299 research outputs found
The subgiant branch of omega Cen seen through high-resolution spectroscopy. II. The most metal-rich population
We analyze spectra of 18 stars belonging to the faintest subgiant branch in
omega Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution o R~17000
and a S/N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni,
Si, and Ti and we find that these stars have =-0.73 +/- 0.14 dex,
similarly to the corresponding red giant branch population (the RGB-a). We also
measure =+0.40 +/- 0.16 dex, and =+0.87 +/- 0.23 dex, in
general agreement with past studies. It is very interesting to note that we
found a uniform Al abundance, =+0.32 +/- 0.14 dex, for all the 18
SGB-a stars analysed here, thus supporting past evidence that the usual
(anti-)correlations are not present in this population, and suggesting a non
globular cluster-like origin of this particular population. In the dwarf galaxy
hypothesis for the formation of omega Cen, this population might be the best
candidate for the field population of its putative parent galaxy, although some
of its properties appear contradictory. It has also been suggested that the
most metal-rich population in omega Cen is significantly enriched in helium. If
this is true, the traditional abundance analysis techniques, based on model
atmospheres with normal helium content, might lead to errors. We have computed
helium enhanced atmospheres for three stars in our sample and verified that the
abundance errors due to the use of non-enhanced atmospheres are negligible.
Additional, indirect support to the enhanced helium content of the SGB-a
population comes from our Li upper limits.Comment: 11 pages, 5 figures, accepted for publication in A&
Formation of Multiple Populations in Globular Clusters: Another Possible Scenario
While chemical composition spreads are now believed to be a universal
characteristic of globular clusters (GCs), not all of them present multiple
populations in their color-magnitude diagrams (CMDs). Here we present a new
scenario for the formation of GCs, in an attempt to qualitatively explain this
otherwise intriguing observational framework. Our scenario divides GCs into
three groups, depending on the initial mass (M_I) of the progenitor structure
(PS), as follows. i) Massive PSs can retain the gas ejected by massive stars,
including the ejecta of core-collapse SNe. ii) Intermediate-mass PSs can retain
at least a fraction of the fast winds of massive stars, but none of the
core-collapse SNe ejecta. iii) Low-mass PSs can only retain the slow winds of
intermediate-mass stars. Members of the first group would include omega
Centauri (NGC 5139), M54 (NGC 6715), M22 (NGC 6656), and Terzan 5, whereas NGC
2808 (and possibly NGC 2419) would be members of the second group. The
remaining GCs which only present a spread in light elements, such as O and Na,
would be members of the third group. According to our scenario, the different
components in omega Cen should not display a sizeable spread in age. We argue
that this is consistent with the available observations. We give other simple
arguments in favor of our scenario, which can be described in terms of two main
analytical relations: i) Between the actual observed ratio between first and
second generation stars (R_SG^FG) and the fraction of first generation stars
that have been lost by the GC (S_L); and ii) Between S_L and M_I. We also
suggest a series of future improvements and empirical tests that may help
decide whether the proposed scenario properly describes the chemical evolution
of GCs.Comment: Accepted for publication in Astronomy and Astrophysic
: Probing the Milky Way and Magellanic Clouds potentials with the 6-D map of the Orphan-Chenab stream
We present a 6-D map of the Orphan-Chenab (OC) stream by combining the data
from 5 years of Southern Stellar Stream Spectroscopic Survey observations
with Gaia EDR3 data. We reconstruct the proper motion, radial velocity,
distance and on-sky track of stream stars with spline models and extract the
stellar density along the stream. The stream has a total luminosity of
and an average metallicity of , similar to classical MW
satellites like Draco. The stream shows drastic changes in its physical width
varying from 200 pc to 1 kpc, a constant line of sight velocity dispersion of 5
km/s, but an increase in the velocity dispersion along the stream near
pericenter to 10 km/s. Despite the large apparent variation in the
stellar number density along the stream, the flow rate of stars along the
stream is remarkably constant. We model the 6-D stream track by a
Lagrange-point stripping method with a flexible MW potential in the presence of
a moving extended LMC potential. This allows us to constrain the mass profile
of the MW within the distance range 15.6 < r < 55.5 kpc, with the best measured
enclosed mass of within 32.4 kpc. With
the OC stream's closest approach distance to the LMC of kpc, our
stream measurements are highly sensitive to the LMC mass profile with the most
precise measurement of the LMC's enclosed mass being at 32.8 kpc with
. We confidently detect that the LMC
DM halo extends to at least 53 kpc. The fitting of the OC stream allows us to
constrain the past LMC trajectory and the degree of dynamical friction it
experienced. We demonstrate that the stars on the OC stream show large energy
and angular momentum spreads caused by the LMC perturbation and revealing the
