Abstract
The Be phenomenon is present in about 20 per cent of B-type stars. Be stars show variability on a broad range of time-scales, which in most cases is related to the presence of a ...circumstellar disc of variable size and structure. For this reason, a time-resolved survey is highly desirable in order to understand the mechanisms of disc formation, which are still poorly understood. In addition, a complete observational sample would improve the statistical significance of the study of stellar and disc parameters. The ‘Be Stars Observation Survey’ (BeSOS) is a survey containing reduced spectra obtained using the Pontifica Universidad Católica High Echelle Resolution Optical Spectrograph (PUCHEROS) with a spectral resolution of 17 000 in the range 4260–7300 Å. BeSOS's main objective is to offer consistent spectroscopic and time-resolved data obtained with one instrument. The user can download or plot the data and obtain stellar parameters directly from the website. We also provide a star-by-star analysis based on photometric, spectroscopic and interferometric data, as well as general information about the whole BeSOS sample. Recently, BeSOS led to the discovery of a new Be star HD 42167 and facilitated study of the V/R variation of HD 35165 and HD 120324, the steady disc of HD 110335 and the Be shell status of HD 127972. Optical spectra used in this work, as well as the stellar parameters derived, are available online at http://besos.ifa.uv.cl.
The circumstellar disk density distributions for a sample of 63 Be southern stars from the BeSOS survey were found by modeling their H emission line profiles. These disk densities were used to ...compute disk masses and disk angular momenta for the sample. Average values for the disk mass are 3.4 × 10−9 and 9.5 × 10−10 M for early (B0-B3) and late (B4-B9) spectral types, respectively. We also find that the range of disk angular momentum relative to the star is (150-200)J /M and (100-150)J /M , again for early- and late-type Be stars, respectively. The distributions of the disk mass and disk angular momentum are different between early- and late-type Be stars at a 1% level of significance. Finally, we construct the disk mass distribution for the BeSOS sample as a function of spectral type and compare it to the predictions of stellar evolutionary models with rapid rotation. The observed disk masses are typically larger than the theoretical predictions, although the observed spread in disk masses is typically large.
Objective
To compare fetal microchimerism (FMc) in pregnancies with uncomplicated vaginal delivery (VD) versus caesarean delivery (CD).
Design
Prospective cohort study.
Setting
University of ...Washington and Fred Hutchinson Cancer Research Center, USA.
Population
Women delivering singleton pregnancies without pertinent antenatal complications with uncomplicated deliveries (n = 36).
Methods
We collected maternal predelivery, postdelivery and umbilical cord blood for each mother–baby pair. Following maternal and fetal genotyping, FMc was measured with quantitative polymerase chain reaction assays targeting fetus‐specific polymorphisms. Quantification of FMc is expressed as genome equivalents (gEq) of fetal DNA/100 000 total gEq tested. FMc detection was evaluated by logistic regression while controlling for total number of cell equivalents tested and clinically relevant covariates. FMc concentrations were compared using negative binomial regression while controlling for the same covariates and predelivery FMc positivity.
Main outcome measure
Detection and concentration of FMc by mode of delivery.
Results
Twenty‐four mother–baby pairs had a VD and 12 had a CD. Postdelivery FMc detection was higher following CD than after VD (58.3% versus 16.7%, P = 0.02). After controlling for covariates, the likelihood of postdelivery FMc detection was almost nine‐fold higher after CD than VD (odds ratio 8.8, 95% CI 1.6–47.6; P = 0.01). With respect to postdelivery FMc concentration, the detection rate ratio for CD versus VD in the adjusted negative binomial regression model was 14.7 (95% CI 3.2–66.8; P = 0.001).
Conclusion
Postdelivery peripheral FMc detection and concentration are significantly higher after CD than after VD. As FMc is associated with long‐term maternal health, our findings suggest that the mode of delivery may impact this risk.
Tweetable
Greater fetal microchimerism found in maternal blood following caesarean delivery compared with vaginal delivery.
Tweetable
Greater fetal microchimerism found in maternal blood following caesarean delivery compared with vaginal delivery.
