283 research outputs found
KIC 9821622: An interesting lithium-rich giant in the Kepler field
We report the discovery of a new exceptional young lithium-rich giant, KIC
9821622, in the \textit{Kepler} field that exhibits an unusually large
enhancement of , Fe-peak, and \textit{r}-process elements. From
high-resolution spectra obtained with GRACES at Gemini North, we derived
fundamental parameters and detailed chemical abundances of 23 elements from
equivalent widths and synthesis analysis. By combining atmospheric stellar
parameters with available asteroseismic data, we obtained the stellar mass,
radius, and age. The data analysis reveals that KIC 9821622 is a Li-rich
(A(Li) = 1.80 0.2) intermediate-mass giant star ( = 1.64
) located at the red giant branch near the luminosity bump. We find
unexpectedly elevated abundances of Fe-peak and \textit{r}-process elements. In
addition, as previously reported, we find that this is a young star (2.37 Gyr)
with unusually high abundances of -elements ([/Fe] = 0.31). The
evolutionary status of KIC 9821622 suggests that its Li-rich nature is the
result of internal fresh Li that is synthesized through the Cameron-Fowler
mechanism near the luminosity bump. However, its peculiar enhancement of
, Fe-peak, and \textit{r}-process elements opens the possibility of
external contamination by material enriched by a supernova explosion. Although
it is less likely, planet accretion cannot be ruled out.Comment: Letter, 6 pages, 3 figures, Accepted for publication in A&A. - Some
language editing include
NUEVA ESPECIE DEL GĂNERO COLAPTES (AVES, PICIFORMES) PARA EL PLEISTOCENO DE LA REGIĂN PAMPEANA, ARGENTINA
Resumen â En el presente artĂculo se describe un esqueleto relativamente completo de una nueva especie de Picidae (pĂĄjaros carpinteros) procedente de los alrededores de la localidad de Merlo, en la provincia de Buenos Aires, Argenâ tina. El holotipo proviene del Miembro JĂĄuregui, de edad Pleistoceno TardĂo temprano (75.000â30.000 años AP). Material adicional referido a este taxĂłn procede del Pleistoceno InferiorâMedio (1.200.000â400.000 AP) del sur de la provincia de Buenos Aires, y del Pleistoceno TardĂo (126.000â11.000 AP) de Uruguay. Estos ejemplares indican que la especie poseĂa una amplia distribuciĂłn geogrĂĄfica y temporal. El material esqueletario disponible fue comparado con otros Picidae, resultando en el reconocimiento de una nueva especie del gĂ©nero viviente Colaptes. El nuevo taxĂłn, aquĂ denominado Colaptes naroskyi sp. nov. Es de tamaño corporal notable, comparable a la especie de Picidae sudamericano de mayor tamaño: el Carpintero MagallĂĄnico (Campephilus magellanicus). Difiere de otras especies conocidas de Colaptes por tener el tibiotarso y tarsometatarso notablemente elongados, y el hĂșmero proporcionalmente corto y delgado. Sobre la base de la morfologĂa del miembro posterior, se infiere que el nuevo taxĂłn habrĂa poseĂdo hĂĄbitos mĂĄs caminadores que las especies vivientes que hoy en dĂa frecuentan la RegiĂłn Pampeana. Colaptes naroskyi sp. nov. constituye la primera paleospecie de la familia Picidae descripta para el continente sudamericano.Abstract â A new species of the genus Colaptes (Aves, Piciformes) from the Pleistocene of the Pampean Region, Argentina The present paper describes a nearly complete skeleton of a new species of Picidae (woodpeckers) found near Merlo, Buenos Aires province, Argentina. The holotype was found in EarlyâLate Pleistocene (75.000â30.000 years BP) beds of the JĂĄuregui Member. Additional reference material, which can be attributed to this species, coming from EarlyâMid Pleistocene (1.200.000â400.000 BP) beds of southern Buenos Aires province, and from Late Pleistocene (126.000â11.000 BP) beds from Uruguay indicates that this species had a large temporal and geographical distribution. The available skeletal material was compared with other species of woodpeckers. Based on these comparisons we conclude that the material corresponds to a new species of the living genus Colaptes. The new taxon, Colaptes naroskyi sp. nov., is notably large, comparable in size with the largest South American woodpecker, the Magellanic Woodpecker (Campephilus magellanicus). It differs from other known Colaptes in the very elongate tibiotarsus and tarsometatarsus, and in a proportionally short and slender humerus. On the basis of the posterior limb morphology, the new taxon may have possessed more terrestrial habits than the living species currently inhabiting the region. Colaptes naroskyi sp. nov. constitutes the first paleospecies of woodpecker described for the entire South American continent.
