@article{13457, abstract = {Context. Observations of massive stars in open clusters younger than ∼8 Myr have shown that a majority of them are in binary systems, most of which will interact during their life. While these can be used as a proxy of the initial multiplicity properties, studying populations of massive stars older than ∼20 Myr allows us to probe the outcome of these interactions after a significant number of systems have experienced mass and angular momentum transfer and may even have merged. Aims. Using multi-epoch integral-field spectroscopy, we aim to investigate the multiplicity properties of the massive-star population in the dense core of the ∼40 Myr old cluster NGC 330 in the Small Magellanic Cloud in order to search for possible imprints of stellar evolution on the multiplicity properties. Methods. We obtained six epochs of VLT/MUSE observations operated in wide-field mode with the extended wavelength setup and supported by adaptive optics. We extracted spectra and measured radial velocities for stars brighter than mF814W = 19. We identified single-lined spectroscopic binaries through significant RV variability with a peak-to-peak amplitude larger than 20 km s−1. We also identified double-lined spectroscopic binaries, and quantified the observational biases for binary detection. In particular, we took into account that binary systems with similar line strengths are difficult to detect in our data set. Results. The observed spectroscopic binary fraction among stars brighter than mF814W = 19 (approximately 5.5 M⊙ on the main sequence) is fSBobs = 13.2 ± 2.0%. Considering period and mass ratio ranges from log(P) = 0.15−3.5 (about 1.4 to 3160 d), q = 0.1−1.0, and a representative set of orbital parameter distributions, we find a bias-corrected close binary fraction of fcl = 34−7+8%. This fraction seems to decline for the fainter stars, which indicates either that the close binary fraction drops in the B-type domain, or that the period distribution becomes more heavily weighted toward longer orbital periods. We further find that both fractions vary strongly in different regions of the color-magnitude diagram, which corresponds to different evolutionary stages. This probably reveals the imprint of the binary history of different groups of stars. In particular, we find that the observed spectroscopic binary fraction of Be stars (fSBobs = 2 ± 2%) is significantly lower than that of B-type stars (fSBobs = 9 ± 2%). Conclusions. We provide the first homogeneous radial velocity study of a large sample of B-type stars at a low metallicity ([Fe/H] ≲ −1.0). The overall bias-corrected close binary fraction (log(P) < 3.5 d) of the B-star population in NGC 330 is lower than the fraction reported for younger Galactic and Large Magellanic Cloud clusters in previous works. More data are needed, however, to establish whether the observed differences are caused by an age or a metallicity effect.}, author = {Bodensteiner, J. and Sana, H. and Wang, C. and Langer, N. and Mahy, L. and Banyard, G. and de Koter, A. and de Mink, S. E. and Evans, C. J. and Götberg, Ylva Louise Linsdotter and Patrick, L. R. and Schneider, F. R. N. and Tramper, F.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, publisher = {EDP Sciences}, title = {{The young massive SMC cluster NGC 330 seen by MUSE. II. Multiplicity properties of the massive-star population}}, doi = {10.1051/0004-6361/202140507}, volume = {652}, year = {2021}, } @article{13455, abstract = {The majority of massive stars live in binary or multiple systems and will interact with a companion during their lifetimes, which helps to explain the observed diversity of core-collapse supernovae. Donor stars in binary systems can lose most of their hydrogen-rich envelopes through mass transfer. As a result, not only are the surface properties affected, but so is the core structure. However, most calculations of the core-collapse properties of massive stars rely on single-star models. We present a systematic study of the difference between the pre-supernova structures of single stars and stars of the same initial mass (11–21 M⊙) that have been stripped due to stable post-main-sequence mass transfer at solar metallicity. We present the pre-supernova core composition with novel diagrams that give an intuitive representation of the isotope distribution. As shown in previous studies, at the edge of the carbon-oxygen core, the binary-stripped star models contain an extended gradient of carbon, oxygen, and neon. This layer remains until core collapse and is more extended in mass for higher initial stellar masses. It originates from the receding of the convective helium core during core helium burning in binary-stripped stars, which does not occur in single-star models. We find that this same evolutionary phase leads to systematic differences in the final density and nuclear energy generation profiles. Binary-stripped star models have systematically higher total masses of carbon at the moment of core collapse compared to single-star models, which likely results in systematically different supernova yields. In about half of our models, the silicon-burning and oxygen-rich layers merge after core silicon burning. We discuss the implications of our findings for the “explodability”, supernova observations, and nucleosynthesis of these stars. Our models are publicly available and can be readily used as input for detailed supernova simulations.