limitations of orbital invariants for substructure identification in the MW
halo.Comment: submitted to MNRAS; comments welcome; data released with the paper is
available on Zenodo https://zenodo.org/record/722265
Abundance analysis of the outer halo globular cluster Palomar 14
We determine the elemental abundances of nine red giant stars belonging to
Palomar 14 (Pal 14). Pal 14 is an outer halo globular cluster (GC) at a
distance of \sim 70 kpc. Our abundance analysis is based on high-resolution
spectra and one-dimensional stellar model atmospheres.We derived the abundances
for the iron peak elements Sc, V, Cr, Mn, Co, Ni, the {\alpha}-elements O, Mg,
Si, Ca, Ti, the light odd element Na, and the neutron-capture elements Y, Zr,
Ba, La, Ce, Nd, Eu, Dy, and Cu. Our data do not permit us to investigate light
element (i.e., O to Mg) abundance variations. The neutron-capture elements show
an r-process signature. We compare our measurements with the abundance ratios
of inner and other outer halo GCs, halo field stars, GCs of recognized
extragalactic origin, and stars in dwarf spheroidal galaxies (dSphs). The
abundance pattern of Pal 14 is almost identical to those of Pal 3 and Pal 4,
the next distant members of the outer halo GC population after Pal 14. The
abundance pattern of Pal 14 is also similar to those of the inner halo GCs,
halo field stars, and GCs of recognized extragalactic origin, but differs from
what is customarily found in dSphs field stars. The abundance properties of Pal
14 as well as those of the other outer halo GCs are thus compatible with an
accretion origin from dSphs. Whether or not GC accretion played a role, it
seems that the formation conditions of outer halo GCs and GCs in dSphs were
similar.Comment: 19 pages, 15 figures. Accepted by A&
Cultural differences in postnatal quality of life among German-speaking women - a prospective survey in two countries.
Assessment of quality of life after childbirth is an important health-outcome measurement for new mothers and is of special interest in midwifery. The Mother-Generated Index (MGI) is a validated instrument to assess postnatal quality of life. The tool has not been applied for making a cross-cultural comparison before. This study investigated (a) responses to the MGI in German-speaking women in Germany and Switzerland; and (b) associations between MGI scores on the one hand and maternity and midwifery care on the other
The potential of behavioural activation for the treatment of chronic pain: An exploratory review
Background: A substantial proportion of the population have a persistent pain condition. In addition to considerable personal suffering, these conditions have a massive economic cost at a society level in terms of health expenditure and lost productivity. To address this immense public health problem, treatment approaches are needed that are based on scientifically supported theories and that are easy to disseminate and scalable. Method: An exploratory qualitative review of literature concerning the operant model of chronic pain, related psychological interventions, and a synopsis of existing intervention studies with a behavioural activation (BA) approach was undertaken. Results: Current treatments for chronic pain are multimodal, however early research showed promising results for operant-based behavioural intervention alone. Although originally developed for depression, BA is a good theoretical match for operant conceptions of chronic pain. Further, because of its relative simplicity, BA is appealing in terms of its potential ease of dissemination. Two case studies have used BA for individuals suffering from fibromyalgia and produced promising treatment outcomes. Conclusions: Further research investigating the efficacy of BA for chronic pain is justified. Such work should begin with more single subject experimental designs to explore how BA might be best applied and the generalisability of the approach
Signature of a massive rotating metal-poor star imprinted in the Phoenix stellar stream*
The Phoenix stellar stream has a low intrinsic dispersion in velocity and
metallicity that implies the progenitor was probably a low mass globular
cluster. In this work we use Magellan/MIKE high-dispersion spectroscopy of
eight Phoenix stream red giants to confirm this scenario. In particular, we
find negligible intrinsic scatter in metallicity () and a large peak-to-peak range in [Na/Fe] and [Al/Fe]
abundance ratios, consistent with the light element abundance patterns seen in
the most metal-poor globular clusters. However, unlike any other globular
cluster, we also find an intrinsic spread in [Sr II/Fe] spanning 1 dex,
while [Ba II/Fe] shows nearly no intrinsic spread (). This abundance signature is best interpreted as
slow neutron capture element production from a massive fast-rotating metal-poor
star (, ,
). The low inferred cluster mass suggests the system
would have been unable to retain supernovae ejecta, implying that any massive
fast-rotating metal-poor star that enriched the interstellar medium must have
formed and evolved before the globular cluster formed. Neutron capture element
production from asymptotic giant branch stars or magneto-rotational
instabilities in core-collapse supernovae provide poor fits to the
observations. We also report one Phoenix stream star to be a lithium-rich giant
(). At it is among the
most metal-poor lithium-rich giants known.Comment: Accepted to ApJ 2021-07-0
