Context
. Without a doubt, mass transfer in close binary systems contributes to the populations ofWolf-Rayet (WR) stars in the MilkyWay and the Magellanic Clouds. However, the binary formation ...channel is so far not well explored.
Aims
. We want to remedy this by exploring large grids of detailed binary and single star evolution models computed with the publicly available MESA code, for a metallicity appropriate for the Large Magellanic Cloud (LMC).
Methods
. The binary models were calculated through Roche-lobe overflow and mass transfer, until the initially more massive star exhausted helium in its core. We distinguish models of WR and helium stars based on the estimated stellar wind optical depth. We used these models to build a synthetic WR population, assuming constant star formation.
Results
. Our models can reproduce the WR population of the LMC to significant detail, including the number and luminosity functions of the main WR subtypes. We find that for binary fractions of 100% (50%), all LMC WR stars below 10
6
L
⊙
(10
5.7
L
⊙
) are stripped binary mass donors. We also identify several insightful mismatches. With a single star fraction of 50%, our models produce too many yellow supergiants, calling either for a larger initial binary fraction, or for enhanced mass loss near the Humphreys-Davidson limit. Our models predict more long-period WR binaries than observed, arguably due to an observational bias toward short periods. Our models also underpredict the shortest-period WR binaries, which may have implications for understanding the progenitors of double black hole mergers.
Conclusions
. The fraction of binary-produced WR stars may be larger than often assumed and outline the risk to miscalibrate stellar physics when only single star models are used to reproduce the observed WR stars.
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The objective of this study was to investigate human leucocyte antigen (HLA) genes in patients chronically infected with hepatitis C virus (HCV) and to analyse the possible role of these genes in the ...progression of chronic hepatitis C. One hundred and forty‐five (145) Brazilian patients infected only with HCV genotype 1 were evaluated. HLA class I (A*, B*, C*) and class II (DRB1*, DQA1*, DQB1*) typing were carried out by PCR‐SSO, through Luminex technology. Associations were found with protection against development of liver damage by both DRB1*11 (5.0% versus 18.2%, P = 0.0016, OR = 0.23, CI 95% = 0.09–0.58; Pc=0.0208) and DRB1*11‐DQA1*05‐DQB1*03 haplotype (4.2% versus 15.3%, P = 0.0032; OR = 0.24, CI 95% = 0.08‐0.64). Liver damage was associated with HLA‐C*04 in patients with <20 years of infection (38.4% versus 9.1%, P = 0.002, OR = 6.25, CI 95% = 1.97–19.7; Pc=0.0238). It is concluded that HLA alleles can influence the development of liver damage in HCV type‐1 chronically infected Brazilian patients.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Recently, astrometric and spectroscopic surveys of OB stars revealed a few stellar-mass black holes (BHs) with orbital periods of as low as 10 days. Contrary to wind-fed BH high-mass X-ray binaries ...(HMXBs), no X-ray counterpart was detected, probably because of the absence of a radiatively efficient accretion disc around the BH. Nevertheless, dissipative processes in the hot, dilute, and strongly magnetised plasma around the BH (so-called BH corona) can still lead to non-thermal X-ray emission (e.g. synchrotron). We determine the X-ray luminosity distribution from BH+OB star binaries up to orbital periods of a few thousand days. odot $ and orbital periods of 1-3000\,d. We computed the X-ray luminosity for a broad range of radiative efficiencies that depend on the mass accretion rate and flow geometry. odot $, which aligns well with our predictions and may be interesting sources for follow-up observations. The predicted luminosities of the OB companions to these X-ray-emitting BHs are 10$^ odot These findings advocate for prolonged X-ray observations of the stellar-mass black hole candidates identified in the vicinity of OB stars. Such long exposures could reveal the underlying population of X-ray-faint BHs and provide constraints for the evolution from single to double degenerate binaries and identify the progenitors of gravitational wave mergers.
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Massive star feedback affects the evolution of galaxies, where the most massive stars may have the largest impact. The majority of massive stars are born as members of close binary systems. In this ...work, we investigated detailed evolutionary models of very massive binaries (30−90
M
⊙
) with Large Magellanic Cloud (LMC) metallicity. We identify four effects defying the conventional knowledge of binary evolution, which are all related to the proximity of the models to the Eddington limit. We find that the majority of systems undergo mass transfer during core hydrogen burning. During the ensuing nuclear timescale evolution, many mass donors remain more massive than their companions (‘reverse Algols’), and nuclear timescale mass transfer may be interrupted or absent altogether. Furthermore, due to the elevated luminosity-to-mass ratio, many of the core-hydrogen-burning donors may develop Wolf-Rayet-type winds at luminosities where single stars would not. We identify observational counterparts of very massive reverse Algol binaries in the LMC and discuss their contribution to the observed hydrogen-rich Wolf-Rayet stars. We argue that understanding very massive Algol systems is key to predicting the advanced evolution of very massive binaries, including their ability to evolve into observable gravitational wave sources.
