ABSTRACT
Using light curves with ∼3 min cadence and a duration of 2 h made using the OmegaWhite survey, we present the results of a search for short-period variable stars in the field of 20 open ...clusters. We identified 92 variable stars in these fields. Using a range of cluster member catalogues and Gaia EDR3 data, we have determined that 10 are cluster members and 2 more are probable members. Based on their position on the Gaia HRD and their photometric periods, we find that most of these are δ Sct stars. We obtained low-resolution optical spectroscopy of some of these cluster members and field stars. We discuss the cluster variable stars in the context of δ Sct stars in other open clusters.
The connection between helium-rich hot subdwarfs of spectral types O and B (He-sdB) has been relatively unexplored since the latter were found in significant numbers in the 1980s. In order to explore ...this connection further, we have analysed the surface composition of six He-sdB stars, including LB 1766, LB 3229, SB 21 (= Ton-S 137 = BPS 29503−0009), BPS 22940−0009, BPS 29496−0010 and BPS 22956−0094. Opacity-sampled line-blanketed model atmospheres have been used to derive atmospheric properties and elemental abundances. All the stars are moderately metal poor compared with the Sun (Fe/H≈−0.5). Four stars are nitrogen rich, two of these are carbon rich and at least four appear to be neon rich. The data are insufficient to rule out binarity in any of the sample. The surface composition and locus of the N-rich He-sdBs are currently best explained by the merger of two helium white dwarfs, or possibly by the merger of a helium white dwarf with a post-sdB white dwarf. C-rich He-sdBs require further investigation.
Plasminogen activator inhibitor-1 (PAI-1), a crucial regulator of fibrinolysis, is increased in sepsis, but its values in predicting disease severity or mortality outcomes have been controversial. ...Therefore, we conducted a systematic review and meta-analysis of its predictive values in sepsis.
PubMed and Embase were searched until August 18, 2017 for studies that evaluated the relationships between PAI-1 levels and disease severity or mortality in sepsis.
A total of 112 and 251 entries were retrieved from the databases, of which 18 studies were included in the final meta-analysis. A total of 4,467 patients (36% male, mean age: 62 years, mean follow-up duration: 36 days) were analyzed. PAI-1 levels were significantly higher in non-survivors than survivors odds ratios (OR): 3.93, 95% confidence interval (CI): 2.31-6.67,
< 0.0001 and in patients with severe sepsis than in those less severe sepsis (OR: 3.26, 95% CI: 1.37-7.75,
= 0.008).
PAI-1 is a significant predictor of disease severity and all-cause mortality in sepsis. Although the predictive values of PAI-1 reached statistical significance, the clinical utility of PAI-1 in predicting outcomes will require carefully designed prospective trials.
The aim of this study was to establish sex differences in remodeling and outcome in aortic stenosis (AS) and their associations with biomarkers of myocardial fibrosis.
The remodeling response and ...timing of symptoms is highly variable in AS, and sex plays an important role.
A total of 174 patients (133 men, mean age 66.2 ± 13.3 years) with asymptomatic moderate to severe AS underwent comprehensive stress cardiac magnetic resonance imaging, transthoracic echocardiography, and biomarker analysis (matrix metalloproteinase MMP-2, -3, -7, -8, and -9; tissue inhibitor matrix metalloproteinases-1 and -4; syndecan-1 and -4; and N-terminal pro-B-type natriuretic peptide), and were followed up at 6-month intervals. A primary endpoint was a composite of typical AS symptoms necessitating referral for aortic valve replacement, cardiovascular death, or major adverse cardiovascular events.
For a similar severity of AS, male patients demonstrated higher indexed left ventricular (LV) volumes and mass, more concentric remodeling (higher LV mass/volume), a trend to more late gadolinium enhancement (present in 51.1% men vs. 34.1% women; p = 0.057), and higher extracellular volume index than female patients (13.27 interquartile range (IQR): 11.5 to 17.0 vs. 11.53 IQR: 10.5 to 13.5 ml/m
, p = 0.017), with worse systolic and diastolic function and higher MMP-3 and syndecan-4 levels, whereas female patients had higher septal E/e'. Male sex was independently associated with indexed LV mass (β = 13.32 IQR: 9.59 to 17.05; p < 0.001). During median follow-up of 374 (IQR: 351 to 498) days, a primary outcome, driven by spontaneous symptom onset, occurred in 21.8% of male and 43.9% of female patients (relative risk: 0.50 95% confidence interval: 0.31 to 0.80; p = 0.004). Measures of AS severity were associated with the primary outcome in both sexes, whereas N-terminal pro-B-type natriuretic peptide, MMP-3, and mass/volume were only associated in men.
