bluuebunny/crossref_metadata_2025_split huggingface dataset:
Very Massive Stars: Near and Far
Authors: Martinet Sébastien , Meynet Georges , Ekström Sylvia , Georgy Cyril , Haemmerlé Lionel , Nandal Devesh , Hirschi Raphael 
Published: August 2024

AbstractIn addition to being spectacular objects, very massive stars (VMS) are suspected to have a tremendous impact on their environment and on the whole cosmic evolution. The nucleosynthesis both during their advanced stages and their final explosion likely contribute greatly to the overall enrichment of the Universe. Their resulting Supernovae are candidates for the most superluminous events and their extreme conditions lead also to very important radiative and mechanical feedback effects, from local to cosmic scale. With the recent implementation of a new equation of state in the GENEC stellar evolution code, appropriate for describing the conditions in the central regions of very massive stars in the advanced phases, we present new results on VMS evolution from Population III to solar metallicity. We explore their evolution and final fate as potential (P)PISNe across the cosmic time. We compare our results to recent spectroscopic observations of VMS in the Large Magellanic Cloud (LMC). We also underline the important radiative feedback of Population III VMS during the reionization epoch and the chemical contribution of these stars at high metallicity, especially for short-lived radionuclei.
MUSE 3D spectroscopy of BA-type supergiants in NGC 300
Authors: González-Torà Gemma , Urbaneja Miguel A. , Przybilla Norbert , Dreizler Stefan , Roth Martin M. , Kamann Sebastian , Castro Norberto 
Published: August 2024

AbstractWe present the results obtained using spectroscopic data taken with the intermediate-resolution Multi Unit Spectroscopic Explorer (MUSE) of B and A-type supergiants and bright giants in the Sculptor Group galaxy NGC 300. For our analysis, a hybrid local thermodynamic equilibrium (LTE) line-blanketing+non-LTE method was used to improve the previously published results for the same data. In addition, we present some further applications of this work, which includes extending the flux-weighted gravity luminosity relationship (FGLR), a distance determination method for supergiants. This pioneering work opens up a new window to explore this relation, and also demonstrates the enormous potential of integral field spectroscopy (IFS) for extragalactic quantitative stellar studies.
Plaskett’s Star: a fundamental revision of the architecture of the system
Authors: Stacey E. , Wade G. A. , Grunhut J. H. , Folsom C. P. , Kochukhov O. 
Published: August 2024

AbstractA century of study has characterized Plaskett’s Star (HD 47129) as an evolved, massive, short-period, equal mass O+O binary system. The discovery of a magnetic field in the broad-line component by Grunhut et al. (2013) renewed interest in the study of this system and led to its establishment as the most rapidly rotating magnetic O-type star. Grunhut et al. (2021) observed the circular polarization signatures of the magnetic star to exhibit no radial velocity variations while the narrow-line star demonstrates radial velocity variations consistent with the established orbital period. This has raised fundamental questions about the architecture of this system and the nature of the magnetic star which have led to a major shift in our understanding of HD 47129.
MAGIC Intensity Interferometer as a powerful tool to understand massive stars
Authors: Jiménez Martínez Irene , Acciari V. A. , Colombo E. , Cortina J. , Delgado C. , Díaz C. , Fink D. , Fiori M. , Guberman D. , Hassan T. , Lyard E. , Mangano S. , Mariotti M. , Martínez G. , Mirzoyan R. , Naletto G. , Njoh Ekoume T. , Produit N. , Polo M. , Rodríguez J. J. , Schweizer T. , Walter R. , Wunderlich C. , Zampieri L. ,   for the MAGIC collaboration
Published: August 2024

