2,369 research outputs found
The California Planet Survey IV: A Planet Orbiting the Giant Star HD 145934 and Updates to Seven Systems with Long-Period Planets
We present an update to seven stars with long-period planets or planetary
candidates using new and archival radial velocities from Keck-HIRES and
literature velocities from other telescopes. Our updated analysis better
constrains orbital parameters for these planets, four of which are known
multi-planet systems. HD 24040 b and HD 183263 c are super-Jupiters with
circular orbits and periods longer than 8 yr. We present a previously unseen
linear trend in the residuals of HD 66428 indicative on an additional planetary
companion. We confirm that GJ 849 is a multi-planet system and find a good
orbital solution for the c component: it is a planet in a 15 yr
orbit (the longest known for a planet orbiting an M dwarf). We update the HD
74156 double-planet system. We also announce the detection of HD 145934 b, a planet in a 7.5 yr orbit around a giant star. Two of our stars, HD
187123 and HD 217107, at present host the only known examples of systems
comprising a hot Jupiter and a planet with a well constrained period yr,
and with no evidence of giant planets in between. Our enlargement and
improvement of long-period planet parameters will aid future analysis of
origins, diversity, and evolution of planetary systems.Comment: 16 pages, 13 figures. Accepted for publication in Ap
Nickel Exposure Reduces Enterobactin Production in Escherichia Coli
Escherichia coli is a well- studied bacterium that can be found in many niches, such as industrial wastewater, where the concentration of nickel can rise to low- millimolar levels. Recent studies show that nickel exposure can repress pyochelin or induce pyo-verdine siderophore production in Pseudomonas aueroginosa. Understanding the mo-lecular cross- talk between siderophore production, metal homeostasis, and metal toxicity in microorganisms is critical for designing bioremediation strategies for metal- contaminated sites. Here, we show that high- nickel exposure prolongs lag phase duration as a result of low- intracellular iron levels in E. coli. Although E. coli cells respond to low- intracellular iron during nickel stress by maintaining high expres-sion of iron uptake systems such as fepA, the demand for iron is not met due to a lack of siderophores in the extracellular medium during nickel stress. Taken together, these results indicate that nickel inhibits iron accumulation in E. coli by reducing the presence of enterobactin in the extracellular medium
Five planets and an independent confirmation of HD 196885Ab from Lick Observatory
We present time series Doppler data from Lick Observatory that reveal the
presence of long-period planetary companions orbiting nearby stars. The typical
eccentricity of these massive planets are greater than the mean eccentricity of
known exoplanets. HD30562b has Msini = 1.29 Mjup, with semi-major axis of 2.3
AU and eccentricity 0.76. The host star has a spectral type F8V and is metal
rich. HD86264b has Msini = 7.0 Mjup, arel = 2.86 AU, an eccentricity, e = 0.7
and orbits a metal-rich, F7V star. HD87883b has Msini = 1.78 Mjup, arel = 3.6
AU, e = 0.53 and orbits a metal-rich K0V star. HD89307b has Msini = 1.78 Mjup,
arel = 3.3 AU, e = 0.24 and orbits a G0V star with slightly subsolar
metallicity. HD148427b has Msini = 0.96 Mjup, arel = 0.93 AU, eccentricity of
0.16 and orbits a metal rich K0 subgiant. We also present velocities for a
planet orbiting the F8V metal-rich binary star, HD196885A. The planet has Msini
= 2.58 Mjup, arel = 2.37 AU, and orbital eccentricity of 0.48, in agreement
with the independent discovery by Correia et al. 2008.Comment: 12 figures, 8 tables, accepted Ap
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
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
Nickel Exposure Reduces Enterobactin Production in \u3cem\u3eEscherichia coli\u3c/em\u3e
Escherichia coli is a well- studied bacterium that can be found in many niches, such as industrial wastewater, where the concentration of nickel can rise to low- millimolar levels. Recent studies show that nickel exposure can repress pyochelin or induce pyo-verdine siderophore production in Pseudomonas aueroginosa. Understanding the mo-lecular cross- talk between siderophore production, metal homeostasis, and metal toxicity in microorganisms is critical for designing bioremediation strategies for metal- contaminated sites. Here, we show that high- nickel exposure prolongs lag phase duration as a result of low- intracellular iron levels in E. coli. Although E. coli cells respond to low- intracellular iron during nickel stress by maintaining high expres-sion of iron uptake systems such as fepA, the demand for iron is not met due to a lack of siderophores in the extracellular medium during nickel stress. Taken together, these results indicate that nickel inhibits iron accumulation in E. coli by reducing the presence of enterobactin in the extracellular medium.