Context. To progress in the understanding of evolution of massive stars one needs to constrain the mass-loss and determine the phenomenon responsible for the ejection of matter an its reorganization ...in the circumstellar environment Aims. In order to test various mass-ejection processes, we probed the geometry and kinematics of the dust and gas surrounding the Ae supergiant HD 62623. Methods. We used the combined high spectral and spatial resolution offered by the VLTI/AMBER instrument. Thanks to a new multi-wavelength optical/IR interferometry imaging technique, we reconstructed the first velocity-resolved images with a milliarcsecond resolution in the infrared domain. Results. We managed to disentangle the dust and gas emission in the HD 62623 circumstellar disc. We measured the dusty disc inner rim, i.e. 6 mas, constrained the inclination angle and the position angle of the major-axis of the disc. We also measured the inner gaseous disc extension (2 mas) and probed its velocity field thanks to AMBER high spectral resolution. We find that the expansion velocity is negligible, and that Keplerian rotation is a favoured velocity field. Such a velocity field is unexpected if fast rotation of the central star alone is the main mechanism of matter ejection. Conclusions. As the star itself seems to rotate below its breakup-up velocity, rotation cannot explain the formation of the dense equatorial disc. Moreover, as the expansion velocity is negligible, radiatively driven wind is also not a suitable explanation to explain the disc formation. Consequently, the most probable hypothesis is that the accumulation of matter in the equatorial plane is due to the presence of the spectroscopic low mass companion.
Context. Be stars are rapid rotators surrounded by a gaseous disk envelope whose origin is still under debate. This envelope is responsible for observed emission lines and large infrared excess. ...Aims. To progress in the understanding of the physical processes involved in the disk formation, we estimate the disk parameters for a sample of Be stars and search for correlations between these parameters and stellar properties. Methods. We performed spectro-interferometric observations of 26 Be stars in the region of the Brγ line to study the kinematical properties of their disks through the Doppler effect. Observations were performed at the Paranal observatory with the VLTI/AMBER interferometer. This instrument provides high spectral (R ≃ 12 000) and high spatial (θmin = 4 mas) resolutions. Results. We modeled 18 Be stars with emission in the Brγ line. The disk kinematic is described by a quasi-Keplerian rotation law, with the exception of HD 28497 that presents a one-arm density-wave structure. Using a combined sample, we derived a mean value for the velocity ratio V̅/V̅c = 0.75 $\overline{V/V_{\rm{c}}}=0.75$V/Vc¯=0.75 (where Vc is the critical velocity), and found that rotation axes are probably randomly distributed in the sky. Disk sizes in the line component model are in the range of 2–13 stellar radii and do not correlate with the effective temperature or spectral type. However, we found that the maximum size of a stable disk correlates with the rotation velocity at the inner part of the disk and the stellar mass. Conclusions. We found that, on average, the Be stars of our combined sample do not rotate at their critical velocity. However, the centrifugal force and mass of the star defines an upper limit size for a stable disk configuration. For a given rotation, high-mass Be stars tend to have more compact disks than their low-mass counterparts. It would be interesting to follow up the evolution of the disk size in variable stars to better understand the formation and dissipation processes of their circumstellar disks.
Context. Variable B supergiants (BSGs) constitute a heterogeneous group of stars with complex photometric and spectroscopic behaviours. They exhibit mass-loss variations and experience different ...types of oscillation modes, and there is growing evidence that variable stellar winds and photospheric pulsations are closely related. Aims. To discuss the wind properties and variability of evolved B-type stars, we derive new stellar and wind parameters for a sample of 19 Galactic BSGs by fitting theoretical line profiles of H, He, and Si to the observed ones and compare them with previous determinations. Methods. The synthetic line profiles are computed with the non-local thermodynamic equilibrium (NLTE) atmosphere code FASTWIND, with a β-law for hydrodynamics. Results. The mass-loss rate of three stars has been obtained for the first time. The global properties of stellar winds of mid/late B supergiants are well represented by a β-law with β > 2. All stars follow the known empirical wind momentum–luminosity relationships, and the late BSGs show the trend of the mid BSGs. HD 75149 and HD 99953 display significant changes in the shape and intensity of the Hα line (from a pure absorption to a P Cygni profile, and vice versa). These stars have mass-loss variations of almost a factor of 2.8. A comparison among mass-loss rates from the literature reveals discrepancies of a factor of 1 to 7. This large variation is a consequence of the uncertainties in the determination of the stellar radius. Therefore, for a reliable comparison of these values we used the invariant parameter Qr. Based on this parameter, we find an empirical relationship that associates the amplitude of mass-loss variations with photometric/spectroscopic variability on timescales of tens of days. We find that stars located on the cool side of the bi-stability jump show a decrease in the ratio V∞∕Vesc, while their corresponding mass-loss rates are similar to or lower than the values found for stars on the hot side. Particularly, for those variable stars a decrease in V∞∕Vesc is accompanied by a decrease in Ṁ. Conclusions. Our results also suggest that radial pulsation modes with periods longer than 6 days might be responsible for the wind variability in the mid/late-type. These radial modes might be identified with strange modes, which are known to facilitate (enhanced) mass loss. On the other hand, we propose that the wind behaviour of stars on the cool side of the bi-stability jump could fit with predictions of the δ−slow hydrodynamics solution for radiation-driven winds with highly variable ionization.