AbstractThe Intensity Interferometry technique consists of measuring the spatial coherence (visibility) of an object via its intensity fluctuations over a sufficient range of telescope separations (baselines). This allows us to study the size, shape and morphology of stars with an unprecedented resolution. Cherenkov telescopes have a set of characteristics that coincidentally allow for Intensity Interferometry observations: very large reflective surfaces, sensitivity to individual photons, temporal resolution of nanoseconds and the fact that they come in groups of several telescopes. In the recent years, the MAGIC Collaboration has developed a deadtime-free Intensity Interferometry setup for its two 17 m diameter Cherenkov telescopes that includes a 4-channel GPU-based real-time correlator, 410–430 nm filters and new ways of splitting its primary mirrors into submirrors using Active Mirror Control (AMC). With this setup, MAGIC can operate as a long-baseline optical interferometer in the baseline range 40–90 m, which translates into angular resolutions of 0.5-1 mas. Additionally, thanks to its AMC, it can simultaneously measure the zero-baseline correlation or, by splitting into submirrors, access shorter baselines under 17 m in multiple u-v plane orientations. The best candidates to observe with this technique are relatively small and bright stars, in other words, massive stars (O, B and A types). We will present the science cases that are currently being proposed for this setup, as well as the prospects for the future of the system and technique, like the possibility of large-scale implementation with CTA.
Apsidal Motion in Massive Binaries: CPD-41° 7742, an Extreme Case?
Authors: Rosu S. , Rauw G. , Nazé Y. , Gosset E. , Sterken C. 
Published: August 2024

AbstractWe study the apsidal motion in close eccentric massive binaries. Measuring the rate of apsidal motion in such a system gives insight into the internal structure and evolutionary state of the stars. We focus on CPD-41° 7742, for which independent studies in the past showed large discrepancies in the longitude of periastron of the orbit, hinting at the presence of apsidal motion. We perform a consistent analysis of all observational data to solve this apparent discrepancy and report the first determination of apsidal motion in this system. This study confirms the need for enhanced mixing in the stellar evolution models of the primary star to reproduce the observational properties. This points towards larger convective cores than usually considered.
Metal-poor Wolf-Rayet star enriching the ISM by nitrogen in the galaxy NGC 4068
Authors: Yarovova Anastasiya , Egorov Oleg , Moiseev Alexei , Maryeva Olga 
Published: August 2024

AbstractWe discovered a nebula in the low-metallicity (Z=0.1 ) nearby ( Mpc) dwarf galaxy NGC 4068, which reveals broad Hα line profile and unusual emission line fluxes in its spectrum. The object also shows significant nitrogen overabundance, not typical for metal-poor environment. We assumed that the nebula could be ionized by an evolved massive star with , Wolf-Rayet or Blue Supergiant, and built models of the nebula using Cloudy and CMFGEN codes. Our models successfully reproduce the optical emission spectrum of the object, including the peculiar [SII]/[NII] ratio and the presence of the HeII λ4686 line.
PION: Simulating bow shocks and circumstellar nebulae around massive stars
Authors: Mackey Jonathan , Green Samuel , Moutzouri Maria , Haworth Thomas J. , Kavanagh Robert D. , Celeste Maggie , Brose Robert , Zargaryan Davit 
Published: August 2024

AbstractExpanding nebulae are produced by mass loss from stars, especially during late stages of evolution. We describe the algorithms and methods implemented in the radiation-magnetohydrodynamics (MHD) code PION for highly scalable simulations using static mesh-refinement. We present results from 3D MHD simulations of bow shocks around runaway massive stars, and of the expansion of a fast wind from a Wolf-Rayet star into the slow wind from a previous red supergiant phase of evolution. PION is free software that can be downloaded from https://www.pion.ie/
Revisiting the Cygnus OB associations
Authors: Quintana Alexis L. , Wright Nicholas J. 
Published: August 2024

AbstractWe have studied the validity of the historical Cygnus OB associations and have found that many do not show the kinematic coherence expected for true OB associations. We have revisited these groups by photometrically identifying thousands of OB stars across the region with an SED fitting process which combines photometry, astrometry, spectral and evolutionary models. We applied a flexible clustering method and identified seven kinematically-coherent new OB associations. We observe a distinct correlation between position and velocity for two sets of these associations that suggests an expansion pattern. Tracing the motion of the stars back in the past we find that the sets were at their closest around 7.9 and 8.5 Myr ago. We discuss whether this expansion is a natural by-product of the commonly observed size - velocity dispersion relation of molecular clouds, or requires feedback to initiate the dispersal.
In-Situ Field Massive Star Formation in the Small Magellanic Cloud
Authors: Vargas-Salazar I. , Oey M. S. , Barnes J. R. , Chen X. , Castro N. , Kratter K. M. , Faerber T. A. 
Published: August 2024

