261 research outputs found
Rapid Rotation of Low-Mass Red Giants Using APOKASC: A Measure of Interaction Rates on the Post-main-sequence
We investigate the occurrence rate of rapidly rotating (10 km
s), low-mass giant stars in the APOGEE-Kepler (APOKASC) fields with
asteroseismic mass and surface gravity measurements. Such stars are likely
merger products and their frequency places interesting constraints on stellar
population models. We also identify anomalous rotators, i.e. stars with 5 km
s10 km s that are rotating significantly faster
than both angular momentum evolution predictions and the measured rates of
similar stars. Our data set contains fewer rapid rotators than one would expect
given measurements of the Galactic field star population, which likely
indicates that asteroseismic detections are less common in rapidly rotating red
giants. The number of low-mass moderate (5-10 km s) rotators in our
sample gives a lower limit of 7% for the rate at which low-mass stars interact
on the upper red giant branch because single stars in this mass range are
expected to rotate slowly. Finally, we classify the likely origin of the rapid
or anomalous rotation where possible. KIC 10293335 is identified as a merger
product and KIC 6501237 is a possible binary system of two oscillating red
giants.Comment: 39 pages, 8 figures, 4 tables. Accepted for publication in the
Astrophysical Journal. For a brief video discussing key results from this
paper see http://youtu.be/ym_0nV7_YqI . The full table 1 is available at
http://www.astronomy.ohio-state.edu/~tayar/tab1_full.tx
Cannibals in the thick disk II -- Radial-velocity monitoring of the young alpha-rich stars
We report the results from new observations from a long-term radial velocity
monitoring campaign complemented with high resolution spectroscopy, as well as
new astrometry and seismology of a sample of 41 red giants from the third
version of APOKASC, which includes young alpha rich (YAR) stars. The aim is to
better characterize the YAR stars in terms of binarity fraction, mass,
abundance trends and kinematic properties. The radial velocities of HERMES,
APOGEE and Gaia were combined to determine the binary fraction among YAR stars.
In combination with their mass estimate, their evolutionary status, chemical
composition and kinematic properties, it allows to better constrain the nature
of these objects. We find that the frequency of binaries among over-massive
stars is not significantly different than that of the other stars in our
sample, but that the most massive YAR stars are indeed single, which has been
predicted by population synthesis models. Studying their [C/N], [C/Fe] and
[N/Fe] trends with mass, many over-massive stars do not follow the APOKASC
stars, favouring the scenario that most of them are product of mass transfer.
Our sample further includes two under-massive stars, with sufficiently low
masses so that these stars could not have reached the red giant phase without
significant mass loss. Both over-massive and under-massive stars might show
some anomalous APOGEE abundances such as N, Na, P, K and Cr, although higher
resolution optical spectroscopy might be needed to confirm these findings.
Considering the significant fraction of stars that are formed in pairs and the
variety of ways that make mass transfer possible, the diversity in properties
in terms of binarity and chemistry of the over-massive and under-massive stars
studied here implies that it is not safe to directly relate the mass of the YAR
stars with age and that most of these objects are likely not young.Comment: Submitted to A&A, comments welcome
Anthropometric and musculoskeletal assessment of patients with Marfan syndrome
CONTEXTUALIZAÇÃO: A Síndrome de Marfan (SM) é uma doença autossômica dominante do tecido conjuntivo que envolve os sistemas ocular, cardiovascular e musculoesquelético, causada por mutações no gene da fibrilina1, gerando flacidez nos ligamentos articulares, favorecendo a hipermobilidade articular e redução na contenção do crescimento ósseo.
OBJETIVOS: Avaliar as medidas antropométricas, alterações musculoesqueléticas e a frequência do tratamento fisioterapêutico nos pacientes com SM.
MÉTODOS: Participaram deste estudo 26 pacientes, sendo 17 do gênero feminino, com idade de 13,23±2,77 anos, massa corpórea de 51,5±24-68 Kg, altura de 1,70±1,40-1,81 m e envergadura de 1,73±0,12 cm, e nove do gênero masculino, com idade de 14,44±2,18, massa corpórea de 61,0±42-72 Kg, altura de 1,83±1,66-1,97 m e envergadura de 1,93±0,13. Foram obtidas medidas antropométricas, alterações ME de forma padronizada, sendo o pectus e a escoliose, por avaliação radiológica, e a angulação (â) da curva escoliótica, pelo método de Cobb; a aracnodactilia, pelo sinal do polegar e teste de Walker-Murdoch, e a dolicostenomelia, pela envergadura em relação à altura. Os pacientes responderam a um questionário quanto à participação em tratamento de fisioterapia.
