579 research outputs found
Comparison of Intravenous Medetomidine and Medetomidine/Ketamine for Immobilization of Free-Ranging Variable Flying Foxes (Pteropus hypomelanus)
Medetomidine (0.03 mg/kg) and medetomidine/ketamine (0.05/5.0 and 0.025/2.5 mg/kg), administered by intravenous injection, were evaluated for short-term immobilization of wild-caught variable flying foxes (Pteropus hypomelanus). Medetomidine alone produced incomplete chemical restraint and a stressful, prolonged induction. Both ketamine/medetomidine doses produced a smooth induction and complete immobilization. The combined medetomidine/ketamine dose of 0.025/2.5 mg/kg produced a rapid induction (232±224 sec) with minimal struggling and vocalization, a complete and effective immobilization period, and tended to lead to a faster and better quality recovery than medetomidine alone or a higher dose of medetomidine and ketamine (0.05/5.0 mg/kg), thus reducing holding time and permitting an earlier release of the bat back into the wild
The Effect of Differential Limb Magnification on Abundance Analysis of Microlensed Dwarf Stars
Finite source effects can be important in observations of gravitational
microlensing of stars. Near caustic crossings, for example, some parts of the
source star will be more highly magnified than other parts. The spectrum of the
star is then no longer the same as when it is unmagnified, and measurements of
the atmospheric parameters and abundances will be affected. The accuracy of
abundances measured from spectra taken during microlensing events has become
important recently because of the use of highly magnified dwarf stars to probe
abundance ratios and the abundance distribution in the Galactic bulge. In this
paper, we investigate the effect of finite source effects on spectra by using
magnification profiles motivated by two events to synthesize spectra for dwarfs
between 5000K to 6200K at solar metallicity. We adopt the usual techniques for
analyzing the microlensed dwarfs, namely, spectroscopic determination of
temperature, gravity, and microturbulent velocity, relying on equivalent
widths. We find that ignoring the finite source effects for the more extreme
case results in errors in Teff < 45K, in log g of <0.1 dex and in
microturbulent velocity of <0.1 km/s. In total, changes in equivalent widths
lead to small changes in atmospheric parameters and changes in abundances of
<0.06 dex, with changes in [FeI/H] of <0.03 dex. For the case with a larger
source-lens separation, the error in [FeI/H] is <0.01 dex. This latter case
represents the maximum effect seen in events whose lightcurves are consistent
with a point-source lens, which includes the majority of microlensed bulge
dwarfs published so far.Comment: 11 pages, 11 figures, submitted to Ap
Testing the Asteroseismic Mass Scale Using Metal-Poor Stars Characterized with APOGEE and Kepler
Fundamental stellar properties, such as mass, radius, and age, can be
inferred using asteroseismology. Cool stars with convective envelopes have
turbulent motions that can stochastically drive and damp pulsations. The
properties of the oscillation frequency power spectrum can be tied to mass and
radius through solar-scaled asteroseismic relations. Stellar properties derived
using these scaling relations need verification over a range of metallicities.
Because the age and mass of halo stars are well-constrained by astrophysical
priors, they provide an independent, empirical check on asteroseismic mass
estimates in the low-metallicity regime. We identify nine metal-poor red giants
(including six stars that are kinematically associated with the halo) from a
sample observed by both the Kepler space telescope and the Sloan Digital Sky
Survey-III APOGEE spectroscopic survey. We compare masses inferred using
asteroseismology to those expected for halo and thick-disk stars. Although our
sample is small, standard scaling relations, combined with asteroseismic
parameters from the APOKASC Catalog, produce masses that are systematically
higher (=0.17+/-0.05 Msun) than astrophysical expectations. The
magnitude of the mass discrepancy is reduced by known theoretical corrections
to the measured large frequency separation scaling relationship. Using
alternative methods for measuring asteroseismic parameters induces systematic
shifts at the 0.04 Msun level. We also compare published asteroseismic analyses
with scaling relationship masses to examine the impact of using the frequency
of maximum power as a constraint. Upcoming APOKASC observations will provide a
larger sample of ~100 metal-poor stars, important for detailed asteroseismic
characterization of Galactic stellar populations.Comment: 4 figures; 1 table. Accepted to ApJ
Chemical Composition of Faint (I~21 mag) Microlensed Bulge Dwarf OGLE-2007-BLG-514S
We present a high-resolution spectrum of a microlensed G dwarf in the
Galactic bulge with spectroscopic temperature T_eff = 5600 +/- 180 K. This I~21
mag star was magnified by a factor ranging from 1160 to 1300 at the time of
observation. Its high metallicity ([Fe/H] = 0.33 +/- 0.15) places this star at
the upper end of the bulge giant metallicity distribution. Using a K-S test, we
find a 1.6% probability that the published microlensed bulge dwarfs share an
underlying distribution with bulge giants, properly accounting for a radial
bulge metallicity gradient. We obtain abundance measurements for 15 elements
and perform a rigorous error analysis that includes covariances between
parameters. This star, like bulge giants with the same metallicity, shows no
alpha enhancement. It confirms the chemical abundance trends observed in
previously analyzed bulge dwarfs. At supersolar metallicities, we observe a
discrepancy between bulge giant and bulge dwarf Na abundances.Comment: 13 pages, 8 figures, 5 tables, submitted to Ap
Validating New Summary Indices for the Childhood Trauma Interview: Associations with First Onsets of Major Depressive Disorder and Anxiety Disorders
