit show evidence of a possible second orbital companion. The inclusion of a second Jupiter-mass planet (P approximately 2700 days, Mpsin i = 0.83 M sub(Jup)) decreases unk from 2.02 to 1.23, and reduces the rms from 12.5 to 6.32 m s super(-1). A false-alarm test yields a 1.1% probability that the curvature in the residuals of the single-planet fit is due to random fluctuations, lending additional credibility to the two-planet model. However, our data only marginally constrain a two-planet fit, and further monitoring is necessary to fully characterize the properties of the second companion. To study the effect of stellar mass on giant planet occurrence, we measure the fraction of stars with planets in three mass bins comprised of our samples of M Dwarfs, solar-mass stars, and intermediate-mass subgiants. We find a positive correlation between stellar mass and the occurrence rate of Jovian planets within 2.5 AU. Low-mass K and M stars have a 1.8% plus or minus 1.0% planet occurrence rate compared to 4.2% plus or minus 0.7% for solar-mass stars and 8.9 plus or minus 2.9% for the higher mass subgiants. This result indicates that the former F- and A-type stars with M unk greater than or equal to 1.3 M unk in our sample are nearly 5 times more likely than the M dwarfs to harbor a giant planet. Our analysis shows that the correlation between Jovian planet occurrence and stellar mass exists even after correcting for the effects of stellar metallicity.
SIX PLANETS ORBITING HD 219134 Vogt, Steven S.; Burt, Jennifer; Meschiari, Stefano ...
The Astrophysical journal,
11/2015, Volume:
814, Issue:
1
Journal Article
Peer reviewed
ABSTRACT We present new, high-precision Doppler radial velocity (RV) data sets for the nearby K3V star HD 219134. The data include 175 velocities obtained with the HIRES Spectrograph at the Keck I ...Telescope and 101 velocities obtained with the Levy Spectrograph at the Automated Planet Finder Telescope at Lick Observatory. Our observations reveal six new planetary candidates, with orbital periods of P = 3.1, 6.8, 22.8, 46.7, 94.2, and 2247 days, spanning masses of 3.5, 8.9, 21.3, 10.8, and , respectively. Our analysis indicates that the outermost signal is unlikely to be an artifact induced by stellar activity. In addition, several years of precision photometry with the T10 0.8 m automatic photometric telescope at Fairborn Observatory demonstrated a lack of brightness variability to a limit of ∼0.0002 mag, providing strong support for planetary-reflex motion as the source of the RV variations. The HD 219134 system with its bright (V = 5.6) primary provides an excellent opportunity to obtain detailed orbital characterization (and potentially follow-up observations) of a planetary system that resembles many of the multiple-planet systems detected by Kepler, which are expected to be detected by NASA's forthcoming TESS Mission and by ESA's forthcoming PLATO Mission.
We use 3D simulations to study the atmospheric circulation on the first Earth-sized exoplanet discovered in the habitable zone of an M star. We treat Gliese 581g as a scaled-up version of Earth by ...considering increased values for the exoplanetary radius and surface gravity, while retaining terrestrial values for parameters which are unconstrained by current observations. We examine the long-term, global temperature and wind maps near the surface of the exoplanet - the climate. The specific locations for habitability on Gliese 581g depend on whether the exoplanet is tidally locked and how fast radiative cooling occurs on a global scale. Independent of whether the existence of Gliese 581g is confirmed, our study highlights the use of general circulation models to quantify the atmospheric circulation on potentially habitable, Earth-sized exoplanets, which will be the prime targets of exoplanet discovery and characterization campaigns in the next decade.
We report the discovery of a radial velocity signal that can be interpreted as a planetary-mass candidate orbiting the K dwarf HD 26965, with an orbital period of 42.364 ± 0.015 days, or ...alternatively, as the presence of residual, uncorrected rotational activity in the data. Observations include data from HIRES, PFS, CHIRON, and HARPS, where 1111 measurements were made over 16 years. Our best solution for HD 26965 b is consistent with a super-Earth that has a minimum mass of 6.92 ± 0.79 \({M}_{\oplus }\) orbiting at a distance of 0.215 ± 0.008 au from its host star. We have analyzed the correlation between spectral activity indicators and the radial velocities from each instrument, showing moderate correlations that we include in our model. From this analysis, we recover a ∼38-day signal, which matches some literature values of the stellar rotation period. However, from independent Mt. Wilson HK data for this star, we find evidence for a significant 42-day signal after subtraction of longer period magnetic cycles, casting doubt on the planetary hypothesis for this period. Although our statistical model strongly suggests that the 42-day signal is Doppler in origin, we conclude that the residual effects of stellar rotation are difficult to fully model and remove from this data set, highlighting the difficulties to disentangle small planetary signals and photospheric noise, particularly when the orbital periods are close to the rotation period of the star. This study serves as an excellent test case for future works that aim to detect small planets orbiting “Sun-like” stars using radial velocity measurements.