Although low serum 25-hydroxyvitamin D (25(OH)D) and elevated serum parathyroid hormone (PTH) have been associated with depression in clinical settings, this link in community-dwelling individuals is ...inconclusive. The present study aimed at examining the association between serum 25(OH)D and PTH levels and the presence of depression in a national population-based household sample of 4,002 Jordanian participants aged ≥25 years. The DASS21 depression scale was used to screen for depression, and serum concentrations of 25(OH)D and PTH were measured by radioimmunoassay. Multiple logistic regression models were used to explore the association between serum 25(OH)D and PTH levels and depression. The unadjusted odds ratio (OR) decreased linearly with increasing quartiles of serum 25(OH)D (
P
trend
= 0.00). The OR for having depression was significantly higher among individuals in the first and second quartiles (OR = 1.4, 1.23, respectively) than among those in the fourth quartile (
P
values = 0.00 and 0.03, respectively). This relationship remained significant after adjusting for age, sex, marital status, education, BMI, serum creatinine, number of chronic diseases (OR = 1.39 and 1.21 and
P
values = 0.00 and 0.05, respectively) and after further adjustment for exercise, altitude, and smoking (OR = 1.48 and 1.24, respectively, and
P
values = 0.00 and 0.03, respectively). No significant association was found between serum PTH levels and depression. The decrease in risk of depression among participants started to be significant with serum 25(OH) D levels higher than 42.3 ng/ml (lower limit of the range of the third quartile). This value may help pinpoint the desirable level of serum 25(OH)D to be attained to help aid the prevention and treatment of depression.
Context. The formation and evolution of gas and dust environments around Be supergiants are still open issues. Aims. We intend to study the geometry, kinematics and physical structure of the ...circumstellar environment (CE) of the Be supergiant CPD−52 9243 to provide further insights into the underlying mechanism causing the Be phenomenon. Methods. The influence of the different physical mechanisms acting on the CE (radiation pressure, rotation, bi-stability or tidal forces) is somehow reflected in the shape and kinematic properties of the gas and dust regions (flaring, Keplerian, accretion or outflowing disks). To investigate these processes we mainly used quasi-simultaneous observations taken with high spatial resolution optical long-baseline interferometry (VLTI/MIDI), near-IR spectroscopy of CO bandhead features (Gemini/Phoenix and VLT/CRIRES) and optical spectra (CASLEO/REOSC). Results. High angular resolution interferometric measurements obtained with VLTI/MIDI provide strong support for the presence of a dusty disk(ring)-like structure around CPD−52 9243, with an upper limit for its inner edge of ~8 mas (~27.5 AU, considering a distance of 3.44 kpc to the star). The disk has an inclination angle with respect to the line of sight of 46 ± 7°. The study of CO first overtone bandhead evidences a disk structure in Keplerian rotation. The optical spectrum indicates a rapid outflow in the polar direction. Conclusions. The IR emission (CO and warm dust) indicates Keplerian rotation in a circumstellar disk while the optical line transitions of various species are consistent with a polar wind. Both structures appear simultaneously and provide further evidence for the proposed paradigms of the mass-loss in supergiant Be stars. The presence of a detached cold CO ring around CPD–52 9243 could be due to a truncation of the inner disk caused by a companion, located possibly interior to the disk rim, clearing the center of the system. More spectroscopic and interferometric data are necessary to determine a possible binary nature of the star.
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