}, author = {Laplace, E. and Justham, S. and Renzo, M. and Götberg, Ylva Louise Linsdotter and Farmer, R. and Vartanyan, D. and de Mink, S. E.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, publisher = {EDP Sciences}, title = {{Different to the core: The pre-supernova structures of massive single and binary-stripped stars}}, doi = {10.1051/0004-6361/202140506}, volume = {656}, year = {2021}, } @article{13454, abstract = {Helium star–carbon-oxygen white dwarf (CO WD) binaries are potential single-degenerate progenitor systems of thermonuclear supernovae. Revisiting a set of binary evolution calculations using the stellar evolution code MESA, we refine our previous predictions about which systems can lead to a thermonuclear supernova and then characterize the properties of the helium star donor at the time of explosion. We convert these model properties to near-UV/optical magnitudes assuming a blackbody spectrum and support this approach using a matched stellar atmosphere model. These models will be valuable to compare with pre-explosion imaging for future supernovae, though we emphasize the observational difficulty of detecting extremely blue companions. The pre-explosion source detected in association with SN 2012Z has been interpreted as a helium star binary containing an initially ultra-massive WD in a multiday orbit. However, extending our binary models to initial CO WD masses of up to 1.2 M⊙, we find that these systems undergo off-center carbon ignitions and thus are not expected to produce thermonuclear supernovae. This tension suggests that, if SN 2012Z is associated with a helium star–WD binary, then the pre-explosion optical light from the system must be significantly modified by the binary environment and/or the WD does not have a carbon-rich interior composition.}, author = {Wong, Tin Long Sunny and Schwab, Josiah and Götberg, Ylva Louise Linsdotter}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {2}, publisher = {American Astronomical Society}, title = {{Pre-explosion properties of Helium star donors to thermonuclear supernovae}}, doi = {10.3847/1538-4357/ac27ae}, volume = {922}, year = {2021}, } @article{13453, abstract = {Most massive stars are born in binaries close enough for mass transfer episodes. These modify the appearance, structure, and future evolution of both stars. We compute the evolution of a 100-day-period binary, consisting initially of a 25 M⊙ star and a 17 M⊙ star, which experiences stable mass transfer. We focus on the impact of mass accretion on the surface composition, internal rotation, and structure of the accretor. To anchor our models, we show that our accretor broadly reproduces the properties of ζ Ophiuchi, which has long been proposed to have accreted mass before being ejected as a runaway star when the companion exploded. We compare our accretor to models of single rotating stars and find that the later and stronger spin-up provided by mass accretion produces significant differences. Specifically, the core of the accretor retains higher spin at the end of the main sequence, and a convective layer develops that changes its density profile. Moreover, the surface of the accretor star is polluted by CNO-processed material donated by the companion. Our models show effects of mass accretion in binaries that are not captured in single rotating stellar models. This possibly impacts the further evolution (either in a binary or as single stars), the final collapse, and the resulting spin of the compact object.