bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metallicity Dependences of Massive Star Formation from Theoretical and Observational Perspectives
Authors: Tanaka K. E. I. , Zhang Y. , Shimonishi T. , Matsukoba R. 
Published: August 2024

AbstractMassive stars play crucial roles in astrophysical settings across cosmic history, and thus it is a fundamental problem to understand whether their formation processes are universal or diverse in various galactic environments. In particular, metallicity is the essential characteristic of cosmic evolution. Our theoretical studies have suggested some degrees of metallicity dependence of massive star formation. In the extremely metal-poor case of , protostellar disks are significantly unstable, and the photoionization feedback is more efficient. We also execute an ALMA survey targeting massive protostars in the Large Magellanic Clouds (LMC) with . We found that the outflow properties of LMC protostars (mass, momentum, energy) are consistent with those of Galactic protostars, suggesting the universality of massive star formation at least in the range of .
Can we detect deep axisymmetric toroidal magnetic fields in stars?
Authors: Dhouib Hachem , Mathis Stéphane , Bugnet Lisa , Van Reeth Timothy , Aerts Conny 
Published: August 2024

AbstractThe current angular momentum (AM) transport models fail to reproduce asterosieimic observations. One of the best candidates to explain this discrepancy is the magnetic field in radiative zones with its various possible topologies, for instance axisymmetric toroidal magnetic field. If such azimuthal field is strong enough, the Tayler’s instability could occur which induces a magnetic torque that allows a very efficient transport of AM and could trigger dynamo action in radiative layers. If such important field does not emerge at the surface, spectropolarimetry is blind. In this case, the only way to detect and characterise the field is by using magneto-asteroseismology. It consists in searching for the characteristic signatures of magnetic field in the observed frequency spectra of stellar oscillations.
Apparently isolated massive stars within Galactic Hii regions
Authors: de la Fuente Diego , Marco Amparo , Negueruela Ignacio , Patrick Lee R. , Herrero Artemio , Eikenberry Stephen S. 
Published: August 2024

AbstractThe Alicante Survey of MAssive Stars in Hii Regions (A-SMASHeR) is aimed at finding the ratio of massive stars that are born in isolation. We present LIRIS/WHT images and EMIR/GTC spectra of the massive stellar content in A-SMASHeR regions. Our preliminary analysis yields ∼20% of regions hosting relatively (or truly) isolated massive stars.
Contact Tracing of Massive Binary Stars
Authors: Henneco Jan , Schneider Fabian R. N. , Hekker Saskia , Laplace Eva 
Published: August 2024

AbstractStellar mergers produce more massive, rejuvenated (strongly magnetic) stars, with potentially peculiar properties, and can be detected as luminous red novae. Using a grid of detailed 1D binary evolution models, we aim to determine which binary systems are likely to merge and at what evolutionary stage. This will tell us more about the merger products, and might help us understand some of the trends found in observed single- and multiple-star populations.
Massive stars and their large-separation low-mass companions in Sco OB1
Authors: Pauwels T. , Reggiani M. , Rainot A. , Sana H. 
Published: August 2024

AbstractExploring the low-mass end of the companion mass function around massive stars is of crucial importance to constrain massive star formation theories. We present a high-contrast imaging study of 20 O- and early B-type stars in the Scorpius OB1 association. From the analysis of VLT/SPHERE data, we identify a total of 789 sources. The data probe the brown dwarf regime around massive stars, resulting in the discovery of large-separation multiple systems with mass-ratios as low as 0.001 (comparable to Jupiter-Sun mass-ratio).
Introducing the ASSESS project: Episodic Mass Loss in Evolved Massive Stars - Key to Understanding the Explosive Early Universe
Authors: Bonanos A. Z. , Maravelias G. , Yang M. , Tramper F. , de Wit S. , Zapartas M. , Antoniadis K. , Christodoulou E. , Munoz-Sanchez G. 
Published: August 2024