Revisiting the 16 Cygni planet host at unprecedented precision and exploring automated tools for precise abundances
The binary system 16 Cygni is key in studies of the planet-star chemical
composition connection, as only one of the stars is known to host a planet.
This allows us to better assess the possible influence of planet interactions
on the chemical composition of stars that are born from the same cloud and
thus, should have a similar abundance pattern. In our previous work, we found
clear abundance differences for elements with Z between both components
of this system, and a trend of these abundances as a function of the
condensation temperature (T), which suggests a spectral chemical
signature related to planet formation. In this work we show that our previous
findings are still consistent even if we include more species, like the
volatile N and neutron capture elements (Z 30). We report a slope with
T of dex K, that is good agreement
with both our previous work and recent results by Nissen and collaborators. We
also performed some tests using ARES and iSpec to automatic measure the
equivalent width and found T slopes in reasonable agreement with our
results as well. In addition, we determine abundances for Li and Be by spectral
synthesis, finding that 16 Cyg A is richer not only in Li but also in Be, when
compared to its companion. This may be evidence of planet engulfment,
indicating that the T trend found in this binary system may be a chemical
signature of planet accretion in the A component, rather than a imprint of the
giant planet rocky core formation on 16 Cyg B.Comment: 11 pages, 5 figures, accepted for publication in A&
Particle-Filtering-Based State-of-Health Estimation and End-of-Life Prognosis for Lithium-Ion Batteries at Operation Temperature
We present the implementation of a particle-filtering-based framework that estimates the State-of-Health (SOH) and predicts the End-of-Life (EOL) of Lithium-Ion batteries, efficiently incorporating variations of ambient temperature in the analysis. The proposed approach uses an empirical state-space model, in which inputs are explicitly defined as the average temperature of operation and the output of an external module that detects self-recharge phenomena, on the other hand the output is a function that relates the current SOH and temperature with the Usable Capacity in that cycle. In addition, this approach allows to deal with data losses and outliers. In order to correct erroneous initial conditions in state estimates, an Outer Feedback Correction Loop is implemented. Finally, this framework is validated using degradation data from four sources: experimental degradation data from two Li-Ion 18650 cells, accelerated degradation data openly provided by NASA Ames Research Center, and artificially generated degradation data at different ambient temperatures.We present the implementation of a particle-filtering-based framework that estimates the State-of-Health (SOH) and predicts the End-of-Life (EOL) of Lithium-Ion batteries, efficiently incorporating variations of ambient temperature in the analysis. The proposed approach uses an empirical state-space model, in which inputs are explicitly defined as the average temperature of operation and the output of an external module that detects self-recharge phenomena, on the other hand the output is a function that relates the current SOH and temperature with the Usable Capacity in that cycle. In addition, this approach allows to deal with data losses and outliers. In order to correct erroneous initial conditions in state estimates, an Outer Feedback Correction Loop is implemented. Finally, this framework is validated using degradation data from four sources: experimental degradation data from two Li-Ion 18650 cells, accelerated degradation data openly provided by NASA Ames Research Center, and artificially generated degradation data at different ambient temperatures
Fundamental stellar parameters of benchmark stars from CHARA interferometry. I. Metal-poor stars
Benchmark stars are crucial as validating standards for current as well as
future large stellar surveys of the Milky Way. However, the number of suitable
metal-poor benchmarks is currently limited. We aim to construct a new set of
metal-poor benchmarks, based on reliable interferometric effective temperature
() determinations and a homogeneous analysis with a desired
precision of in . We observed ten late-type metal-poor
dwarf and giants: HD2665, HD6755, HD6833, HD103095, HD122563, HD127243,
HD140283, HD175305, HD221170, and HD224930. Only three of the ten stars
(HD103095, HD122563, and HD140283) have previously been used as benchmarks. For
the observations, we used the high angular resolution optical interferometric
instrument PAVO at the CHARA array. We modelled angular diameters using 3D limb
darkening models and determined directly from the
Stefan-Boltzmann relation, with an iterative procedure to interpolate over
tables of bolometric corrections. Surface gravities () were estimated
from comparisons to Dartmouth stellar evolution model tracks. We collected
spectroscopic observations from the ELODIE and FIES spectrographs and estimated
