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1697 Publications visible to you, out of a total of 1697
Simulated analogues I: apparent and physical evolution of young binary protostellar systems

Abstract (Expand)

ABSTRACT Protostellar binaries harbour complex environment morphologies. Observations represent a snapshot in time, and projection and optical depth effects impair our ability to interpret them. Careful …to interpret them. Careful comparison with high-resolution models that include the larger star-forming region can help isolate the driving physical processes and give context in the time domain to the observations. We carry out four zoom-in simulations with au scale resolution that result in three binaries and a single star. For the first time ever, we follow the detailed evolution of a protobinary in a full molecular cloud context until a circumbinary disc forms. We investigate the gas dynamics around the young stars and extract disc sizes. Using radiative transfer, we obtain the evolutionary tracer Tbol of the binary systems. We find that the centrifugal radius in prestellar cores is a poor estimator of the resulting disc size due to angular momentum transport at all scales. For binaries, the disc sizes are regulated periodically by the binary orbit, having larger radii close to the apastron. The bolometric temperature differs systematically between edge-on and face-on views and shows a high-frequency time dependence correlated with the binary orbit and a low-frequency time dependence with larger episodic accretion events. These oscillations can cause the appearance of the system to change rapidly from class 0 to class I and, for short periods, even bring it to class II. The highly complex structure in early stages, as well as the binary orbit itself, affects the classical interpretation of protostellar classes, and the direct translation to evolutionary stages has to be done with caution and include other evolutionary indicators such as the extent of envelope material.

Authors: Vito Tuhtan, Rami Al-Belmpeisi, Mikkel Bregning Christensen, Rajika Kuruwita, Troels Haugbølle

Date Published: 1st Nov 2024

Publication Type: Journal

Simulated analogues II: a new methodology for non-parametric matching of models to observations

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ABSTRACT Star formation is a multiscale problem, and only global simulations that account for the connection from the molecular cloud-scale gas flow to the accreting protostar can reflect the observed …r can reflect the observed complexity of protostellar systems. Star-forming regions are characterized by supersonic turbulence, and as a result, it is not possible to simultaneously design models that account for the larger environment and in detail reproduce observed stellar systems. Instead, the stellar inventories can be matched statistically, and the best matches found that approximate specific observations. Observationally, a combination of single-dish telescopes and interferometers are now able to resolve the nearest protostellar objects on all scales from the protostellar core to the inner $10\, \mathrm{au}$. We present a new non-parametric methodology which uses high-resolution simulations and post-processing methods to match simulations and observations using deep learning. Our goal is to perform a down-selection from large data sets of synthetic images to a ranked list of best-matching candidates with respect to the observation. This is particularly useful for binary and multiple stellar systems that form in turbulent environments. The objective is to accelerate the rate at which we can do such comparisons, remove biases from hand-picking matches, and contribute to identifying the underlying physical processes that drive the creation and evolution of observed protostellar systems.

Authors: Rami Al-Belmpeisi, Vito Tuhtan, Mikkel Bregning Christensen, Rajika Kuruwita, Troels Haugbølle

Date Published: 1st Nov 2024

Publication Type: Journal

From spherical stars to disk-like structures: 3D common-envelope evolution of massive binaries beyond inspiral

Abstract

Not specified

Authors: Marco Vetter, Friedrich K. Röpke, Fabian R. N. Schneider, Rüdiger Pakmor, Sebastian T. Ohlmann, Mike Y. M. Lau, Robert Andrassy

Date Published: 1st Nov 2024

Publication Type: Journal

Large-scale ordered magnetic fields generated in mergers of helium white dwarfs

Abstract

Not specified

Authors: Rüdiger Pakmor, Ingrid Pelisoli, Stephen Justham, Abinaya S. Rajamuthukumar, Friedrich K. Röpke, Fabian R. N. Schneider, Selma E. de Mink, Sebastian T. Ohlmann, Philipp Podsiadlowski, Javier Morán-Fraile, Marco Vetter, Robert Andrassy