RESULTADOS: Quando comparados com a estimativa brasileira, a massa corpórea e a altura apresentaram valores maiores no gênero feminino (p=0,001 e p<0,0005) e masculino (p=0,019 e p=0,0001). Das alterações musculoesqueléticas, encontrou-se pectus em 3 (11%), pectus e escoliose em 19 (73%), dolicostenomelia em 11 (42%) e aracnodactilia em 21(80%). Onze (42%) pacientes com SM já haviam realizado tratamento de fisioterapia.
CONCLUSÕES: As alterações antropométricas e musculoesqueléticas estão presentes na SM, e o tratamento fisioterapêutico é pouco frequente. ________________________________________________________________________________________________ ABSTRACTBACKGROUND: Marfan syndrome (MS) is an autosomic dominant condition of the connective tissue that involves the ocular, cardiovascular and musculoskeletal systems. MS is caused by mutations in the fibrillin-1 gene, leading to joint ligaments flaccidity, joint hypermobility and an overgrowth of the long bones.
OBJECTIVES: The aim of the present study was to assess anthropometry, musculoskeletal alterations and the prevalence of physical therapy treatments among patients with MS.
METHODS: Twenty-six patients were included in this study [17 females (age: 13.23±2.77 years; body mass 51.5±24-68 Kg; height 1.70±1.40-1.81 m; arm span: 1.73±0.12 m) and 9 males (age: 14.44±2.18; body mass: 61.0±42-72 Kg; height: 1.83±1.66-1.97 m; arm span: 1.93±0.13 m)]. Anthropometric measurements and musculoskeletal abnormalities were determined in a standardized fashion: pectus and scoliosis were assessed through radiography and angulation (â) of the scoliosis curve using the Cobb method; arachnodactyly was assessed through the thumb sign and Walker-Murdoch test and dolichostenomelia was assessed by arm span in relation to height. Patients also responded to a questionnaire addressing participation in physical therapy.
RESULTS: In comparison to values estimated for the Brazilian population, mass and height were greater among the patients with MS (females: p=0.001 e p<0.0005 e males p=0.019 e p=0.0001, respectively). The following musculoskeletal abnormalities were found: pectus in 3 patients (11%), pectus and scoliosis in 19 (73%), dolichostenomelia in 11 (42%) and arachnodactyly in 21 (80%). Eleven patients (42%) with MS had previously undergone physical therapy.
CONCLUSIONS: Patients with MS exhibit altered musculoskeleto and anthropometry and have infrequent physical therapy treatment
Target Selection for the SDSS-IV APOGEE-2 Survey
APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing
roughly 300,000 stars across the entire sky. It is the successor to APOGEE and
is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding
upon APOGEE's goals of addressing critical questions of stellar astrophysics,
stellar populations, and Galactic chemodynamical evolution using (1) an
enhanced set of target types and (2) a second spectrograph at Las Campanas
Observatory in Chile. APOGEE-2 is targeting red giant branch (RGB) and red
clump (RC) stars, RR Lyrae, low-mass dwarf stars, young stellar objects, and
numerous other Milky Way and Local Group sources across the entire sky from
both hemispheres. In this paper, we describe the APOGEE-2 observational design,
target selection catalogs and algorithms, and the targeting-related
documentation included in the SDSS data releases.Comment: 19 pages, 6 figures. Accepted to A
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
The APO-K2 Catalog: II. Accurate Stellar Ages for Red Giant Branch Stars across the Milky Way
We present stellar age determinations for 4661 red giant branch stars in the APO-K2 catalog, derived using mass estimates from K2 asteroseismology from the K2 Galactic Archaeology Program and elemental abundances from the Apache Point Galactic Evolution Experiment survey. Our sample includes 17 of the 19 fields observed by K2, making it one of the most comprehensive catalogs of accurate stellar ages across the Galaxy in terms of the wide range of populations spanned by its stars, enabling rigorous tests of Galactic chemical evolution models. Taking into account the selection functions of the K2 sample, the data appear to support the age−chemistry morphology of stellar populations predicted by both inside-out and late-burst scenarios. We also investigate trends in age versus stellar chemistry and Galactic position, which are consistent with previous findings. Comparisons against APOKASC-3 asteroseismic ages show agreement to within ∼3%. We also discuss offsets between our ages and spectroscopic ages. Finally, we note that ignoring the effects of α-enhancement on stellar opacity (either directly or with the Salaris metallicity correction) results in an ∼10% offset in age estimates for the most α-enhanced stars, which is an important consideration for continued tests of Galactic models with this and other asteroseismic age samples
The APO-K2 Catalog. I. 7,673 Red Giants with Fundamental Stellar Parameters from APOGEE DR17 Spectroscopy and K2-GAP Asteroseismology