AbstractA fundamental question for theories of massive star formation is whether OB stars can form in isolation. We assess the contribution of any in-situ OB star formation by using 210 field OB stars in the Small Magellanic Cloud (SMC) from the Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4). We search for tiny, sparse clusters around our target OB stars using cluster-finding algorithms. Employing statistical tests, we compare these observations with random-field data sets. We find that ∼5% of our target fields do show evidence of higher central stellar densities, implying the presence of small clusters. This frequency of small clusters is low and within errors, it is also consistent with the field OB population being composed entirely of runaway and walkaway stars. Assuming this small cluster fraction is real, it implies that some OB stars may form in highly isolated conditions. The low frequency could be caused by these clusters evaporating on a short timescale. However, another interpretation is that the low fraction of small clusters is observed because these form rarely, or not at all, implying a higher cluster lower-mass limit and generally consistent with a relationship between maximum stellar mass (mmax) and the cluster mass (Mcl).
Open questions in massive star research
Authors: Langer N. 
Published: August 2024

AbstractIn discussing open question in the field of massive stars, I consider their evolution from birth to death. After touching upon massive star formation, which may be bi-modal and not lead to a zero-age main sequence at the highest masses, I consider the consequences of massive stars being close to their Eddington limit. Then, when discussing the effects of a binary companion, I highlight the importance of massive Algols and contact binaries for understanding the consequences of mass transfer, and the role of binaries in forming Wolf-Rayet stars. Finally, a discussion on pair instability supernovae and of superluminous supernovae is provided.
ASSESSing evolved massive stars in NGC 6822 and IC 10
Authors: Munoz-Sanchez G. , Maravelias G. , Bonanos A. Z. , Tramper F. , de Wit S. , Yang M. 
Published: August 2024

AbstractThe role of mass loss from massive stars, especially episodic mass loss, is one of the outstanding open questions facing stellar evolution theory. Multiple lines of evidence are pointing to violent, episodic mass-loss events being responsible for removing a large part of the massive stellar envelope, especially in low-metallicity galaxies. The ERC ASSESS project 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. The project hinges on the fact that mass-losing stars form dust and are bright in the mid-infrared. We aim to investigate the properties of evolved targets in nearby galaxies and estimate the amount of ejected mass, which will constrain evolutionary models. In this work we present some of our first observational results from the galaxies NGC 6822 and IC 10 obtained with OSIRIS (GTC).
A SITELLE view of the Galactic Wolf-Rayet Nebulae NGC6888 and NGC2359
Authors: St-Louis N. , Dumontier C. , Ruest M. , Drissen L. 
Published: August 2024

AbstractIn this paper, we present a glimpse of our observations of two Wolf-Rayet (WR) nebulae, NGC2359 and NGC6888 obtained with the SITELLE imaging Fourier transform spectrograph. The data are of unprecedented spatial coverage and cover a broad wavelength range.
X-raying massive stars and their feedback near and far
Authors: Oskinova Lidia 
Published: August 2024

AbstractMassive stars emit X-rays. Despite modest X-ray luminosities of single hot massive stars, the ongoing large observing campaigns combining X-ray and UV spectroscopy provide a tomographic view of stellar winds. It is now established that X-ray radiation is modulated with stellar rotation and shows the same period as discrete absorption components (DACs) in the UV resonance lines. The latter are associated with corotating interaction regions (CIRs) in stellar winds, therefore the mechanisms responsible for generation of X-rays and CIRs appear to be physically linked. Binary massive stars with accreting compact companions – high-mass X-ray binaries (HMXBs) – are routinely observed by modern X-ray observatories at Mpc distances. Joint observations in X-ray and UV allow to determine realistic properties of these systems. The brightest sources among HMXBs are ultraluminous X-ray sources (ULXs). Their powerful radiation is an important source of stellar feedback. HMXBs are the products of massive binary evolution and are typically found in the vicinity of young massive star clusters. The superstar clusters blow hot superbubbles which fill large areas in star-forming dwarf galaxies. Recent models show that X-ray emission from superbubbles is likely the dominant source of He ii ionization in metal-poor star-forming dwarf galaxies. To conclude, X-ray observations provide an important window for studying massive stars and their feedback near and far.
Clumping and X-rays in cool B-Supergiants
Authors: Bernini-Peron Matheus , Marcolino W. L. F. , Sander A. A. C. 
Published: August 2024

