1,771 research outputs found
The milliped genus Euryurus Koch, 1847 (Polydesmida: Euryuridae) west of the Mississippi River; occurrence of E. leachii (Gray, 1832) on Crowley’s Ridge, Arkansas
The milliped genus Euryurus Koch, 1847, and the species, E. leachii (Gray, 1832) (Polydesmida: Euryuridae), are recorded from three sites on the northern part of Crowley’s Ridge (Cross, Lee, and Poinsett counties), Arkansas, where the only prior familial records are of Auturus evides (Bollman, 1887). Coupled with the published locality of E. leachii in Phillips Co., at the southern extremity of the Ridge, the only known occurrences of both the genus and species in Arkansas and west of the Mississippi River are in this physiographic feature. The Arkansas population is geographically peripheral but anatomically intermediate between the two recognized subspecies, E. l. leachii and E. l. fraternus Hoffman, 1978, and we do not assign it to a race. Molecular investigations seem necessary to resolve relationships in the “E. leachii complex.
Congress and Deregulation: Federal Legislative Issues Past, Present and Future.
I am Bill Robinson, and I am pinch-hitting for Mark La Fratta. Mark did something that caused him to have to go to Gary, I am not sure what it is. Perhaps, Mr. Brown will be able to tell us later on. In any event, it is a pleasure to be here. A couple of Saturdays ago, I was out sailing in an old boat I have, and we had wonderful winds. We were wasting in an area on the Rappahannock that I was not very familiar with, and we were just about to make our last tide in the fifth of six legs of the race, when we ran aground so badly, and so far, that it looked like one of those photographs after a hurricane, with the boat keeled over. Eventually, somebody came by and yelled over from his boat, It sure is a lot easier standing up at a podium in a courtroom, than what you are doing, is it not, my boy. It was a bailiff in the Federal Judge\u27s Courtroom in Richmond, and the general proposition he used was correct. And, it is with a little trepidation that I come because you all are experts at this, and the panelists are certainly experts, and I am simply going to be introducing them
Two Jovian-Mass Planets in Earthlike Orbits
We report the discovery of two new planets: a 1.94 M_Jup planet in a 1.8-year
orbit of HD 5319, and a 2.51 M_Jup planet in a 1.1-year orbit of HD 75898. The
measured eccentricities are 0.12 for HD 5319 b and 0.10 for HD 75898 b, and
Markov Chain Monte Carlo simulations based on derived orbital parameters
indicate that the radial velocities of both stars are consistent with circular
planet orbits. With low eccentricity and 1 < a < 2 AU, our new planets have
orbits similar to terrestrial planets in the solar system. The radial velocity
residuals of both stars have significant trends, likely arising from substellar
or low-mass stellar companions.Comment: 32 pages, including 11 figures and 5 tables. Accepted by 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 cloud-in-cloud problem for non-Gaussian density fields
The cloud-in-cloud problem is studied in the context of the extension to
non-Gaussian density fields of the Press-Schechter approach for the calculation
of the mass function. As an example of a non-Gaussian probability distribution
functions (PDFs) we consider the Chi-square, with various degrees of freedom.
We generate density fields in cubic boxes with periodic boundary conditions and
then determine the number of points considered collapsed at each scale through
an hierarchy of smoothing windows. We find that the mass function we obtain
differs from that predicted using the Extended Press-Schechter formalism,
particularly for low values of and for those PDFs most distinct from a
Gaussian.Comment: 5 pages, LaTex using mn.sty, matches published version, results for
the Inverted Chi-square distribution withdraw
Vegetation response to invasive Tamarix control in southwestern U.S. rivers: a collaborative study including 416 sites
Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix less than active removal by mechanically using hand and chain-saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow-up treatments for Tamarix resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix-infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species
Retired A Stars and Their Companions. III. Comparing the Mass-Period Distributions of Planets Around A-Type Stars and Sun-Like Stars
We present an analysis of ~5 years of Lick Observatory radial velocity
measurements targeting a uniform sample of 31 intermediate-mass subgiants (1.5
< M*/Msun < 2.0) with the goal of measuring the occurrence rate of Jovian
planets around (evolved) A-type stars and comparing the distributions of their
orbital and physical characteristics to those of planets around Sun-like stars.
We provide updated orbital solutions incorporating new radial velocity
measurements for five known planet-hosting stars in our sample; uncertainties
in the fitted parameters are assessed using a Markov Chain Monte Carlo method.