AbstractEpisodic mass loss is not understood theoretically, neither accounted for in state-of-the-art models of stellar evolution, which has far-reaching consequences for many areas of astronomy. We introduce the ERC-funded ASSESS project (2018-2024), which aims to determine whether episodic mass loss is a dominant process in the evolution of the most massive stars, by conducting the first extensive, multi-wavelength survey of evolved massive stars in the nearby Universe. It hinges on the fact that mass-losing stars form dust and are bright in the mid-infrared. We aim to derive physical parameters of ∼1000 dusty, evolved massive stars in ∼25 nearby galaxies and estimate the amount of ejected mass, which will constrain evolutionary models, and quantify the duration and frequency of episodic mass loss as a function of metallicity. The approach involves applying machine-learning algorithms to select dusty, luminous targets from existing multi-band photometry of nearby galaxies. We present the first results of the project, including the machine-learning methodology for target selection and results from our spectroscopic observations so far. The emerging trend for the ubiquity of episodic mass loss, if confirmed, will be key to understanding the explosive early Universe and will have profound consequences for low-metallicity stars, reionization, and the chemical evolution of galaxies.
The impact of binary interaction on the main-sequence morphology of young star clusters
Authors: Wang Chen , Langer Norbert , Schootemeijer Abel , Milone Antonino , Hastings Ben , Xu Xiao-Tian , Bodensteiner Julia , Sana Hugues , Castro Norberto , Lennon D. J. , Marchant Pablo , de Koter A. , de Mink Selma E. 
Published: August 2024

AbstractSince massive stars form preferentially as members of close binary systems, we use dense grids of detailed binary evolution models to explore how binary evolution shapes the main-sequence morphology of young star clusters. We propose that binary mergers might be the origin of the blue main sequence stars in young star clusters. Our results imply that stars may either form by accretion, or through a binary merger, and that both paths lead to distinctly different spins, magnetic fields, and stellar mass distributions.
Numerical modeling of IR SEDs of dusty CCSN within a Bayesian framework
Authors: Zsíros Szanna , De Looze Ilse , Szalai Tamás 
Published: August 2024

AbstractWe investigate the physical properties of dust in the environment of three core-collapse supernovae (CCSNe) through mid-infrared (mid-IR) spectral energy distribution (SED) modeling (both analytical and numerical methods) and interpret our results within a Bayesian framework. We provide evidence that the observed late-time mid-IR excess of the SNe can be described by dust models. We conclude that in case of various types of SNe, numerical dust models with a shell-like geometry can be reconciled with analytical models, regarding the essential properties of dust grains.
Deciphering hard disks
Authors: Nazé Yaël , Rauw Gregor , Smith Myron A. , Motch Christian 
Published: August 2024

AbstractSome Be stars were found to emit very bright and extremely hard thermal X-rays. This so-called γ Cas -star category is rapidly growing, showing that the phenomenon is far from being uncommon and its consequences on Be population feedback should be examined. The origin of this X-ray peculiarity is however much debated. In this contribution, we review the most recent observational clues and derive constraints on the cause of the phenomenon: properties of these stars (multiplicity status, photometric variability), X-ray reaction to disk changes, impact of stripped-star companions on the X-ray emission,…
Nitrogen production in population III stars
Authors: Tsiatsiou S. , Georgy C. , Ekström S. , Meynet G. 
Published: August 2024

AbstractThe first stars in the Universe have inherited their composition from primordial nucleosynthesis, so they have no metal. These stars, which are also named population III (pop III) stars, began the process of reionization in the Universe and contributed to the metal enrichment with heavy elements. Previous studies showed that they should have been rotating fast due to small or no angular momentum loss, reaching easily the critical velocity since they are massive and have very low stellar winds, thus their mass loss is very low or zero. Our aim is to study how the production of primary nitrogen is affected due to high rotation in the pop III stars. So, we compared grids of pop III stars with zero, average, and high rotation. All these models have been computed using Geneva code (GENEC) in the mass range of 9M⊙≤Mini≤ 120M⊙. Due to the rotational mixing, the carbon produced in the He-burning core is diffused towards the H-burning shell, triggering the CNO cycle and producing primary nitrogen. In some models the transition of the shell from a pp-chain H-burning to a CNO H-burning induces a strong energy release and a complete change of the stellar structure and the nucleosynthesis. The production of nitrogen is boosted for the high rotation models.
Dependence of Wolf-Rayet wind clumping on the surface temperature
Authors: Chené André-Nicolas , St-Louis Nicole , Lenoir-Craig Guillaume , Moffat Anthony F. J. , Gayley Kenneth 
Published: August 2024