metallicities () from a 1D non-LTE abundance analysis of
unblended lines of neutral and singly ionized iron. We inferred
to better than for five of the stars (HD103095, HD122563, HD127243,
HD140283, and HD224930). The of the other five stars are
reliable to between ; the higher uncertainty on the for
those stars is mainly due to their having a larger uncertainty in the
bolometric fluxes. We also determined and with
median uncertainties of and ,
respectively. These ten stars can, therefore, be adopted as a new, reliable set
of metal-poor benchmarks.Comment: 13 pages, 7 figures, 8 tables + 10 online tables, abstract shortened
to meet arXiv requirements, accepted in A&
J01020100-7122208::an accreted evolved blue straggler that wasn't ejected from a supermassive black hole
J01020100-7122208 is a star whose origin and nature still challenges us. It
was first believed to be a yellow super giant ejected from the Small Magellanic
Cloud, but it was more recently claimed to be a red giant accelerated by the
Milky Way's central black hole. In order to unveil its nature, we analysed
photometric, astrometric and high resolution spectroscopic observations to
estimate the orbit, age, and 16 elemental abundances. Our results show that
this star has a retrograde and highly-eccentric orbit,
. Correspondingly, it likely crossed the Galactic
disk at from the Galactic centre. We obtained a
spectroscopic mass and age of and Gyr
respectively. Its chemical composition is similar to the abundance of other
retrograde halo stars. We found that the star is enriched in europium, having
[Eu/Fe] = 0.93 0.24, and is more metal-poor than reported in the
literature, with [Fe/H] = -1.30 0.10. This information was used to
conclude that J01020100-7122208 is likely not a star ejected from the central
black of the Milky Way or from the Small Magellanic Cloud. Instead, we propose
that it is simply a halo star which was likely accreted by the Milky Way in the
distant past but its mass and age suggest it is probably an evolved blue
straggler.Comment: 17 pages, 9 Figures, accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Energy production in varying {\alpha} theories
Aims. On the basis the theoretical model proposed by Bekenstein for
{\alpha}'s variation, we analyze the equations that describe the energy
exchange between matter and both the electromagnetic and the scalar fields.
Methods. We determine how the energy flow of the material is modified by the
presence of a scalar field. We estimate the total magnetic energy of matter
from the "sum rules techniques". We compare the results with data obtained from
the thermal evolution of the Earth and other planets. Results. We obtain
stringent upper limits to the variations in {\alpha} that are comparable with
those obtained from atomic clock frequency variations. Conclusions. Our
constraints imply that the fundamental length scale of Bekenstein's theory "lB"
cannot be larger than Planck's length "lP"
Stellar parameters and chemical abundances of 223 evolved stars with and without planets
We present fundamental stellar parameters and chemical abundances for a
sample of 86 evolved stars with planets and for a control sample of 137 stars
without planets. The analysis was based on both high S/N and resolution echelle
spectra. The goals of this work are i) to investigate chemical differences
between stars with and without planets; ii) to explore potential differences
between the properties of the planets around giants and subgiants; and iii) to
search for possible correlations between these properties and the chemical
abundances of their host stars. In agreement with previous studies, we find
that subgiants with planets are, on average, more metal-rich than subgiants
without planets by ~ 0.16 dex. The [Fe/H] distribution of giants with planets
is centered at slightly subsolar metallicities and there is no metallicity
enhancement relative to the [Fe/H] distribution of giants without planets.
Furthermore, contrary to recent results, we do not find any clear difference
between the metallicity distributions of stars with and without planets for
giants with M > 1.5 Msun. With regard to the other chemical elements, the
analysis of the [X/Fe] distributions shows differences between giants with and
without planets for some elements, particularly V, Co, and Ba. Analyzing the
planet properties, some interesting trends might be emerging: i) multi-planet
systems around evolved stars show a slight metallicity enhancement compared
with single-planet systems; ii) planets with a 0.5 AU orbit
subgiants with [Fe/H] > 0 and giants hosting planets with a 1 AU
have [Fe/H] < 0; iii) higher-mass planets tend to orbit more metal-poor giants
with M < 1.5 Msun, whereas planets around subgiants seem to follow the
planet-mass metallicity trend observed on dwarf hosts; iv) planets orbiting
giants show lower orbital eccentricities than those orbiting subgiants and
dwarfs.Comment: 49 pages, 31 figures, Accepted for publication in A&A, abstract
shortened - corrected references, typos, acknowledgements include
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