405 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
Signatures of rocky planet engulfment in HAT-P-4. Implications for chemical tagging studies
Aims. To explore the possible chemical signature of planet formation in the
binary system HAT-P-4, by studying abundance vs condensation temperature Tc
trends. The star HAT-P-4 hosts a planet detected by transits while its stellar
companion does not have any detected planet. We also study the Lithium content,
which could shed light on the problem of Li depletion in exoplanet host stars.
Conclusions. The exoplanet host star HAT-P-4 is found to be ~0.1 dex more metal
rich than its companion, which is one of the highest differences in metallicity
observed in similar systems. This could have important implications for
chemical tagging studies, disentangling groups of stars with a common origin.
We rule out a possible peculiar composition for each star as lambda Boo, delta
Scuti or a Blue Straggler. The star HAT-P-4 is enhanced in refractory elements
relative to volatile when compared to its stellar companion. Notably, the
Lithium abundance in HAT-P-4 is greater than in its companion by ~0.3 dex,
which is contrary to the model that explains the Lithium depletion by the
presence of planets. We propose a scenario where, at the time of planet
formation, the star HAT-P-4 locked the inner refractory material in
planetesimals and rocky planets, and formed the outer gas giant planet at a
greater distance. The refractories were then accreted onto the star, possibly
due to the migration of the giant planet. This explains the higher metallicity,
the higher Lithium content, and the negative Tc trend detected. A similar
scenario was recently proposed for the solar twin star HIP 68468, which is in
some aspects similar to HAT-P-4. We estimate a mass of at least Mrock ~ 10
Mearth locked in refractory material in order to reproduce the observed Tc
trends and metallicity.Comment: 5 pages, 6 figures, A&A Letters accepte
Habitat use by smooth snakes on lowland heath managed using 'conservation grazing'
Heathland in the UK, and parts of mainland Europe, is being managed increasingly by landowners and statutory conservation bodies e.g., Natural England, using cattle grazing which is often referred to as 'conservation grazing' in an attempt to justify its use in the absence of any detailed prior research into its actual benefits for wildlife species whose individual habitat requirements are likely to vary. Over four years, between 2010 and 2013, cattle were excluded from six hectares of lowland heath that had been subject to annual summer cattle grazing between May 1997 and autumn 2009 and in which reptile numbers had been monitored annually since 1997. Changes in smooth snake (Coronella austriaca) numbers were recorded annually in the ungrazed area and in a four hectare area of heathland adjacent to it that continued to be grazed. The number of individual smooth snakes, and the total number of smooth snake captures, were significantly higher in the ungrazed heath than the grazed heath and were associated with increased habitat structure, resulting principally from tall heathers and grasses. The results of the study suggest that the use of cattle grazing as a management tool on lowland heath is detrimental to smooth snake populations and that their recovery, following the cessation of grazing, may take many years
The orientation of galaxy pairs with filamentary structures: dependence on morphology
Aims. With the aim of performing an analysis of the orientations of galaxy
pair systems with respect to the underlying large-scale structure, we study the
alignment between the axis connecting the pair galaxies and the host cosmic
filament where the pair resides. In addition, we analyze the dependence of the
amplitude of the alignment on the morphology of pair members as well as
filament properties. Methods. We build a galaxy pair catalog requiring r_p <
100\kpc and \Delta V < 500 \kms within redshift from the Sloan
Digital Sky Survey (SDSS). We divided the galaxy pair catalog taking into
account the morphological classification by defining three pair categories
composed by elliptical-elliptical (E-E), elliptical-spiral (E-S) and
spiral-spiral (S-S) galaxies. We use a previously defined catalog of filaments
obtained from SDSS and we select pairs located closer than 1\mpc from the
filament spine, which are considered as members of filaments. For these pairs,
we calculate the relative angle between the axis connecting each galaxy, and
the direction defined by the spine of the parent filament.
Results. We find a statistically significant alignment signal between the
pair axes and the spine of the host filaments consistent with a relative excess
of 15\% aligned pairs. We obtain that pairs composed by elliptical
galaxies exhibit a stronger alignment, showing a higher alignment signal for
pairs closer than 200 \kpc to the filament spine. In addition, we find that
the aligned pairs are associated with luminous host filaments populated with a
high fraction of elliptical galaxies.