AbstractWe present our measurements of the amplitude of photometric and spectroscopic variability due to clumping in the wind of Wolf-Rayet (WR) stars. Photometric variability was assessed using TESS light-curves, while spectroscopic variations were obtained from almost 20 years of monitoring of nearly 100 classical (presumably single) stars. Our results show an apparent dependence of the variability amplitude with the stars’ surface temperature and/or terminal velocity. Our interpretation is that it supports the idea that the dominating driver of the clumps in WR winds is a sub-surface convection region.
A search for correlations between Wolf-Rayet stochastic wind variability and stellar parameters
Authors: Lenoir-Craig Guillaume , St-Louis Nicole , Moffat Anthony F. J. , Pablo Herbert 
Published: August 2024

AbstractWe present the results of our analysis of 122 light-curves from 50 Wolf-Rayet (WR) stars using a red+white noise analysis, where we compare the fitted red noise features with stellar parameters to assess the presence of correlations with stellar parameters. A significant correlation between the amplitude of variability α0 and v∞ was found for the whole sample, along with several other correlations satisfying the Spearman-Rank p<0.001 criterion for both He-burning and WNh stars. Our results are compatible with several plausible processes that can have an influence on the level of variability in the winds of these stars, including a subsurface convection zone and core-generated internal gravity waves.
The Nature of Unseen Companions in Massive Single-Line Spectroscopic Binaries
Authors: Sana Hugues , Abdul-Masih Michael , Banyard Gareth , Bodensteiner Julia , Bowman Dominic M. , Dsilva Karan , Eldridge C. , Fabry Matthias , Frost Abigail J. , Hawcroft Calum , Janssens Soetkin , Mahy Laurent , Marchant Pablo , Langer Norbert , Van Reeth Timothy , Sen Koushik , Shenar Tomer 
Published: August 2024

AbstractMassive stars are predominantly found in binaries and higher order multiples. While the period and eccentricity distributions of OB stars are now well established across different metallicity regimes, the determination of mass-ratios has been mostly limited to double-lined spectroscopic binaries. As a consequence, the mass-ratio distribution remains subject to significant uncertainties. Open questions include the shape and extent of the companion mass-function towards its low-mass end and the nature of undetected companions in single-lined spectroscopic binaries. In this contribution, we present the results of a large and systematic analysis of a sample of over 80 single-lined O-type spectroscopic binaries (SB1s) in the Milky Way and in the Large Magellanic Cloud (LMC). We report on the developed methodology, the constraints obtained on the nature of SB1 companions, the distribution of O star mass-ratios at LMC metallicity and the occurrence of quiescent OB+black hole binaries.
The evolution of binary-stripped stars: consequences for supernovae and black hole formation
Authors: Laplace Eva , Schneider Fabian , Podsiadlowski Philipp , de Mink Selma , Justham Stephen , Renzo Mathieu , Götberg Ylva , Farmer Rob , Vartanyan David 
Published: August 2024

AbstractGravitational-wave (GW) observations are revealing the population of compact objects from a new angle. Yet their stellar progenitors remain uncertain because few observational clues on their progenitors exist. Theoretical models typically assume that the progenitor evolution can be approximated with single-star models. We explore how binary evolution affects the pre-supernova (SN) structure of stars, and the resulting distribution of compact object remnants. We focus on the differences in the core properties of single stars and of donor stars that transfer their outer layers in binary systems and become binary-stripped. We show that the final structures of binary-stripped stars that lose their outer layers before the end of core helium burning are systematically different compared to single stars. As a result, we find that binary-stripped stars tend to explode more easily than single stars and preferentially produce neutron stars and fewer black holes, with consequences for GW progenitors.
Red Supergiants in M31: The Humphreys-Davidson limit at high metallicity
Authors: McDonald Sarah L. E. , Davies Ben , Beasor Emma R. 
Published: August 2024

AbstractThe empirical upper limit to Red Supergiant (RSG) luminosity, known as the Humphreys-Davidson (HD) limit, has been commonly explained as being caused by the stripping of stellar envelopes by metallicity-dependent, line-driven winds. As such, the theoretical expectation is that the HD limit should be higher at lower metallicity, where weaker mass-loss rates mean that higher initial masses are required for an envelope to be stripped. In this work, we test this prediction by measuring the luminosity function of RSGs in M31 and comparing to those in the LMC and SMC. We find that