AbstractB supergiants (BSGs) lie on the cool end of line-driven wind regime, such that the study of their atmospheres can help us to understand the physics of line-driven winds. So far key features of their spectra, especially in the UV region, could not be reproduced consistently with atmosphere models. This represents a significant gap in our knowledge of their physical properties and behavior, which is particularly striking for BSGs on the cool side of the Bi-Stability Jump (cooler than B1). To address this problem, we analysed a sample of Galactic cool BSGs, with sufficient UV and optical coverage. None of our targets are detected in X-rays with only upper limits existing for some of them.
Rapid Identification of Greigite in Lacustrine Sediments Using SIRM/χ and χARM: Insights From the Cuo E Core, Tibetan Plateau, China
Authors: Ding Shengchang , Dekkers Mark J. , Li Mingkun , Zhao Qi , Yan Yi , Zhu Zhaoyu 
Published: August 2024

AbstractThe Cuo E (CE) core contains the entire Quaternary stratigraphy of the CE Lake (31°24′–31°.32′ N, 91°28′–91°33′E, Tibetan Plateau, China). Here, we study the magnetic properties of 1,748 samples from the CE core, combined with scanning electron microscopy and X‐ray energy dispersive spectrometer analysis on selected samples. The main magnetic minerals appear to be magnetite and greigite. To further quantify the presence of greigite in CE core, 84 samples were analyzed using rock magnetism in more detail including: susceptibility (χ) versus temperature, coercivity component analysis of acquisition curves of the isothermal remanent magnetization (IRM), and principal component analysis of the first‐order reversal curve (FORC) diagrams. The greigite content and saturation IRM over susceptibility (SIRM/χ) appear to be exponentially related. SIRM/χ can be used as greigite concentration indicator. We also propose a rapid way to identify greigite in the CE core: When SIRM/χ increases and anhysteretic remanent susceptibility (χARM) increases only slowly, the sample contains greigite. Samples with SIRM/χ < 15 kA/m also follow this relation. This greigite detection method has a lower limit of detection than the traditionally used SIRM/χ parameter. It is also faster than FORC analysis and thus particularly suitable for analysis of large sample collections. Twenty greigite‐bearing layers were identified in the CE core using this method. The location of the Jaramillo subchron in the CE core is controversial in the currently available magnetostratigraphy, possibly related to the presence of greigite in this core interval.
Geodetic Matched Filter Slow Slip Event Detection Along the Northern Japan Subduction Zones
Authors: Marill Lou , Marsan David , Rousset Baptiste , Socquet Anne 
Published: August 2024

AbstractWe apply a template matching method on GNSS data for stations located in Honshu, Japan, to detect slow slip events associated with the subducting Philippine Sea and Pacific plates during the period from 1997 to 2020. A measure of the minimum detectable moment magnitude is proposed, from which we infer that the method could potentially detect SSEs as small as Mw 5.2 on the westernmost part of the Philippine Sea plate and Mw 6 on the Pacific plate below Honshu eastern coastline. We find 12 slow slip events on the Philippine Sea plate, among which eight are located on the known Boso slow slip event asperity and the four others are located offshore north‐east relative to the Boso SSEs, at the transition with the Pacific plate. We find 9 SSEs on the Pacific plate, mainly on the northern section, offshore Iwate prefecture. A clear gap with no SSEs coincides with the main asperity that broke during the 2011 Tohoku earthquake. Most event locations correlate with low locking areas. We do not find any clear temporal pattern apart from the regular occurrence of the largest Boso SSEs.
Assimilating Morning, Evening, and Nighttime Greenhouse Gas Observations in Atmospheric Inversions
Authors: Monteiro V. C. , Turnbull J. C. , Miles N. L. , Davis K. J. , Barkley Z. , Deng A. 
Published: August 2024