Abstract
Measuring the obliquity distribution of stars hosting warm Jupiters may help us to understand the formation of close-orbiting gas giants. Few such measurements have been performed due to ...practical difficulties in scheduling observations of the relatively infrequent and long-duration transits of warm Jupiters. Here, we report a measurement of the Rossiter–McLaughlin effect for K2-232 b, a warm Jupiter on an 11.17 day orbit with an eccentricity of 0.26. The data were obtained with the Automated Planet Finder during two separate transits. The planet’s orbit appears to be well aligned with the spin axis of the host star, with a projected spin–orbit angle of
λ
= −11.°1 ± 6.°6. Combined with the other available data, we find that high obliquities are almost exclusively associated with planets that either have an orbital separation greater than 10 stellar radii or orbit stars with effective temperatures hotter than 6000 K. This pattern suggests that the obliquities of the closest-orbiting giant planets around cooler stars have been damped by tidal effects.
Context. Since low-mass stars have low luminosities, orbits at which liquid water can exist on Earth-sized planets are relatively close-in, which produces Doppler signals that are detectable using ...state-of-the-art Doppler spectroscopy. Aims. GJ 667C is already known to be orbited by two super-Earth candidates. We have recently applied developed data analysis methods to investigate whether the data supports the presence of additional companions. Methods. We obtain new Doppler measurements from HARPS extracted spectra and combined them with those obtained from the PFS and HIRES spectrographs. We used Bayesian and periodogram-based methods to re-assess the number of candidates and evaluated the confidence of each detection. Among other tests, we validated the planet candidates by analyzing correlations of each Doppler signal with measurements of several activity indices and investigated the possible quasi-periodic nature of signals. Results. Doppler measurements of GJ 667C are described better by six (even seven) Keplerian-like signals: the two known candidates (b and c); three additional few-Earth mass candidates with periods of 92, 62, and 39 days (d, e and f); a cold super-Earth in a 260-day orbit (g) and tantalizing evidence of a ~1 M⊕ object in a close-in orbit of 17 days (h). We explore whether long-term stable orbits are compatible with the data by integrating 8 × 104 solutions derived from the Bayesian samplings. We assess their stability using secular frequency analysis. Conclusions. The system consisting of six planets is compatible with dynamically stable configurations. As for the solar system, the most stable solutions do not contain mean-motion resonances and are described well by analytic Laplace-Lagrange solutions. Preliminary analysis also indicates that masses of the planets cannot be higher than twice the minimum masses obtained from Doppler measurements. The presence of a seventh planet (h) is supported by the fact that it appears squarely centered on the only island of stability left in the six-planet solution. Habitability assessments accounting for the stellar flux, as well as tidal dissipation effects, indicate that three (maybe four) planets are potentially habitable. Doppler and space-based transit surveys indicate that 1) dynamically packed systems of super-Earths are relatively abundant and 2) M-dwarfs have more small planets than earlier-type stars. These two trends together suggest that GJ 667C is one of the first members of an emerging population of M-stars with multiple low-mass planets in their habitable zones.
We present evidence for a new two-planet system around the giant star HD 202696 (=HIP 105056, BD +26 4118). The discovery is based on public HIRES radial velocity (RV) measurements taken at Keck ...Observatory between 2007 July and 2014 September. We estimate a stellar mass of for HD 202696, which is located close to the base of the red giant branch. A two-planet self-consistent dynamical modeling MCMC scheme of the RV data followed by a long-term stability test suggests planetary orbital periods of Pb = and Pc = days, eccentricities of eb = and ec = , and minimum dynamical masses of mb = and mc = MJup, respectively. Our stable MCMC samples are consistent with orbital configurations predominantly in a mean period ratio of 11:6 and its close-by high-order mean-motion commensurabilities with low eccentricities. For the majority of the stable configurations, we find an aligned or anti-aligned apsidal libration (i.e., Δ librating around 0° or 180°), suggesting that the HD 202696 system is likely dominated by secular perturbations near the high-order 11:6 mean-motion resonance. The HD 202696 system is yet another Jovian-mass pair around an intermediate-mass star with a period ratio below the 2:1 mean-motion resonance. Therefore, the HD 202696 system is an important discovery that may shed light on the primordial disk-planet properties needed for giant planets to break the strong 2:1 mean-motion resonance and settle in more compact orbits.
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