Childhood and adolescent adversity is of great interest in relation to risk for psychopathology, and interview measures of adversity are thought to be more reliable and valid than their questionnaire counterparts. One interview measure, the Childhood Trauma Interview (CTI; Fink et al., 1995), has been positively evaluated relative to similar measures, but there are some psychometric limitations to an existing scoring approach that limit the full potential of this measure. We propose several new summary indices for the CTI that permit examination of different types of adversity and different developmental periods. Our approach creates several summary indices: one sums the severity scores of adversities endorsed; another utilizes the number of minor and major (moderate to severe) adversities. The new indices were examined in association with first onsets of major depressive disorder (MDD) and anxiety disorders across a 5-year period using annual clinical diagnostic interviews (Structured Clinical Interview for DSMâIVâTR). Summary scores derived with the previously used approach were also examined for comparison. Data on 332 participants came from the Youth Emotion Project, a longitudinal study of risk for emotional disorders. Results support the predictive validity of the proposed summary scoring methods and indicate that several forms of major (but typically not minor) adversity are significantly associated with first onsets of MDD and anxiety disorders. Finally, multivariate regression models show that, in many instances, the new indices contributed significant unique variance predicting disorder onsets over and above the previously used summary indices
Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars
A knowledge of stellar ages is crucial for our understanding of many
astrophysical phenomena, and yet ages can be difficult to determine. As they
become older, stars lose mass and angular momentum, resulting in an observed
slowdown in surface rotation. The technique of 'gyrochronology' uses the
rotation period of a star to calculate its age. However, stars of known age
must be used for calibration, and, until recently, the approach was untested
for old stars (older than 1 gigayear, Gyr). Rotation periods are now known for
stars in an open cluster of intermediate age (NGC 6819; 2.5 Gyr old), and for
old field stars whose ages have been determined with asteroseismology. The data
for the cluster agree with previous period-age relations, but these relations
fail to describe the asteroseismic sample. Here we report stellar evolutionary
modelling, and confirm the presence of unexpectedly rapid rotation in stars
that are more evolved than the Sun. We demonstrate that models that incorporate
dramatically weakened magnetic braking for old stars can---unlike existing
models---reproduce both the asteroseismic and the cluster data. Our findings
might suggest a fundamental change in the nature of ageing stellar dynamos,
with the Sun being close to the critical transition to much weaker magnetized
winds. This weakened braking limits the diagnostic power of gyrochronology for
those stars that are more than halfway through their main-sequence lifetimes.Comment: 25 pages, 3 figures in main paper, 6 extended data figures, 1 table.
Published in Nature, January 2016. Please see https://youtu.be/O6HzYgP5uyc
for a video description of the resul
Target Selection for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a
high-resolution infrared spectroscopic survey spanning all Galactic
environments (i.e., bulge, disk, and halo), with the principal goal of
constraining dynamical and chemical evolution models of the Milky Way. APOGEE
takes advantage of the reduced effects of extinction at infrared wavelengths to
observe the inner Galaxy and bulge at an unprecedented level of detail. The
survey's broad spatial and wavelength coverage enables users of APOGEE data to
address numerous Galactic structure and stellar populations issues. In this
paper we describe the APOGEE targeting scheme and document its various target
classes to provide the necessary background and reference information to
analyze samples of APOGEE data with awareness of the imposed selection criteria
and resulting sample properties. APOGEE's primary sample consists of ~100,000
red giant stars, selected to minimize observational biases in age and
metallicity. We present the methodology and considerations that drive the
selection of this sample and evaluate the accuracy, efficiency, and caveats of
the selection and sampling algorithms. We also describe additional target
classes that contribute to the APOGEE sample, including numerous ancillary
science programs, and we outline the targeting data that will be included in
the public data releases.Comment: Accepted to AJ. 31 pages, 11 figure
The APOKASC Catalog: An Asteroseismic and Spectroscopic Joint Survey of Targets in the Kepler Fields
We present the first APOKASC catalog of spectroscopic and asteroseismic
properties of 1916 red giants observed in the Kepler fields. The spectroscopic
parameters provided from the Apache Point Observatory Galactic Evolution
Experiment project are complemented with asteroseismic surface gravities,
masses, radii, and mean densities determined by members of the Kepler
Asteroseismology Science Consortium. We assess both random and systematic
sources of error and include a discussion of sample selection for giants in the
Kepler fields. Total uncertainties in the main catalog properties are of order
80 K in Teff , 0.06 dex in [M/H], 0.014 dex in log g, and 12% and 5% in mass
and radius, respectively; these reflect a combination of systematic and random
errors. Asteroseismic surface gravities are substantially more precise and
accurate than spectroscopic ones, and we find good agreement between their mean
values and the calibrated spectroscopic surface gravities. There are, however,
systematic underlying trends with Teff and log g. Our effective temperature
scale is between 0-200 K cooler than that expected from the Infrared Flux
Method, depending on the adopted extinction map, which provides evidence for a
lower value on average than that inferred for the Kepler Input Catalog (KIC).
We find a reasonable correspondence between the photometric KIC and
spectroscopic APOKASC metallicity scales, with increased dispersion in KIC
metallicities as the absolute metal abundance decreases, and offsets in Teff
and log g consistent with those derived in the literature. We present mean
fitting relations between APOKASC and KIC observables and discuss future
prospects, strengths, and limitations of the catalog data.Comment: 49 pages. ApJSupp, in press. Full machine-readable ascii files
available under ancillary data. Categories: Kepler targets, asteroseismology,
large spectroscopic survey
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