288 research outputs found
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
Genetically Distinct Behavioral Modules Underlie Natural Variation in Thermal Performance Curves
Thermal reaction norms pervade organismal traits as stereotyped responses to temperature, a fundamental environmental input into sensory and physiological systems. Locomotory behavior represents an especially plastic read-out of animal response, with its dynamic dependence on environmental stimuli presenting a challenge for analysis and for understanding the genomic architecture of heritable variation. Here we characterize behavioral reaction norms as thermal performance curves for the nematode Caenorhabditis briggsae, using a collection of 23 wild isolate genotypes and 153 recombinant inbred lines to quantify the extent of genetic and plastic variation in locomotory behavior to temperature changes. By reducing the dimensionality of the multivariate phenotypic response with a function-valued trait framework, we identified genetically distinct behavioral modules that contribute to the heritable variation in the emergent overall behavioral thermal performance curve. Quantitative trait locus mapping isolated regions on Chromosome II associated with locomotory activity at benign temperatures and Chromosome V loci related to distinct aspects of sensitivity to high temperatures, with each quantitative trait locus explaining up to 28% of trait variation. These findings highlight how behavioral responses to environmental inputs as thermal reaction norms can evolve through independent changes to genetically distinct modular components of such complex phenotypes
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
Concentration‐dependent optical‐absorption coefficient in n‐type GaAs
The doping-dependent, near-band-edge optical-absorption coefficient CY(h v) was deduced from optical transmission measurements in n-type GaAs thin films. The selenium-doped films were grown by metalorganic chemical-vapor deposition and do ed to produce room-temperature electron concentrations from 1.3 x 10” to 3.8X 1018 cm- P . The transmission measurements covered photon energies between 1.35 and 1.7 eV and were performed on double heterostructures with the substrate removed by selective etching. The results show good qualitative agreement with previous studies and good quantitative agreement, except for the heavily doped samples. For na=3.8 X 10” cme3, a( 1.42 eV\u3e is approximately four times that reported by previous workers. Secondary-ion-mass spectrometry measurements on flms grown under differing conditions demonstrate that a(hv) is sensitive to electrically inactive dopants and supports the hypothesis that precipitates or compensation influenced previous measurements. These comprehensive results on high-quality, uncompensated material should prove useful for fundamental studies of optical transitions in n-type GaAs as well as for modeling optoelectronic devices
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
2FGL J0846.0+2820: A new neutron star binary with a giant secondary and variable -ray emission
We present optical photometric and spectroscopic observations of the likely
stellar counterpart to the unassociated \emph{Fermi}-Large Area Telescope (LAT)
-ray source 2FGL J0846.0+2820, selected for study based on positional
coincidences of optical variables with unassociated LAT sources. Using optical
spectroscopy from the SOAR telescope, we have identified a late-G giant in an
eccentric ( = 0.06) 8.133 day orbit with an invisible primary. Modeling the
spectroscopy and photometry together lead us to infer a heavy neutron star
primary of and a partially stripped giant secondary of . H emission is observed in some of the spectra, perhaps
consistent with the presence of a faint accretion disk. We find the
-ray flux of 2FGL J0846.0+2820 dropped substantially in mid-2009,
accompanied by an increased variation in the optical brightness, and since then
it has not been detected by \emph{Fermi}. The long period and giant secondary
are reminiscent of the -ray bright binary 1FGL J1417.7--4407, which
hosts a millisecond pulsar apparently in the final stages of the pulsar
recycling process. The discovery of 2FGL J0846.0+2820 suggests the
identification of a new subclass of millisecond pulsar binaries that are the
likely progenitors of typical field millisecond pulsars.Comment: 12 pages, 8 figures, 3 tables. Accepted for publication in Ap
The Transit Light Curve Project. V. System Parameters and Stellar Rotation Period of HD 189733
We present photometry of HD 189733 during eight transits of its close-in
giant planet, and out-of-transit photometry spanning two years. Using the
transit photometry, we determine the stellar and planetary radii and the
photometric ephemeris. Outside of transits, there are quasiperiodic flux
variations with a 13.4 day period that we attribute to stellar rotation. In
combination with previous results, we derive upper limits on the orbital
eccentricity, and on the true angle between the stellar rotation axis and
planetary orbit (as opposed to the angle between the projections of those axes
on the sky).Comment: Accepted for publication in AJ [21 pages]; minor change
Odor blocking of stress hormone responses
Scents have been employed for millennia to allay stress, but whether or how they might do so is largely unknown. Fear and stress induce increases in blood stress hormones controlled by hypothalamic corticotropin releasing hormone neurons (CRHNs). Here, we report that two common odorants block mouse stress hormone responses to three potent stressors: physical restraint, predator odor, and male-male social confrontation. One odorant inhibits restraint and predator odor activation of excitatory neurons upstream of CRHNs in the bed nucleus of the stria terminalis (BNSTa). In addition, both activate inhibitory neurons upstream of CRHNs in the hypothalamic ventromedial nucleus (VMH) and silencing of VMH inhibitory neurons hinders odor blocking of stress. Together, these findings indicate that odor blocking can occur via two mechanisms: (1) Inhibition of excitatory neurons that transmit stress signals to CRHNs and (2) activation of inhibitory neurons that act directly or indirectly to inhibit stressor activation of CRHNs
Characterizing the Cool KOIs. VI. H- and K-band Spectra of Kepler M Dwarf Planet-Candidate Hosts
We present H- and K-band spectra for late-type Kepler Objects of Interest
(the "Cool KOIs"): low-mass stars with transiting-planet candidates discovered
by NASA's Kepler Mission that are listed on the NASA Exoplanet Archive. We
acquired spectra of 103 Cool KOIs and used the indices and calibrations of
Rojas-Ayala et al. to determine their spectral types, stellar effective
temperatures and metallicities, significantly augmenting previously published
values. We interpolate our measured effective temperatures and metallicities
onto evolutionary isochrones to determine stellar masses, radii, luminosities
and distances, assuming the stars have settled onto the main-sequence. As a
choice of isochrones, we use a new suite of Dartmouth predictions that reliably
include mid-to-late M dwarf stars. We identify five M4V stars: KOI-961
(confirmed as Kepler 42), KOI-2704, KOI-2842, KOI-4290, and the secondary
component to visual binary KOI-1725, which we call KOI-1725 B. We also identify
a peculiar star, KOI-3497, which has a Na and Ca lines consistent with a dwarf
star but CO lines consistent with a giant. Visible-wavelength adaptive optics
imaging reveals two objects within a 1 arc second diameter; however, the
objects' colors are peculiar. The spectra and properties presented in this
paper serve as a resource for prioritizing follow-up observations and planet
validation efforts for the Cool KOIs, and are all available for download online
using the "data behind the figure" feature.Comment: Accepted for publication in the Astrophysical Journal Supplement
Series (ApJS). Data and table are available in the sourc
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