$\[\log ({L_{{\rm{m}}ax}}/{L_ \odot }) = 5.53 \pm 0.03\]$

in M31 (Z ≳ Z⊙), consistent with the limit found for both the LMC (Z ∼ 0.5 Z⊙) and SMC (Z ∼ 0.25 Z⊙), while the RSG luminosity distributions in these 3 galaxies are consistent to within 1σ. We therefore find no evidence for a metallicity dependence on both the HD limit and the RSG luminosity function, and conclude that line-driven winds on the main sequence are not the cause of the HD limit.
The CubeSpec space mission: Asteroseismology of massive stars from time-series optical spectroscopy
Authors: Bowman D. M. , Vandenbussche B. , Sana H. , Tkachenko A. , Raskin G. , Delabie T. , Vandoren B. , Royer P. , Garcia S. , Van Reeth T. ,   the CubeSpec Collaboration
Published: August 2024

AbstractThe ESA/KU Leuven CubeSpec mission is specifically designed to provide low-cost space-based high-resolution optical spectroscopy. Here we highlight the science requirements and capabilities of CubeSpec. The primary science goal is to perform pulsation mode identification from spectroscopic line profile variability and empower asteroseismology of massive stars.
The Gaia view on massive stars: EDR3 and what to expect from DR3
Authors: Maíz Apellániz Jesús , Barbá Rodolfo H. , Pantaleoni González Michelangelo , Weiler Michael , Reed B. Cameron , Fernández Aranda Román , Crespo Bellido Pablo , Sota Alfredo , Alfaro Emilio J. , Molina Lera J. Alejo 
Published: August 2024

AbstractAt the time of this meeting, the latest Gaia data release is EDR3, published on 3 December 2020, but the next one, DR3, will appear soon, on 13 June 2022. This contribution describes, on the one hand, Gaia EDR3 results on massive stars and young stellar clusters, placing special emphasis on how a correct treatment of the astrometric and photometric calibration yields results that are simultaneously precise and accurate. On the other hand, it gives a brief description of the exciting results we can expect from Gaia DR3.
Ultraviolet observations of massive stars and the instrumentation to come
Authors: de Castro Ana I. Gómez 
Published: August 2024

AbstractThe wealth of information obtained about massive stars from observations at ultraviolet (UV) wavelengths has been fundamental to understand their structure and the mechanisms regulating their evolution. There are however, important aspects that have not yet been addressed due to the lack of data and the relevant instrumentation such as the role of binarity and magnetic fields or the impact of low metallicity in the evolution of massive stars. There are plans to develop UV spectropolarimeters, UV monitors and very efficient telescopes with high collecting surfaces that will revolutionize the field. In this contribution, a short update on the current and foreseen UV instrumentation is provided.
Stellar Atmospheres and Supernovae: Systematic Errors
Authors: John Hillier D. 
Published: August 2024

AbstractOver the last two decades there have been considerable advances in modelling the spectra of massive stars and supernovae (SNe). Despite this progress, there are still numerous uncertainties that affect the accuracy of models. For massive stars, convection, instabilities, clumping, and our inability to model stellar winds self-consistently likely introduce systematic errors into our analyses. For SNe, and particularly for core-collapse SNe, departures from spherical symmetry strongly affect observed spectra and need to be taken into account. There are also issues with clumping, and mixing processes (both in the progenitor and the SN explosion) that need to be resolved. For both massive stars and SNe, the accuracy and availability of atomic data continues to be an ongoing issue influencing analyses.
Observations south of HD 5980
Authors: Sixtos Andrés , Wofford Aida , Peimbert Antonio 
Published: August 2024