Escherichia coli is a well- studied bacterium that can be found in many niches, such as industrial wastewater, where the concentration of nickel can rise to low-millimolar levels. Recent studies show that nickel exposure can repress pyochelin or induce pyo- verdine siderophore production inPseudomonas aueroginosa. Understanding the mo- lecular cross-talk between siderophore production, metal homeostasis, and metal toxicity in microorganisms is critical for designing bioremediation strategies for metal-contaminated sites. Here, we show that high-nickel exposure prolongs lag phase duration as a result of low- intracellular iron levels in E. coli. Although E. coli cells respond to low- intracellular iron during nickel stress by maintaining high expres- sion of iron uptake systems such as fepA, the demand for iron is not met due to a lack of siderophores in the extracellular medium during nickel stress. Taken together, these results indicate that nickel inhibits iron accumulation inE. coli by reducing the presence of enterobactin inthe extracellular mediu
The N2K Consortium VI: Doppler Shifts Without Templates and Three New Short-Period Planets
We present a modification to the iodine cell Doppler technique that
eliminates the need for an observed stellar template spectrum. For a given
target star, we iterate toward a synthetic template spectrum beginning with an
existing spectrum of a similar star. We then perturb the shape of this
first-guess template to match the program observation of the target star taken
through an iodine cell. The elimination of a separate template observation
saves valuable telescope time, a feature that is ideally suited for the
quick-look strategy employed by the ``Next 2000 Stars'' (N2K) planet search
program. Tests using Keck/HIRES spectra indicate that synthetic templates yield
a short-term precision of 3 m/s and a long-term, run-to-run precision of 5 m/s.
We used this new Doppler technique to discover three new planets: a 1.5 Mjup
planet in a 2.1375 d orbit around HD 86081; a 0.71 Mjup planet in circular,
26.73 d orbit around HD 224693; and a Saturn-mass planet in an 18.179 d orbit
around HD 33283. The remarkably short period of HD 86081b bridges the gap
between the extremely short-period planets detected in the OGLE survey and the
16 Doppler-detected hot jupiters (P < 15 d), which have an orbital period
distribution that piles up at about three days. We have acquired photometric
observations of two of the planetary host stars with the automated photometric
telescopes at Fairborn Observatory. HD 86081 and HD 224693 both lack detectable
brightness variability on their radial velocity periods, supporting
planetary-reflex motion as the cause of the radial velocity variability. HD
86081 shows no evidence of planetary transits in spite of a 17.6% transit
probability.Comment: 39 pages, 12 figures, 8 tables (ApJ Accepted
Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
The Kepler mission has discovered over 2500 exoplanet candidates in the first
two years of spacecraft data, with approximately 40% of them in candidate
multi-planet systems. The high rate of multiplicity combined with the low rate
of identified false-positives indicates that the multiplanet systems contain
very few false-positive signals due to other systems not gravitationally bound
to the target star (Lissauer, J. J., et al., 2012, ApJ 750, 131). False
positives in the multi- planet systems are identified and removed, leaving
behind a residual population of candidate multi-planet transiting systems
expected to have a false-positive rate less than 1%. We present a sample of 340
planetary systems that contain 851 planets that are validated to substantially
better than the 99% confidence level; the vast majority of these have not been
previously verified as planets. We expect ~2 unidentified false-positives
making our sample of planet very reliable. We present fundamental planetary
properties of our sample based on a comprehensive analysis of Kepler light
curves and ground-based spectroscopy and high-resolution imaging. Since we do
not require spectroscopy or high-resolution imaging for validation, some of our
derived parameters for a planetary system may be systematically incorrect due
to dilution from light due to additional stars in the photometric aperture.
None the less, our result nearly doubles the number of verified exoplanets.Comment: 138 pages, 8 Figures, 5 Tables. Accepted for publications in the
Astrophysical Journa
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