2,782 research outputs found
Revised Orbit and Transit Exclusion for HD 114762b
Transiting planets around bright stars have allowed the detailed follow-up
and characterization of exoplanets, such as the study of exoplanetary
atmospheres. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) is
refining the orbits of the known exoplanets to confirm or rule out both transit
signatures and the presence of additional companions. Here we present results
for the companion orbiting HD 114762 in an eccentric 84 day orbit. Radial
velocity analysis performed on 19 years of Lick Observatory data constrain the
uncertainty in the predicted time of mid-transit to ~5 hours, which is less
than the predicted one-half day transit duration. We find no evidence of
additional companions in this system. New photometric observations with one of
our Automated Photoelectric Telescopes (APTs) at Fairborn Observatory taken
during a revised transit time for companion b, along with 23 years of nightly
automated observations, allow us to rule out on-time central transits to a
limit of ~0.001 mag. Early or late central transits are ruled out to a limit of
~0.002 mag, and transits with half the duration of a central transit are ruled
out to a limit of ~0.003 mag.Comment: 5 pages, 2 figures, accepted for publication in ApJ
Retired A Stars and Their Companions IV. Seven Jovian Exoplanets from Keck Observatory
We report precise Doppler measurements of seven subgiants from Keck
Observatory. All seven stars show variability in their radial velocities
consistent with planet-mass companions in Keplerian orbits. The host stars have
masses ranging from 1.1 < Mstar/Msun < 1.9, radii 3.4 < Rstar/Rsun < 6.1, and
metallicities -0.21 < [Fe/H] < +0.26. The planets are all more massive than
Jupiter (Msini > 1 Mjup) and have semimajor axes > 1 AU. We present
millimagnitude photometry from the T3 0.4m APT at Fairborn observatory for five
of the targets. Our monitoring shows these stars to be photometrically stable,
further strengthening the interpretation of the observed radial velocity
variability. The orbital characteristics of the planets thus far discovered
around former A-type stars are very different from the properties of planets
around dwarf stars of spectral type F, G and K, and suggests that the formation
and migration of planets is a sensitive function of stellar mass. Three of the
planetary systems show evidence of long-term, linear trends indicative of
additional distant companions. These trends, together with the high planet
masses and increased occurrence rate, indicate that A-type stars are very
promising targets for direct imaging surveys.Comment: PASP Accepted, final submission awaiting comments from the communit
The California Planet Survey II. A Saturn-Mass Planet Orbiting the M Dwarf Gl649
We report precise Doppler measurements of the nearby (d = 10.34 pc) M dwarf
Gl649 that reveal the presence of a planet with a minimum mass Msini = 0.328
Mjup in an eccentric (e = 0.30), 598.3 day orbit. Our photometric monitoring
reveals Gl649 to be a new variable star with brightness changes on both
rotational and decadal timescales. However, neither of these timescales are
consistent with the 600-day Doppler signal and so provide strong support for
planetary reflex motion as the best interpretation of the observed radial
velocity variations. Gl649b is only the seventh Doppler-detected giant planet
around an M dwarf. The properties of the planet and host-star therefore
contribute significant information to our knowledge of planet formation around
low-mass stars. We revise and refine the occurrence rate of giant planets
around M dwarfs based on the California Planet Survey sample of low-mass stars
(M* < 0.6 Msun). We find that f = 3.4^{+2.2}_{-0.9}% of stars with M* < 0.6
Msun harbor planets with Msini > 0.3$ Mjup and a < 2.5 AU. When we restrict our
analysis to metal-rich stars with [Fe/H] > +0.2 we find the occurrence rate is
10.7^{+5.9}_{-4.2}%.Comment: 8 pages, 4 figures, 3 tables, PASP accepte
A High Eccentricity Component in the Double Planet System Around HD 163607 and a Planet Around HD 164509
We report the detection of three new exoplanets from Keck Observatory. HD
163607 is a metal-rich G5IV star with two planets. The inner planet has an
observed orbital period of 75.29 0.02 days, a semi-amplitude of 51.1
1.4 \ms, an eccentricity of 0.73 0.02 and a derived minimum mass of
\msini = 0.77 0.02 \mjup. This is the largest eccentricity of any known
planet in a multi-planet system. The argument of periastron passage is 78.7
2.0; consequently, the planet's closest approach to its parent
star is very near the line of sight, leading to a relatively high transit
probability of 8%. The outer planet has an orbital period of 3.60 0.02
years, an orbital eccentricity of 0.12 0.06 and a semi-amplitude of 40.4
1.3 \ms. The minimum mass is \msini = 2.29 0.16 \mjup. HD 164509 is
a metal-rich G5V star with a planet in an orbital period of 282.4 3.8
days and an eccentricity of 0.26 0.14. The semi-amplitude of 14.2
2.7 \ms\ implies a minimum mass of 0.48 0.09 \mjup. The radial velocities
of HD 164509 also exhibit a residual linear trend of -5.1 0.7 \ms\ per
year, indicating the presence of an additional longer period companion in the
system. Photometric observations demonstrate that HD 163607 and HD 164509 are
constant in brightness to sub-millimag levels on their radial velocity periods.
This provides strong support for planetary reflex motion as the cause of the
radial velocity variations.Comment: 10 pages, 8 figures, accepted to Ap
Survey of J=0,1 mesons in a Bethe-Salpeter approach
The Bethe-Salpeter equation is used to comprehensively study mesons with
J=0,1 and equal-mass constituents for quark masses from the chiral limit to the
b-quark mass. The survey contains masses of the ground states in all
corresponding J^{PC} channels including those with "exotic" quantum numbers.
