1,312 research outputs found
Chromospheric CaII Emission in Nearby F, G, K, and M stars
We present chromospheric CaII activity measurements, rotation periods and
ages for ~1200 F-, G-, K-, and M- type main-sequence stars from ~18,000
archival spectra taken at Keck and Lick Observatories as a part of the
California and Carnegie Planet Search Project. We have calibrated our
chromospheric S values against the Mount Wilson chromospheric activity data.
From these measurements we have calculated median activity levels and derived
R'HK, stellar ages, and rotation periods for 1228 stars, ~1000 of which have no
previously published S values. We also present precise time series of activity
measurements for these stars.Comment: 62 pages, 7 figures, 1 table. Second (extremely long) table is
available at http://astro.berkeley.edu/~jtwright/CaIIdata/tab1.tex Accepted
by ApJ
The Lick-Carnegie Exoplanet Survey: A Saturn-Mass Planet in the Habitable Zone of the Nearby M4V Star HIP 57050
Precision radial velocities from Keck/HIRES reveal a Saturn-mass planet
orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of 0.3
Jupiter-mass, an orbital period of 41.4 days, and an orbital eccentricity of
0.31. V-band photometry reveals a clear stellar rotation signature of the host
star with a period of 98 days, well separated from the period of the radial
velocity variations and reinforcing a Keplerian origin for the observed
velocity variations. The orbital period of this planet corresponds to an orbit
in the habitable zone of HIP 57050, with an expected planetary temperature of
approximately 230 K. The star has a metallicity of [Fe/H] = 0.32+/-0.06 dex, of
order twice solar and among the highest metallicity stars in the immediate
solar neighborhood. This newly discovered planet provides further support that
the well-known planet-metallicity correlation for F, G, and K stars also
extends down into the M-dwarf regime. The a priori geometric probability for
transits of this planet is only about 1%. However, the expected eclipse depth
is ~7%, considerably larger than that yet observed for any transiting planet.
Though long on the odds, such a transit is worth pursuing as it would allow for
high quality studies of the atmosphere via transmission spectroscopy with HST.
At the expected planetary effective temperature, the atmosphere may contain
water clouds.Comment: 20 pages, 5 figures, 3 tables, to appear in the May 20 issue of ApJ
The Lick-Carnegie Survey: A New Two-Planet System Around the Star HD 207832
Keck/HIRES precision radial velocities of HD 207832 indicate the presence of
two Jovian-type planetary companions in Keplerian orbits around this G star.
The planets have minimum masses of 0.56 and 0.73 Jupiter-masses with orbital
periods of ~162 and ~1156 days, and eccentricities of 0.13 and 0.27,
respectively. Stromgren b and y photometry reveals a clear stellar rotation
signature of the host star with a period of 17.8 days, well separated from the
period of the radial velocity variations, reinforcing their Keplerian origin.
The values of the semimajor axes of the planets suggest that these objects have
migrated from the region of giant planet formation to closer orbits. In order
to examine the possibility of the existence of additional (small) planets in
the system, we studied the orbital stability of hypothetical terrestrial-sized
objects in the region between the two planets and interior to the orbit of the
inner body. Results indicated that stable orbits exist only in a small region
interior to planet b. However, the current observational data offer no evidence
for the existence of additional objects in this system.Comment: 23 pages, 4 figures, 5 tables, accepted for publication in Ap
Sub-Saturn Planet Candidates to HD 16141 and HD 46375
Precision Doppler measurements from the Keck/HIRES spectrometer reveal
periodic Keplerian velocity variations in the stars HD 16141 and HD 46375. HD
16141 (G5 IV) has a period of 75.8 d and a velocity amplitude of 11 m/s,
yielding a companion having Msini = 0.22 Mjup and a semimajor axis, a = 0.35
AU. HD 46375 (K1 IV/V) has a period of 3.024 d and a velocity amplitude of 35
m/s, yielding a companion with Msini=0.25 Mjup, a semimajor axis of a = 0.041
AU, and an eccentricity of 0.04 (consistent with zero). These companions
contribute to the rising planet mass function toward lower masses.Comment: 4 Figure
A Planetary Companion to the Nearby M4 Dwarf, Gliese 876
Doppler measurements of the M4 dwarf star, Gliese 876, taken at both Lick and
Keck Observatory reveal periodic, Keplerian velocity variations with a period
of 61 days. The orbital fit implies that the companion has a mass of, M = 2.1
MJUP /sin i, an orbital eccentricity of, e = 0.27+-0.03, and a semimajor axis
of, a = 0.21 AU. The planet is the first found around an M dwarf, and was drawn
from a survey of 24 such stars at Lick Observatory. It is the closest
extrasolar planet yet found, providing opportunities for follow--up detection.
The presence of a giant planet on a non-circular orbit, 0.2 AU from a 1/3 M_Sun
star, presents a challenge to planet formation theory. This planet detection
around an M dwarf suggests that giant planets are numerous in the Galaxy.Comment: 13 pages, 3 Figure
On the 2:1 Orbital Resonance in the HD 82943 Planetary System
We present an analysis of the HD 82943 planetary system based on a radial
velocity data set that combines new measurements obtained with the Keck
telescope and the CORALIE measurements published in graphical form. We examine
simultaneously the goodness of fit and the dynamical properties of the best-fit
double-Keplerian model as a function of the poorly constrained eccentricity and
argument of periapse of the outer planet's orbit. The fit with the minimum
chi_{nu}^2 is dynamically unstable if the orbits are assumed to be coplanar.
However, the minimum is relatively shallow, and there is a wide range of fits
outside the minimum with reasonable chi_{nu}^2. For an assumed coplanar
inclination i = 30 deg. (sin i = 0.5), only good fits with both of the lowest
order, eccentricity-type mean-motion resonance variables at the 2:1
commensurability, theta_1 and theta_2, librating about 0 deg. are stable. For
sin i = 1, there are also some good fits with only theta_1 (involving the inner
planet's periapse longitude) librating that are stable for at least 10^8 years.
The libration semiamplitudes are about 6 deg. for theta_1 and 10 deg. for
theta_2 for the stable good fit with the smallest libration amplitudes of both
theta_1 and theta_2. We do not find any good fits that are non-resonant and
stable. Thus the two planets in the HD 82943 system are almost certainly in 2:1
mean-motion resonance, with at least theta_1 librating, and the observations
may even be consistent with small-amplitude librations of both theta_1 and
theta_2.Comment: 24 pages, including 10 figures; accepted for publication in Ap
A 4-Planet System Orbiting the K0V Star HD 141399
We present precision radial velocity (RV) data sets from Keck-HIRES and from
Lick Observatory's new Automated Planet Finder Telescope and Levy Spectrometer
on Mt. Hamilton that reveal a multiple-planet system orbiting the nearby,
slightly evolved, K-type star HD 141399. Our 91 observations over 10.5 years
suggest the presence of four planets with orbital periods of 94.35, 202.08,
1070.35, and 3717.35 days and minimum masses of 0.46, 1.36, 1.22, and 0.69
Jupiter masses respectively. The orbital eccentricities of the three inner
planets are small, and the phase curves are well sampled. The inner two planets
lie just outside the 2:1 resonance, suggesting that the system may have
experienced dissipative evolution during the protoplanetary disk phase. The
fourth companion is a Jupiter-like planet with a Jupiter-like orbital period.
Its orbital eccentricity is consistent with zero, but more data will be
required for an accurate eccentricity determination.Comment: 11 pages, 13 figures, To appear in the Astrophysical Journa
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