AbstractWe study the He II λ4686 emission south of multiple-star system HD 5980, which hosts two WN-type stars. We use optical VLT FORS1 long-slit spectra. The observations are close to the eclipse phase. Broad He II emission with a SNR >5 is observed as far as 7.6 pc from HD 5980. The He II emission that is closest to HD 5980 is 1.2 pc directly south and has a redshifted component with FWHM 1450 km s-1 originating in the eclipsing WN5-6 star, and a blueshifted component with FWHM 600 km s-1. The second component cannot be explained by either the nearly- eclipsed WN star or the nearby supernova remnant, SNR B0057-724. We suggest that the additional He II emission comes from the colliding winds of the two WN stars.
Deep‐Learning Analysis of Fracture Networks Leading to System‐Size Failure in Rocks
Authors: Mathiesen Joachim , McBeck Jessica , Cordonnier Benoît , Ben‐Zion Yehuda , Renard François 
Published: August 2024

AbstractFracture networks in rocks and other geomaterials form by seismic and aseismic damage processes that could lead to system‐size failure. Here, we use a multi‐view convolutional neural network model to predict the stress proximity to macroscopic failure of experimentally deformed rock samples using two‐dimensional images. Models are trained on time series of fractures observed in rock samples through dynamic in situ synchrotron X‐ray tomography experiments. The results demonstrate that deep learning models outperform traditional estimates based on fracture density, increasing the accuracy of the predictions. Furthermore, the models provide insights into fundamental characteristics of fracture patterns that may provide precursory information on impending material failure. The trained deep learning models estimate the angle of the fracture plane relative to the principal loading direction, which is a key factor contributing to shear failure. The predicted angle of the fracture plane, in the range of 10°–30° with respect to the direction of maximum compressive stress, is consistent with the established failure criteria used in rock mechanics.
Misaligned Wind‐Waves Behind Atmospheric Cold Fronts
Authors: Sauvage César , Seo Hyodae , Barr Benjamin W. , Edson James B. , Clayson Carol Anne 
Published: August 2024

AbstractAtmospheric fronts embedded in extratropical cyclones are high‐impact weather phenomena, contributing significantly to mid‐latitude winter precipitation. The three vital characteristics of the atmospheric fronts, high wind speeds, abrupt change in wind direction, and rapid translation, force the induced surface waves to be misaligned with winds exclusively behind the cold fronts. The effects of the misaligned waves under atmospheric cold fronts on air‐sea fluxes remain undocumented. Using the multi‐year in situ near‐surface observations and direct covariance flux measurements from the Pioneer Array off the coast of New England, we find that the majority of the passing cold fronts generate misaligned waves behind the cold front. Once generated, the waves remain misaligned, on average, for about 8 hr. The parameterized effect of misaligned waves in a fully coupled model significantly increases the roughness length (185%), drag coefficient (19%), and air‐sea momentum flux (11%). The increased surface drag reduces the wind speeds in the surface layer. The upward turbulent heat flux is weakly decreased by the misaligned waves because of the decrease in temperature and humidity scaling parameters being greater than the increase in friction velocity. The misaligned wave effect is not accurately represented in a commonly used wave‐based bulk flux algorithm. Yet, considering this effect in the current formulation improves the overall accuracy of parameterized momentum flux estimates. The results imply that better representing a directional wind‐wave coupling in the bulk formula of the numerical models may help improve the air‐sea interaction simulations under the passing atmospheric fronts in the mid‐latitudes.
Improved Precipitation Diurnal Cycle in GFDL Climate Models With Non‐Equilibrium Convection
Authors: Zhang Bosong , Donner Leo J. , Zhao Ming , Tan Zhihong 
Published: August 2024

AbstractMost global climate models with convective parameterization have trouble in simulating the observed diurnal cycle of convection. Maximum precipitation usually happens too early during summertime, especially over land. Observational analyses indicate that deep convection over land cannot keep pace with rapid variations in convective available potential energy, which is largely controlled by boundary‐layer forcing. In this study, a new convective closure in which shallow and deep convection interact strongly, out of equilibrium, is implemented in atmosphere‐only and ocean‐atmosphere coupled models. The diurnal cycles of convection in both simulations are significantly improved with small changes to their mean states. The new closure shifts maximum precipitation over land later by about three hours. Compared to satellite observations, the diurnal phase biases are reduced by half. Shallow convection to some extent equilibrates rapid changes in the boundary layer at subdiurnal time scales. Relaxed quasi‐equilibrium for convective available potential energy holds in significant measure as a result. Future model improvement will focus on the remaining biases in the diurnal cycle, which may be further reduced by including stochastic entrainment and cold pools.