}, author = {Renzo, M. and Götberg, Ylva Louise Linsdotter}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {2}, publisher = {American Astronomical Society}, title = {{Evolution of accretor stars in massive binaries: Broader implications from modeling ζ Ophiuchi}}, doi = {10.3847/1538-4357/ac29c5}, volume = {923}, year = {2021}, } @article{13996, abstract = {We report the observation of an anomalous nonlinear optical response of the prototypical three-dimensional topological insulator bismuth selenide through the process of high-order harmonic generation. We find that the generation efficiency increases as the laser polarization is changed from linear to elliptical, and it becomes maximum for circular polarization. With the aid of a microscopic theory and a detailed analysis of the measured spectra, we reveal that such anomalous enhancement encodes the characteristic topology of the band structure that originates from the interplay of strong spin–orbit coupling and time-reversal symmetry protection. The implications are in ultrafast probing of topological phase transitions, light-field driven dissipationless electronics, and quantum computation.}, author = {Baykusheva, Denitsa Rangelova and Chacón, Alexis and Lu, Jian and Bailey, Trevor P. and Sobota, Jonathan A. and Soifer, Hadas and Kirchmann, Patrick S. and Rotundu, Costel and Uher, Ctirad and Heinz, Tony F. and Reis, David A. and Ghimire, Shambhu}, issn = {1530-6992}, journal = {Nano Letters}, keywords = {Mechanical Engineering, Condensed Matter Physics, General Materials Science, General Chemistry, Bioengineering}, number = {21}, pages = {8970--8978}, publisher = {American Chemical Society}, title = {{All-optical probe of three-dimensional topological insulators based on high-harmonic generation by circularly polarized laser fields}}, doi = {10.1021/acs.nanolett.1c02145}, volume = {21}, year = {2021}, } @article{13997, abstract = {We investigate theoretically the strong-field regime of light-matter interactions in the topological-insulator class of quantum materials. In particular, we focus on the process of nonperturbative high-order harmonic generation from the paradigmatic three-dimensional topological insulator bismuth selenide (Bi2Se3) subjected to intense midinfrared laser fields. We analyze the contributions from the spin-orbit-coupled bulk states and the topological surface bands separately and reveal a major difference in how their harmonic yields depend on the ellipticity of the laser field. Bulk harmonics show a monotonic decrease in their yield as the ellipticity increases, in a manner reminiscent of high harmonic generation in gaseous media. However, the surface contribution exhibits a highly nontrivial dependence, culminating with a maximum for circularly polarized fields. We attribute the observed anomalous behavior to (i) the enhanced amplitude and the circular pattern of the interband dipole and the Berry connections in the vicinity of the Dirac point and (ii) the influence of the higher-order, hexagonal warping terms in the Hamiltonian, which are responsible for the hexagonal deformation of the energy surface at higher momenta. The latter are associated directly with spin-orbit-coupling parameters. Our results thus establish the sensitivity of strong-field-driven high harmonic emission to the topology of the band structure as well as to the manifestations of spin-orbit interaction.}, author = {Baykusheva, Denitsa Rangelova and Chacón, Alexis and Kim, Dasol and Kim, Dong Eon and Reis, David A. and Ghimire, Shambhu}, issn = {2469-9934}, journal = {Physical Review A}, number = {2}, publisher = {American Physical Society}, title = {{Strong-field physics in three-dimensional topological insulators}}, doi = {10.1103/physreva.103.023101}, volume = {103}, year = {2021}, } @article{13995, abstract = {Shape resonances play a central role in many areas of science, but the real-time measurement of the associated many-body dynamics remains challenging. Here, we present measurements of recoil frame angle-resolved photoionization delays in the vicinity of shape resonances of CF4. This technique provides insights into the spatiotemporal photoionization dynamics of molecular shape resonances. We find delays of up to ∼600 as in the ionization out of the highest occupied molecular orbital (HOMO) with a strong dependence on the emission direction and a pronounced asymmetry along the dissociation axis. Comparison with quantum-scattering calculations traces the asymmetries to the interference of a small subset of partial waves at low kinetic energies and, additionally, to the interference of two overlapping shape resonances in the HOMO-1 channel. Our experimental and theoretical results establish a broadly applicable approach to space- and time-resolved photoionization dynamics in the molecular frame.