The findings of this work show that large scale structures play a fundamental
role in driving galactic anisotropic accretion as induced by galaxy pairs
exhibiting a preferred alignment along the filament direction.Comment: 8 pages, 6 figures. Accepted for publication in A&
High-contrast imaging of HD 29992 and HD 196385 with GPI
Based on high contrast images obtained with the Gemini Planet Imager (GPI),
we report the discovery of two point-like sources at angular separations of
and from the stars HD 29992 and HD 196385. A
combined analysis of the new GPI observations and images from the literature
indicates that the source close to HD 29992 could be a companion to the star.
Concerning HD 196385, the small number of contaminants () suggests
that the detected source may be gravitationally bound to the star. For both
systems, we discarded the presence of other potential companions with
M at . From stellar model atmospheres and
low-resolution GPI spectra, we derive masses of - M
for these sources. Using a Markov-chain Monte Carlo approach, we performed a
joint fit of the new astrometry measurements and published radial velocity data
to characterize the possible orbits. For HD 196385B, the median dynamic mass is
in agreement with that derived from model atmospheres, whilst for HD 29992B,
the orbital fit favors masses close to the brown dwarf regime(
M). HD 29992 and HD 196385 might be two new binary systems with
M-type stellar companions. However, new high angular resolution images would
help to definitively confirm whether the detected sources are gravitationally
bound to their respective stars, and permit tighter constraints on the orbital
parameters of both systems
KIC~8975515: a fast-rotating ( Dor - Sct) hybrid star with Rossby modes and a slower Sct companion in a long-period orbit
{KIC~8975515 is a \emph{Kepler} double-lined spectroscopic binary system with
hybrid pulsations. Two components have similar atmospheric properties (T 7400~K), and one of them is a fast rotator ( versus
32 km/s). Our aim is to study the \emph {Kepler} light curve in great detail in
order to determine the frequencies of the pulsations, to search for regular
spacing patterns in the Fourier spectrum, if any, and to discuss their origin
in the context of binarity and fast rotation. In this paper, we study the
properties of the stellar pulsations based on a careful analysis in the low-,
intermediate- and high-frequency regions of the Fourier spectrum. This is done
by performing repeated frequency-search analyses with successive prewhitenings
of all the significant frequencies detected in the spectrum. Moreover, we
searched for regular period spacings among the modes, as well as frequency
splitting among the and modes. In the low-frequency regime, five
regular period spacing patterns including one series of prograde modes and
four series of retrograde modes were detected. The modes are
well-distributed with respect to the harmonics of the rotational frequency of
the fast-rotating star = 1.647 d. The dominant mode is
= 2.37 d. The strongest p mode, at = 13.97 d,
forms a singlet. In the high-frequency region, we identified two multiplets of
regularly split modes with mean frequency spacings of 0.42 d and
1.65 d. We detected some series of retrograde and prograde modes
as well as two multiplets of modes with frequency spacings related to the
stellar rotation of both components of the twin system KIC~8975515. We
identified the fast-rotating component as a hybrid pulsator with modes and
the slowly-rotating component as a Sct pulsator.Comment: Accepted to publish on A \&
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&
Innovative strategies to enhance the sensory quality of dry fermented sausages containing lactic ingredients by the addition of exogenous enzymes
This study investigated the impact of the addition of exogenous enzymes (Accelerzyme CPG, Debitrase DBP20) or cellular preparations (FlavoGard), traditionally used in the cheese industry, to accelerate flavour development of dry fermented sausages with 6% of lactic derivatives content. Sausages were fermented to pH 5.0, dried for 32 days and vacuum packed stored under refrigeration for 60 days. Sausages were analysed for physicochemical parameters, technological microbiota and proteolysis after fermentation, drying/ripening and storage. Similar compositional results were obtained in all products (38-39% humidity in the final product; 38.2% fat and 40.7% protein as dry matter throughout the study). Debitrase application positively affected proteolysis by changing the free amino acid profile and increasing non-protein nitrogen and total free amino acids by 2.2 and 11.8-fold, respectively. Accelerzyme increased ripened cheese flavour and overall sensory quality from 5.1 to 5.8; Debitrase increased ripened cheese odour and flavour, bitterness, umami, adhesiveness, pastiness, and overall sensory quality from 5.0 to 5.9, and decreased acid and hardness. This study highlights the effects of adding some exogenous enzyme/bacterial preparations traditionally used in the cheese industry to enhance the flavour of dry fermented sausages with high content of lactic ingredients and increase its sensory quality.info:eu-repo/semantics/acceptedVersio
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