AbstractImproved urban greenhouse gas (GHG) flux estimates are crucial for informing policy and mitigation efforts. Atmospheric inversion modeling (AIM) is a widely used technique combining atmospheric measurements of trace gas, meteorological modeling, and a prior emission map to infer fluxes. Traditionally, AIM relies on mid‐afternoon observations due to the well‐represented atmospheric boundary layer in meteorological models. However, confining flux assessment to daytime observations is problematic for the urban scale, where air masses typically move over a city in a few hours and AIM therefore cannot provide improved constraints on emissions over the full diurnal cycle. We hypothesized that there are atmospheric conditions beyond the mid‐afternoon under which meteorological models also perform well. We tested this hypothesis using tower‐based measurements of CO2 and CH4, wind speed observations, weather model outputs from INFLUX (Indianapolis Flux Experiment), and a prior emissions map. By categorizing trace gas vertical gradients according to wind speed classes and identifying when the meteorological model satisfactorily simulates boundary layer depth (BLD), we found that non‐afternoon observations can be assimilated when wind speed is >5 m/s. This condition resulted in small modeled BLD biases (<40%) when compared to calmer conditions (>100%). For Indianapolis, 37% of the GHG measurements meet this wind speed criterion, almost tripling the observations retained for AIM. Similar results are expected for windy cities like Auckland, Melbourne, and Boston, potentially allowing AIM to assimilate up to 60% of the total (24‐hr) observations. Incorporating these observations in AIMs should yield a more diurnally comprehensive evaluation of urban GHG emissions.
“How to Save a Life”: A Premortem for Pediatric Digital Health
Authors: Psihogios Alexandra M. , Moscato Emily L. , Cummings Caroline , Canter Kimberly S. , Chen Diane , Coburn Shayna , Duncan Christina L. , Eaton Cyd K. , Essner Bonnie S. , Hannan Sinead , Ortega Adrian , Sayegh Caitlin S. , Stiles-Shields Colleen 
Published: August 2024

Objective: Digital health tools (e.g., apps, text messaging, telehealth, and social media) have been employed with pediatric populations for approximately two decades. As such, digital health is a scientifically mature field, ready for critical evaluation of the challenges and opportunities of using technology to equitably improve child health and health care. This commentary describes the application of a premortem exercise to forecast failures (i.e., “causes of death”) of pediatric digital health and strategies to prevent them. Method: With a convenience sample of trainees and early-, mid-, and later-career pediatric psychology professionals interested in digital health ( n = 14), we conducted a one-time, premortem exercise (i.e., a collaborative discussion to envision a failure and work backward) to brainstorm potential threats and opportunities for advancing pediatric digital health. Results: We came to consensus on five core themes related to digital health threats and opportunities: (a) We became stuck in proving efficacy and did not make an impact; (b) We assumed we knew more than youth and their families; (c) We replicated, exacerbated, or created new disparities compared to in-person care; (d) We underestimated the importance of a human touch; and (e) We did not know how to advocate for digital health as a clinical transformation. Conclusion: This commentary serves as a discussion point for identifying the strategic priorities of today (e.g., designing tools collaboratively with youth, planning for clinical implementation from inception) that can advance the development and impact of digital health tools and services for pediatric populations. Implications for Impact Statement With input from pediatric psychologists who participated in a one-time “premortem” exercise (i.e., a collaborative discussion to envision the failure of digital health and work backward), this commentary reflects on today’s challenges and recommendations for promoting youth health via digital health approaches (e.g., apps).
Fully tunable Fabry-Pérot cavity based on MEMS Sagnac loop reflector with ultra-low static power consumption
Authors: Park Young Jae , Her Man Jae , Jeong Youngjae , Choi Dong Ju , Kim Dong Uk , Lim Min Gi , Hong Myung Seok , Kwon Hyug Su , Yu Kyoungsik , Han Sangyoon 
Published: August 2024

AbstractThe Fabry-Pérot interferometer, a fundamental component in optoelectronic systems, offers interesting applications such as sensors, lasers, and filters. In this work, we show a tunable Fabry-Pérot cavity consisting of tunable Sagnac loop reflectors (SLRs) and phase shifters based on electrostatic microelectromechanical (MEMS) actuator. The fabrication process of the device is compatible with the standard wafer-level silicon photonics fabrication processes. This electrostatic actuation mechanism provides well-balanced, scalable pathways for efficient tuning methodologies. The extinction ratio of the continuously tunable SLRs’ reflectivity is larger than 20 dB. Full 2π phase shifting is achieved, and response times of all the components are less than 25 μs. Both actuators have extremely low static power, measuring under 20 fW and the energy needed for tuning is both below 20 pJ.