We present a catalog of fundamental stellar properties for 7,673 evolved
stars, including stellar radii and masses, determined from the combination of
spectroscopic observations from the Apache Point Observatory Galactic Evolution
Experiment (APOGEE), part of the Sloan Digital Sky Survey IV (SDSS), and
asteroseismology from K2. The resulting APO-K2 catalog provides
spectroscopically derived temperatures and metallicities, asteroseismic global
parameters, evolutionary states, and asteroseismically-derived masses and
radii. Additionally, we include kinematic information from \textit{Gaia}. We
investigate the multi-dimensional space of abundance, stellar mass, and
velocity with an eye toward applications in Galactic archaeology. The APO-K2
sample has a large population of low metallicity stars (288 at [M/H]
1), and their asteroseismic masses are larger than astrophysical
estimates. We argue that this may reflect offsets in the adopted fundamental
temperature scale for metal-poor stars rather than metallicity-dependent issues
with interpreting asteroseismic data. We characterize the kinematic properties
of the population as a function of -enhancement and position in the
disk and identify those stars in the sample that are candidate components of
the \textit{Gaia-Enceladus} merger. Importantly, we characterize the selection
function for the APO-K2 sample as a function of metallicity, radius, mass,
, color, and magnitude referencing Galactic simulations and
target selection criteria to enable robust statistical inferences with the
catalog.Comment: 28 Pages, 14 Figures, 1 Table. Full table and selection function data
available at https://github.com/Jesstella/APO-K2. Submitted April 18th 2023
with AJ, awaiting revie
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
Confirming chemical clocks: asteroseismic age dissection of the Milky Way disc(s)
Investigations of the origin and evolution of the Milky Way disc have long relied on chemical and kinematic identifications of its components to reconstruct our Galactic past. Difficulties in determining precise stellar ages have restricted most studies to small samples, normally confined to the solar neighbourhood. Here, we break this impasse with the help of asteroseismic inference and perform a chronology of the evolution of the disc throughout the age of the Galaxy. We chemically dissect the Milky Way disc population using a sample of red giant stars spanning out to 2 kpc in the solar annulus observed by the Kepler satellite, with the added dimension of asteroseismic ages. Our results reveal a clear difference in age between the low- and high-α populations, which also show distinct velocity dispersions in the V and W components. We find no tight correlation between age and metallicity nor [α/Fe] for the high-α disc stars. Our results indicate that this component formed over a period of more than 2 Gyr with a wide range of [M/H] and [α/Fe] independent of time. Our findings show that the kinematic properties of young α-rich stars are consistent with the rest of the high-α population and different from the low-α stars of similar age, rendering support to their origin being old stars that went through a mass transfer or stellar merger event, making them appear younger, instead of migration of truly young stars formed close to the Galactic bar
Confirming chemical clocks: asteroseismic age dissection of the Milky Way disk(s)
Investigations of the origin and evolution of the Milky Way disk have long relied on chemical and kinematic identification of its components to reconstruct our Galactic past. Difficulties in determining precise stellar ages have restricted most studies to small samples, normally confined to the solar neighbourhood. Here we break this impasse with the help of asteroseismic inference and perform a chronology of the evolution of the disk throughout the age of the Galaxy. We chemically dissect the Milky Way disk population using a sample of red giant stars spanning out to 2~kpc in the solar annulus observed by the {\it Kepler} satellite, with the added dimension of asteroseismic ages. Our results reveal a clear difference in age between the low- and high- populations, which also show distinct velocity dispersions in the and components. We find no tight correlation between age and metallicity nor [/Fe] for the high- disk stars. Our results indicate that this component formed over a period of more than 2~Gyr with a wide range of [M/H] and [/Fe] independent of time. Our findings show that the kinematic properties of young -rich stars are consistent with the rest of the high- population and different from the low- stars of similar age, rendering support to their origin being old stars that went through a mass transfer or stellar merger event, making them appear younger, instead of migration of truly young stars formed close to the Galactic bar
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