Date Published: 1st Nov 2024

Publication Type: Journal

Expected insights into Type Ia supernovae from LISA’s gravitational wave observations

Abstract

Not specified

Authors: Valeriya Korol, Riccardo Buscicchio, Ruediger Pakmor, Javier Morán-Fraile, Christopher J. Moore, Selma E. de Mink

Date Published: 1st Nov 2024

Publication Type: Journal

Stripped Helium Star and Compact Object Binaries in Coeval Populations: Predictions Based on Detailed Binary Evolution Models

Abstract (Expand)

Abstract Massive stars mainly form in close binaries, where their mutual interactions can profoundly alter their evolutionary paths. Evolved binaries consisting of a massive OB-type main-sequence star …OB-type main-sequence star with a stripped helium star or a compact companion represent a crucial stage in the evolution toward double compact objects, whose mergers are (potentially) detectable via gravitational waves. The recent detection of X-ray-quiet OB+black hole binaries and OB+stripped helium star binaries has set the stage for discovering more of these systems in the near future. In this work, based on 3670 detailed binary-evolution models and using empirical distributions of initial binary parameters, we compute the expected population of such evolved massive binaries in coeval stellar populations, including stars in star clusters and in galaxies with starburst activities, for ages up to 100 Myr. Our results are vividly illustrated in an animation that shows the evolution of these binaries in the color–magnitude diagram over time. We find that the number of OB+black hole binaries peaks around 10 Myr, and OB+neutron star binaries are most abundant at approximately 20 Myr. Both black holes and neutron stars can potentially be found in populations with ages up to 90 Myr. Additionally, we analyze the properties of such binaries at specific ages. We find that OB+helium stars and OB+black hole binaries are likely to be identifiable as single-lined spectroscopic binaries. Our research serves as a guide for future observational efforts to discover such binaries in young star clusters and starburst environments.

Authors: Chen Wang, Julia Bodensteiner, Xiao-Tian Xu, Selma E. de Mink, Norbert Langer, Eva Laplace, Alejandro Vigna-Gómez, Stephen Justham, Jakub Klencki, Aleksandra Olejak, Ruggero Valli, Abel Schootemeijer

Date Published: 30th Oct 2024

Publication Type: Journal

The accomplices: Heparan sulfates and N-glycans foster SARS-CoV-2 spike:ACE2 receptor binding and virus priming

Abstract (Expand)

Although it is well established that the SARS-CoV-2 spike glycoprotein binds to the host cell ACE2 receptor to initiate infection, far less is known about the tissue tropism and host cell susceptibility …susceptibility to the virus. Differential expression across different cell types of heparan sulfate (HS) proteoglycans, with variably sulfated glycosaminoglycans (GAGs), and their synergistic interactions with host and viral N-glycans may contribute to tissue tropism and host cell susceptibility. Nevertheless, their contribution remains unclear since HS and N-glycans evade experimental characterization. We, therefore, carried out microsecond-long all-atom molecular dynamics simulations, followed by random acceleration molecular dynamics simulations, of the fully glycosylated spike:ACE2 complex with and without highly sulfated GAG chains bound. By considering the model GAGs as surrogates for the highly sulfated HS expressed in lung cells, we identified key cell entry mechanisms of spike SARS-CoV-2. We find that HS promotes structural and energetic stabilization of the active conformation of the spike receptor-binding domain (RBD) and reorientation of ACE2 toward the N-terminal domain in the same spike subunit as the RBD. Spike and ACE2 N-glycans exert synergistic effects, promoting better packing, strengthening the protein:protein interaction, and prolonging the residence time of the complex. ACE2 and HS binding trigger rearrangement of the S2’ functional protease cleavage site through allosteric interdomain communication. These results thus show that HS has a multifaceted role in facilitating SARS-CoV-2 infection, and they provide a mechanistic basis for the development of GAG derivatives with anti-SARS-CoV-2 potential.

Authors: Giulia Paiardi, Matheus Ferraz, Marco Rusnati, Rebecca C. Wade

Date Published: 22nd Oct 2024

Publication Type: Journal

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