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Transmission is a central feature of pathogen fitness and influences host population dynamics. The form and magnitude of transmission rates determine whether a pathogen establishes itself in a host ...population and the proportion of a population that becomes infected. While the effects of environmental variation on pathogen transmission dynamics have received substantial attention, the time and number of pathogen exposure in relation to host ontogeny has been relatively less investigated. Such understanding is particularly important in host species exhibiting distinct life‐history stages such as amphibians as this temporal variation in infection modulates transmission trends at the population level. We investigated the role of the timing and number of ranavirus (FV3) exposures on infection rate and mortality patterns in Lithobates pipiens tadpoles in a two‐step laboratory experiment with four treatments: individuals exposed as hatchlings but not as tadpoles, individuals not exposed as hatchlings but exposed as tadpoles, individuals exposed both as hatchlings and tadpoles and individuals that were never exposed. Our results indicate that individuals exposed twice presented higher infection and mortality rates over individuals exposed only once (infection: 40 vs. 16%; mortality: 16.8 vs. 8.1%, respectively). Among individuals exposed only once, but at different time, no difference in mortality was observed; yet, dissimilar infection rates indicate a differential capacity to carry and transmit virions among various developmental stages suggesting distinct epidemiological roles. Our results stress the importance of considering stage‐dependent host susceptibility to better understand infection patterns and transmission dynamics and advocate its incorporation in models and field study designs.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Objectives Aim of the study was assessing motivation to change in a clinical sample of adolescents with anorexia nervosa and its relation to specific cognitions and behaviours. Methods N= 77 patients ...with anorexia nervosa (75 female, 2 males, mean age = 15.8, SD = 1.3) were evaluated with Anorexia Nervosa Stage of Change Questionnaire (ANSOCQ) measuring motivation to recover and further questionnaires evaluating treatment and course of the disorder. The latter included Eating Disorder Inventory (EDI-2), the Eating Attitude Test (EAT), the Pros and Cons of Anorexia nervosa questionnaire (PCAN), and the Body Image Questionnaire (FKAN). Data were collected at treatment onset (T1), follow-up was after 12 months (T2). Results At T1 motivation to change was significantly related to the EDI subscale measuring drive for thinness (p < .001) and body dissatisfaction (p< .01), to the PCAN pros scales measuring appearance (p< .01) and safe/structure (p< .01), to the EAT scale measuring dieting (p< .001) and the FKAN subscale measuring the feeling of body massivity (p< .001).The stage of motivation to change at treatment onset was very low in the sample (67% in stage 1 = precontemplation or 2 = contemplation). There was no relation between motivation at T1 and BMI at T2 but the increase of motivation between T1 and T2 predicted a better outcome (BMI at T2). Conclusions Motivation to change is related to specific cognitions and behaviours in adolescent patients with anorexia nervosa. Increase of treatment motivation during the first months of treatment seems to be predictive for outcome.
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GEOZS, IMTLJ, KILJ, NUK, OILJ, PNG, SBCE, SBJE, UL, UM, UPUK
Objectives The aim of the study was assessing differences in selected psychosocial and behavioural variables between a referred sample of patients with an eating disorder, a non-referred risk sample ...with eating problems, and a healthy control group. Methods There were N=100 patients (95 females and 5 males, Mean age = 15.8, SD = 1.3) in the referred sample. The two matched non-referred groups of each N=215 participants (95% females, 5% males; Mean age =16.1, SD = 1.5) stem from the Zurich Adolescent Psychology- and Psychopathology-Study (ZAPPS). Emotional and behavioural problems were assessed using the Youth Self Report (YSR) and a depression scale. In addition, the participants responded to questionnaires covering life events, self-related cognitions, coping capacities, perceived parental behaviour, and family climate. Results Compared to both non-referred groups, the referred sample had significantly higher scores on the social withdrawn, anxious/depressed and thought problems scale of the YSR, on the depression and the life events scales, and significantly lower scores on the self esteem scale. Compared to the referred sample, the non-referred risk sample had significantly higher scores on the YSR-scale measuring externalizing problems and the perceived parental rejection scale, but lower scores on the family climate scales measuring cohesion and adaptability. Conclusions The three groups were differentiated by various psychosocial and behavioural variables. Externalizing problems and indicators of a poor family climate were more common in a non-referred high-risk group with eating problems than in a referred sample with clinical eating disorders.