The emphasis is put on each particular state's sensitivity to the low- and
intermediate-momentum, i.e., long-range part of the strong interaction.Comment: 8 pages, 4 figure
Two Exoplanets Discovered at Keck Observatory
We present two exoplanets detected at Keck Observatory. HD 179079 is a G5
subgiant that hosts a hot Neptune planet with Msini = 27.5 M_earth in a 14.48
d, low-eccentricity orbit. The stellar reflex velocity induced by this planet
has a semiamplitude of K = 6.6 m/s. HD 73534 is a G5 subgiant with a
Jupiter-like planet of Msini = 1.1 M_jup and K = 16 m/s in a nearly circular
4.85 yr orbit. Both stars are chromospherically inactive and metal-rich. We
discuss a known, classical bias in measuring eccentricities for orbits with
velocity semiamplitudes, K, comparable to the radial velocity uncertainties.
For exoplanets with periods longer than 10 days, the observed exoplanet
eccentricity distribution is nearly flat for large amplitude systems (K > 80
m/s), but rises linearly toward low eccentricity for lower amplitude systems (K
> 20 m/s).Comment: 8 figures, 6 tables, accepted, Ap
Five Intermediate-Period Planets from the N2K Sample
We report the detection of five Jovian mass planets orbiting high metallicity
stars. Four of these stars were first observed as part of the N2K program and
exhibited low RMS velocity scatter after three consecutive observations.
However, follow-up observations over the last three years now reveal the
presence of longer period planets with orbital periods ranging from 21 days to
a few years. HD 11506 is a G0V star with a planet of \msini = 4.74 \mjup in a
3.85 year orbit. HD 17156 is a G0V star with a 3.12 \mjup planet in a 21.2 day
orbit. The eccentricity of this orbit is 0.67, one of the highest known for a
planet with a relatively short period. The orbital period for this planet
places it in a region of parameter space where relatively few planets have been
detected. HD 125612 is a G3V star with a planet of \msini = 3.5 \mjup in a 1.4
year orbit. HD 170469 is a G5IV star with a planet of \msini = 0.67 \mjup in a
3.13 year orbit. HD 231701 is an F8V star with planet of 1.08 \mjup in a 142
day orbit. All of these stars have supersolar metallicity. Three of the five
stars were observed photometrically but showed no evidence of brightness
variability. A transit search conducted for HD 17156 was negative but covered
only 25% of the search space and so is not conclusive.Comment: 13 pages, 9 figures, accepted ApJ Resubmitted here with some
additional data, modified Keplerian orbit
The NASA-UC-UH Eta-Earth Program: IV. A Low-mass Planet Orbiting an M Dwarf 3.6 PC from Earth
We report the discovery of a low-mass planet orbiting Gl 15 A based on radial
velocities from the Eta-Earth Survey using HIRES at Keck Observatory. Gl 15 Ab
is a planet with minimum mass Msini = 5.35 0.75 M, orbital
period P = 11.4433 0.0016 days, and an orbit that is consistent with
circular. We characterize the host star using a variety of techniques.
Photometric observations at Fairborn Observatory show no evidence for
rotational modulation of spots at the orbital period to a limit of ~0.1 mmag,
thus supporting the existence of the planet. We detect a second RV signal with
a period of 44 days that we attribute to rotational modulation of stellar
surface features, as confirmed by optical photometry and the Ca II H & K
activity indicator. Using infrared spectroscopy from Palomar-TripleSpec, we
measure an M2 V spectral type and a sub-solar metallicity ([M/H] = -0.22,
[Fe/H] = -0.32). We measure a stellar radius of 0.3863 0.0021 R
based on interferometry from CHARA.Comment: ApJ accepted, 11 pages, 8 figures, 3 table
An Eccentric Hot Jupiter Orbiting the Subgiant HD 185269
We report the detection of a Jupiter-mass planet in a 6.838 day orbit around
the 1.28 solar mass subgiant HD 185269. The eccentricity of HD 185269b (e =
0.30) is unusually large compared to other planets within 0.1 AU of their
stars. Photometric observations demonstrate that the star is constant to
+/-0.0001 mag on the radial velocity period, strengthening our interpretation
of a planetary companion. This planet was detected as part of our radial
velocity survey of evolved stars located on the subgiant branch of the H-R
diagram--also known as the Hertzsprung Gap. These stars, which have masses
between 1.2 and 2.5 solar masses, play an important role in the investigation
of the frequency of extrasolar planets as a function of stellar mass.Comment: 18 pages, 4 figures, 3 tables, ApJ in press (scheduled for Dec 2006,
v652n2
The NASA-UC Eta-Earth Program: III. A Super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785
We report the discovery of planets orbiting two bright, nearby early K dwarf
stars, HD 97658 and Gl 785. These planets were detected by Keplerian modelling
of radial velocities measured with Keck-HIRES for the NASA-UC Eta-Earth Survey.
HD 97658 b is a close-in super-Earth with minimum mass Msini = 8.2 +/- 1.2
M_Earth, orbital period P = 9.494 +/- 0.005 d, and an orbit that is consistent
with circular. Gl 785 b is a Neptune-mass planet with Msini = 21.6 +/- 2.0
M_Earth, P = 74.39 +/- 0.12 d, and orbital eccentricity 0.30 +/- 0.09.
Photometric observations with the T12 0.8 m automatic photometric telescope at
Fairborn Observatory show that HD 97658 is photometrically constant at the
radial velocity period to 0.09 mmag, supporting the existence of the planet.Comment: Submitted to ApJ, 7 pages, 6 figures, 5 table
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