The frequency of Jovian planets interior to 3 AU is 26 (+9,-8)%, which is
significantly higher than the ~5-10% frequency observed around solar-mass
stars. The median detection threshold for our sample includes minimum masses
down to {0.2, 0.3, 0.5, 0.6, 1.3} MJup within {0.1, 0.3, 0.6, 1.0, 3.0} AU. To
compare the properties of planets around intermediate-mass stars to those
around solar-mass stars we synthesize a population of planets based on the
parametric relationship dN ~ M^{alpha}P^{beta} dlnM dlnP, the observed planet
frequency, and the detection limits we derived. We find that the values of
alpha and beta for planets around solar-type stars from Cumming et al. fail to
reproduce the observed properties of planets in our sample at the 4 sigma
level, even when accounting for the different planet occurrence rates. Thus,
the properties of planets around A stars are markedly different than those
around Sun-like stars, suggesting that only a small (~ 50%) increase in stellar
mass has a large influence on the formation and orbital evolution of planets.Comment: Accepted by the Astrophysical Journal; 15 pages, 15 figure
The N2K Consortium. II. A Transiting Hot Saturn Around HD 149026 With a Large Dense Core
Doppler measurements from Subaru and Keck have revealed radial velocity
variations in the V=8.15, G0IV star HD 149026 consistent with a Saturn-Mass
planet in a 2.8766 day orbit. Photometric observations at Fairborn Observatory
have detected three complete transit events with depths of 0.003 mag at the
predicted times of conjunction. HD 149026 is now the second brightest star with
a transiting extrasolar planet. The mass of the star, based on interpolation of
stellar evolutionary models, is 1.3 +/- 0.1 solar masses; together with the
Doppler amplitude, K=43.3 m s^-1, we derive a planet mass Msin(i)=0.36 Mjup,
and orbital radius of 0.042 AU. HD 149026 is chromospherically inactive and
metal-rich with spectroscopically derived [Fe/H]=+0.36, Teff=6147 K, log g=4.26
and vsin(i)=6.0 km s^-1. Based on Teff and the stellar luminosity of 2.72 Lsun,
we derive a stellar radius of 1.45 Rsun. Modeling of the three photometric
transits provides an orbital inclination of 85.3 +/- 1.0 degrees and (including
the uncertainty in the stellar radius) a planet radius of 0.725 +/- 0.05 Rjup.
Models for this planet mass and radius suggest the presence of a ~67 Mearth
core composed of elements heavier than hydrogen and helium. This substantial
planet core would be difficult to construct by gravitational instability.Comment: 25 pages, 5 figures, accepted by the Astrophysical Journa
The HARPS search for southern extrasolar planets XXI. Three new giant planets orbiting the metal-poor stars HD5388, HD181720, and HD190984
We present the discovery of three new giant planets around three
metal-deficient stars: HD5388b (1.96M_Jup), HD181720b (0.37M_Jup), and
HD190984b (3.1M_Jup). All the planets have moderately eccentric orbits (ranging
from 0.26 to 0.57) and long orbital periods (from 777 to 4885 days). Two of the
stars (HD181720 and HD190984) were part of a program searching for giant
planets around a sample of ~100 moderately metal-poor stars, while HD5388 was
part of the volume-limited sample of the HARPS GTO program. Our discoveries
suggest that giant planets in long period orbits are not uncommon around
moderately metal-poor stars.Comment: Accepted for publication in A&A (replaced by version with minor
language corrections
The California Planet Survey. I. Four New Giant Exoplanets
We present precise Doppler measurements of four stars obtained during the past decade at Keck Observatory by the California Planet Survey (CPS). These stars, namely, HD 34445, HD 126614, HD 13931, and Gl 179, all show evidence for a single planet in Keplerian motion. We also present Doppler measurements from the Hobby-Eberly Telescope (HET) for two of the stars, HD 34445 and Gl 179, that confirm the Keck detections and significantly refine the orbital parameters. These planets add to the statistical properties of giant planets orbiting near or beyond the ice line, and merit follow-up by astrometry, imaging, and space-borne spectroscopy. Their orbital parameters span wide ranges of planetary minimum mass (M sin i = 0.38-1.9 M(Jup)), orbital period (P = 2.87-11.5 yr), semimajor axis (a = 2.1-5.2 AU), and eccentricity (e = 0.02-0.41). HD 34445 b (P = 2.87 yr, M sin i = 0.79 MJup, e = 0.27) is a massive planet orbiting an old, G-type star. We announce a planet, HD 126614 Ab, and an M dwarf, HD 126614 B, orbiting the metal-rich star HD 126614 (which we now refer to as HD 126614 A). The planet, HD 126614 Ab, has minimum mass M sin i = 0.38 MJup and orbits the stellar primary with period P = 3.41 yr and orbital separation a = 2.3 AU. The faint M dwarf companion, HD 126614 B, is separated from the stellar primary by 489 mas (33 AU) and was discovered with direct observations using adaptive optics and the PHARO camera at Palomar Observatory. The stellar primary in this new system, HD 126614 A, has the highest measured metallicity ([ Fe/ H] = + 0.56) of any known planet-bearing star. HD 13931 b (P = 11.5 yr, M sin i = 1.88 MJup, e = 0.02) is a Jupiter analog orbiting a near solar twin. Gl 179 b (P = 6.3 yr, M sin i = 0.82 M(Jup), e = 0.21) is a massive planet orbiting a faint M dwarf. The high metallicity of Gl 179 is consistent with the planet-metallicity correlation among M dwarfs, as documented recently by Johnson & Apps.NSF AST-0702821NASA NNX06AH52GMcDonald Observator
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