Multiple Populations and a CH Star Found in the 300S Globular Cluster Stellar Stream
Milky Way globular clusters (GCs) display chemical enrichment in a phenomenon
called multiple stellar populations (MSPs). While the enrichment mechanism is
not fully understood, there is a correlation between a cluster's mass and the
fraction of enriched stars found therein. However, present-day GC masses are
often smaller than their masses at the time of formation due to dynamical mass
loss. In this work, we explore the relationship between mass and MSPs using the
stellar stream 300S. We present the chemical abundances of eight red giant
branch member stars in 300S with high-resolution spectroscopy from
Magellan/MIKE. We identify one enriched star characteristic of MSPs and no
detectable metallicity dispersion, confirming that the progenitor of 300S was a
globular cluster. The fraction of enriched stars (12.5\%) observed in our 300S
stars is less than the 50\% of stars found enriched in Milky Way GCs of
comparable present-day mass (\msun). We calculate the mass of
300S's progenitor and compare it to the initial masses of intact GCs, finding
that 300S aligns well with the trend between the system mass at formation and
enrichment. 300S's progenitor may straddle the critical mass threshold for the
formation of MSPs and can therefore serve as a benchmark for the stellar
enrichment process. Additionally, we identify a CH star, with high abundances
of \textit{s}-process elements, probably accreted from a binary companion. The
rarity of such binaries in intact GCs may imply stellar streams permit the
survival of binaries that would otherwise be disrupted.Comment: 15 pages, 7 tables, 8 figures. Accepted for publication in MNRA
Multiple Populations and a CH Star Found in the 300S Globular Cluster Stellar Stream
Milky Way globular clusters (GCs) display chemical enrichment in a phenomenon called multiple stellar populations (MSPs). While the enrichment mechanism is not fully understood, there is a correlation between a clusterâs mass and the fraction of enriched stars found therein. However, present-day GC masses are often smaller than their masses at the time of formation due to dynamical mass loss. In this work, we explore the relationship between mass and MSPs using the stellar stream 300S. We present the chemical abundances of eight red giant branch member stars in 300S with high-resolution spectroscopy fromMagellan/MIKE. We identify one enriched star characteristic of MSPs and no detectable metallicity dispersion, confirming that the progenitor of 300S was a globular cluster. The fraction of enriched stars (12.5%) observed in our 300S stars is less than the 50% of stars found enriched in Milky Way GCs of comparable present-day mass (⌠104.5 Mâ). We calculate the mass of 300Sâsprogenitor and compare it to the initial masses of intact GCs, finding that 300S aligns well with the trend between the system mass at formation and enrichment. 300Sâs progenitor may straddle the critical mass threshold for the formation of MSPs and can therefore serve as a benchmark for the stellar enrichment process. Additionally, we identify a CH star, with high abundancesof s-process elements, probably accreted from a binary companion. The rarity of such binaries in intact GCs may imply stellar streams permit the survival of binaries that would otherwise be disrupted
Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters. I. CH and CN band strength variations
Globular clusters show abundance variations for light elements that are not
yet well understood. The preferred explanation involves a self-enrichment
scenario, with two subsequent generations of stars. Observations of main
sequence stars allow us to investigate the signature of this chemically
processed material without the complicating effects of internal mixing. Our
goal is to investigate the C-N anti-correlation with low-resolution
spectroscopy of 20-50 stars fainter than the first dredge-up in seven globular
clusters (NGC288, NGC1851, NGC5927, NGC6352, NGC6388, and Pal12) with different
properties. We complemented our observations with 47~Tuc archival data, with
four additional clusters from the literature (M15, M22, M55, NGC362), and with
additional literature data on NGC288. In this first paper, we measured the
strength of CN and CH band indices, and we investigated the anti-correlation
and bimodality of these indices. We compared r_CN, the ratio of stars belonging
to the CN-strong and weak groups, with 15 different cluster parameters. We
clearly see bimodal anti-correlation of the CH and CN band stregths in the
metal-rich clusters (Pal12, 47Tuc, NGC6352, NGC5927). Only M15 among the
metal-poor clusters shows a clearly bimodal anti-correlation. We found weak
correlations (sligthly above 1 sigma) of r_CN with the cluster orbital
parameters, present-day total mass, cluster concentration, and age. Our
findings support the self-enrichment scenario, and suggest that the occurrence
of more than two major generations of stars in a GGC should be rare. Small
additional generations (<10-20% of the total) would be difficult to detect with
our samples. The first generation, which corresponds to the CN-weak stars,
usually contains more stars than the second one (=0.82+/-0.29), as
opposed to results based on the Na-O anti-correlations.Comment: 18 pages, 10 figures, 1 electronic table, accepted for publication in
A&A (language edited version
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