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GEOZS, IMTLJ, KILJ, NUK, OILJ, PNG, SBCE, SBJE, UL, UM, UPUK
Background: There are conflicting reports regarding the effects of atrazine (ATZ) on amphibian development. Therefore, further studies are needed to examine the potential mechanisms of action of ATZ ...in amphibians. Objectives: Our aim in this study was to determine whether low concentrations of ATZ affect gonadal development and metamorphosis in the Northern leopard frog, Rana pipiens. Methods: Tadpoles were exposed in outdoor mesocosms to nominal concentrations of 0.1 and 1.8 μg/L of formulated ATZ from Gosner stage 27 (G27) to metamorphic climax (G42). Exposure to 17α-ethinylestradiol (EE₂; 1.5 μg/L) provided a positive control for induction of testicular oocytes in males. Endocrine-related gene expression and gonadal histopathology were examined at G42 and in a subset of premetamorphic G34 tadpoles that failed to metamorphose. Results: Gonadal gross morphology revealed that the 1.8-μg/L ATZ treatment produced 20% more females compared with the control. Histologic analysis revealed that 22% of EE₂-treated males had testicular oocytes, whereas none were observed in any animals from the control or either ATZ groups. ATZ increased brain estrogen receptor α mRNA to 2.5 times that of the control at premetamorphosis and altered liver levels of 5β-reductase activity at metamorphosis. In contrast, brain aromatase mRNA level and activity did not change. ATZ treatments significantly reduced metamorphic success (number of animals reaching metamorphosis) without affecting body weight, snout—vent length, or age at metamorphosis. Gene expression analysis indicated that ATZ decreased the expression of deiodinase type 3 in the tail at premetamorphosis. Conclusions: Our study indicates that exposure to low concentrations of ATZ in experimental mesocosms alters gonadal differentiation and metamorphosis in developing R. pipiens.
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BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Standard binary evolutionary models predict a significant population of core helium-burning stars that lost their hydrogen-rich envelope after mass transfer via Roche-lobe overflow. However, there is ...a scarcity of observations of such stripped stars in the intermediate-mass regime (∼1.5 − 8
M
⊙
), which are thought to be prominent progenitors of SN Ib/c. Especially at low metallicity, a significant fraction of these stars are expected to be only partially stripped, retaining a significant amount of hydrogen on their surfaces. For the first time, we discovered a partially stripped massive star in a binary with a Be-type companion located in the Small Magellanic Cloud (SMC) using a detailed spectroscopic analysis. The stripped-star nature of the primary is revealed by the extreme CNO abundance pattern and very high luminosity-to-mass ratio, which suggest that the primary is likely shell-hydrogen burning. Our target SMCSGS-FS 69 is the most luminous and most massive system among the known stripped star + Be binaries, with
M
stripped
∼ 3
M
⊙
and
M
Be
∼ 17
M
⊙
. Binary evolutionary tracks suggest an initial mass of
M
ini
≳ 12
M
⊙
for the stripped star and predict it to be in a transition phase towards a hot compact He star, which will eventually produce a stripped-envelope supernova. Our target marks the first representative of an as-yet-missing evolutionary stage in the formation pathway of Be X-ray binaries and double neutron star mergers.
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Massive stars rotate faster, on average, than lower mass stars. Stellar rotation triggers hydrodynamical instabilities which transport angular momentum and chemical species from the core to the ...surface. Models of high-mass stars that include these processes predict that chemical mixing is stronger at lower metallicity. We aim to test this prediction by comparing the surface abundances of massive stars at different metallicities. We performed a spectroscopic analysis of single O stars in the Magellanic Clouds (MCs) based on the ULLYSES and XshootU surveys. We determined the fundamental parameters and helium, carbon, nitrogen, and oxygen surface abundances of 17 LMC and 17 SMC non-supergiant O6-9.5 stars. We complemented these determinations by literature results for additional MCs and also Galactic stars to increase the sample size and metallicity coverage. We investigated the differences in the surface chemical enrichment at different metallicities and compared them with predictions of three sets of evolutionary models. Surface abundances are consistent with CNO-cycle nucleosynthesis. The maximum surface nitrogen enrichment is stronger in MC stars than in Galactic stars. Nitrogen enrichment is also observed in stars with higher surface gravities in the SMC than in the Galaxy. This trend is predicted by models that incorporate chemical transport caused by stellar rotation. The distributions of projected rotational velocities in our samples are likely biased towards slow rotators. A metallicity dependence of surface abundances is demonstrated. The analysis of larger samples with an unbiased distribution of projected rotational velocities is required to better constrain the treatment of chemical mixing and angular momentum transport in massive single and binary stars.
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