In AS, women tolerate pressure overload with less concentric remodeling and myocardial fibrosis but are more likely to develop symptoms. This may be related to higher wall stress and filling pressures in women.
The Southern African Large Telescope (SALT) survey of He-rich hot subdwarfs has identi-fied several binary candidates from variable or anomalous radial velocities, or unusually high rotational ...velocities. Many SALT survey objects have also been observed by the Transiting Exoplanet Survey Satellite (TESS). TESS light curves provide orbital periods and can also give clues about the nature of binary systems by distinguishing ellipsoidal variations from reflection effects. We present a summary of the candidate binary fraction within the SALT survey, as well as a breakdown of the identified candidates by spectral and helium class.
ABSTRACT
The Kepler spacecraft observed the hot subdwarf star PHL 417 during its extended K2 mission, and the high-precision photometric light curve reveals the presence of 17 pulsation modes with ...periods between 38 and 105 min. From follow-up ground-based spectroscopy, we find that the object has a relatively high temperature of 35 600 K, a surface gravity of $\log g / {\rm cm\, s^{-2}}\, =\, 5.75$ and a supersolar helium abundance. Remarkably, it also shows strong zirconium lines corresponding to an apparent +3.9 dex overabundance compared with the Sun. These properties clearly identify this object as the third member of the rare group of pulsating heavy-metal stars, the V366-Aquarii pulsators. These stars are intriguing in that the pulsations are inconsistent with the standard models for pulsations in hot subdwarfs, which predicts that they should display short-period pulsations rather than the observed longer periods. We perform a stability analysis of the pulsation modes based on data from two campaigns with K2. The highest amplitude mode is found to be stable with a period drift, $\dot{P}$, of less than 1.1 × 10−9 s s−1. This result rules out pulsations driven during the rapid stages of helium flash ignition.
Extreme helium stars are very rare low-mass supergiants in a late stage of evolution. They are probably contracting to become white dwarfs following a violent phase of evolution which caused them to ...become hydrogen-deficient giants, possibly R CrB stars. Using the latest generation of models for spherically expanding stellar atmospheres, we set out to measure mass-loss rates for a representative fraction of these stars. We have used high-resolution ultraviolet and optical spectra, and ultraviolet, optical and near-infrared photometry from a variety of archives. Overall atmospheric parameters have mostly been taken from previous analyses and checked for consistency. Mass-loss rates were measured by fitting the P Cygni and asymmetric profiles of C, N and Si ultraviolet resonance lines and lie in the range of 10−10–10−7 M⊙ yr−1. These rates follow a Castor-type () relation marking a lower limit for the mass loss from hot stars of all kinds. The mass-loss rates of the stars studied also show a strong correlation with their proximity to the Eddington limit. There is no firm evidence for variability in the stellar wind, although photospheric pulsations have been reported in many cases.
PG 1544+488 is an exceptional short-period spectroscopic binary containing two subdwarf B stars. It is also exceptional because the surfaces of both components are extremely helium-rich. We present a ...new analysis of spectroscopy of PG 1544+488 obtained with the William Herschel Telescope. We obtain improved orbital parameters and atmospheric parameters for each component. The orbital period P = 0.496 ± 0.002 d, dynamical mass ratio M.../M... = 0.911 ± 0.015 and spectroscopic radius ratio R.../R... = 0.939 ± 0.004 indicate a binary consisting of nearly identical twins. The data are insufficient to distinguish any difference in surface composition between the components, which are slightly metal-poor (1/3 solar) and carbon-rich (0.3 per cent by number). The latter indicates that the hotter component, at least, has ignited helium. The best theoretical model for the origin of PG 1544+488 is by the ejection of a common envelope from a binary system in which both components are giants with helium cores of nearly equal mass. Since precise tuning is necessary to yield two helium cores of similar masses at the same epoch, the mass ratio places very tight constraints on the dimensions of the progenitor system and on the physics of the common-envelope ejection mechanism. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
We report the discovery of three pulsating subdwarf B stars in binary systems observed with the Kepler space telescope during Campaign 5 of K2. EPIC 211696659 (SDSS J083603.98+155216.4) is a ...g-mode pulsator with a white dwarf companion and a binary period of 3.16 d. EPICs 211823779 (SDSS J082003.35+173914.2) and 211938328 (LB 378) are both p-mode pulsators with main-sequence F companions. The orbit of EPIC 211938328 is long (635 ± 146 d) while we cannot constrain that of EPIC 211823779. The p modes are near the Nyquist frequency and so we investigate ways to discriminate super- from sub-Nyquist frequencies. We search for rotationally induced frequency multiplets and all three stars appear to be slow rotators with EPIC 211696659 subsynchronous to its orbit.
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