}, author = {Heck, Saijoscha and Baykusheva, Denitsa Rangelova and Han, Meng and Ji, Jia-Bao and Perry, Conaill and Gong, Xiaochun and Wörner, Hans Jakob}, issn = {2375-2548}, journal = {Science Advances}, keywords = {Multidisciplinary}, number = {49}, publisher = {American Association for the Advancement of Science}, title = {{Attosecond interferometry of shape resonances in the recoil frame of CF4}}, doi = {10.1126/sciadv.abj8121}, volume = {7}, year = {2021}, } @unpublished{14097, abstract = {UVEX is a proposed medium class Explorer mission designed to provide crucial missing capabilities that will address objectives central to a broad range of modern astrophysics. The UVEX design has two co-aligned wide-field imagers operating in the FUV and NUV and a powerful broadband medium resolution spectrometer. In its two-year baseline mission, UVEX will perform a multi-cadence synoptic all-sky survey 50/100 times deeper than GALEX in the NUV/FUV, cadenced surveys of the Large and Small Magellanic Clouds, rapid target of opportunity followup, as well as spectroscopic followup of samples of stars and galaxies. The science program is built around three pillars. First, UVEX will explore the low-mass, low-metallicity galaxy frontier through imaging and spectroscopic surveys that will probe key aspects of the evolution of galaxies by understanding how star formation and stellar evolution at low metallicities affect the growth and evolution of low-metallicity, low-mass galaxies in the local universe. Such galaxies contain half the mass in the local universe, and are analogs for the first galaxies, but observed at distances that make them accessible to detailed study. Second, UVEX will explore the dynamic universe through time-domain surveys and prompt spectroscopic followup capability will probe the environments, energetics, and emission processes in the early aftermaths of gravitational wave-discovered compact object mergers, discover hot, fast UV transients, and diagnose the early stages of stellar explosions. Finally, UVEX will become a key community resource by leaving a large all-sky legacy data set, enabling a wide range of scientific studies and filling a gap in the new generation of wide-field, sensitive optical and infrared surveys provided by the Rubin, Euclid, and Roman observatories. This paper discusses the scientific potential of UVEX, and the broad scientific program.}, author = {Kulkarni, S. R. and Harrison, Fiona A. and Grefenstette, Brian W. and Earnshaw, Hannah P. and Andreoni, Igor and Berg, Danielle A. and Bloom, Joshua S. and Cenko, S. Bradley and Chornock, Ryan and Christiansen, Jessie L. and Coughlin, Michael W. and Criswell, Alexander Wuollet and Darvish, Behnam and Das, Kaustav K. and De, Kishalay and Dessart, Luc and Dixon, Don and Dorsman, Bas and Kareem El-Badry, Kareem El-Badry and Evans, Christopher and Ford, K. E. Saavik and Fremling, Christoffer and Gansicke, Boris T. and Gezari, Suvi and Götberg, Ylva Louise Linsdotter and Green, Gregory M. and Graham, Matthew J. and Heida, Marianne and Ho, Anna Y. Q. and Jaodand, Amruta D. and Christopher M. Johns-Krull, Christopher M. Johns-Krull and Kasliwal, Mansi M. and Lazzarini, Margaret and Lu, Wenbin and Margutti, Raffaella and Martin, D. Christopher and Masters, Daniel Charles and McKernan, Barry and Naze, Yael and Nissanke, Samaya M. and Parazin, B. and Perley, Daniel A. and Phinney, E. Sterl and Piro, Anthony L. and Raaijmakers, G. and Rauw, Gregor and Rodriguez, Antonio C. and Sana, Hugues and Senchyna, Peter and Singer, Leo P. and Spake, Jessica J. and Stassun, Keivan G. and Stern, Daniel and Teplitz, Harry I. and Weisz, Daniel R. and Yao, Yuhan}, booktitle = {arXiv}, title = {{Science with the ultraviolet explorer (UVEX)}}, doi = {10.48550/arXiv.2111.15608}, year = {2021}, } @article{10005, abstract = {We study systems of nonlinear partial differential equations of parabolic type, in which the elliptic operator is replaced by the first-order divergence operator acting on a flux function, which is related to the spatial gradient of the unknown through an additional implicit equation. This setting, broad enough in terms of applications, significantly expands the paradigm of nonlinear parabolic problems. Formulating four conditions concerning the form of the implicit equation, we first show that these conditions describe a maximal monotone p-coercive graph. We then establish the global-in-time and large-data existence of a (weak) solution and its uniqueness. To this end, we adopt and significantly generalize Minty’s method of monotone mappings. A unified theory, containing several novel tools, is developed in a way to be tractable from the point of view of numerical approximations.}, author = {Bulíček, Miroslav and Maringová, Erika and Málek, Josef}, issn = {1793-6314}, journal = {Mathematical Models and Methods in Applied Sciences}, keywords = {Nonlinear parabolic systems, implicit constitutive theory, weak solutions, existence, uniqueness}, number = {09}, publisher = {World Scientific}, title = {{On nonlinear problems of parabolic type with implicit constitutive equations involving flux}}, doi = {10.1142/S0218202521500457}, volume = {31}, year = {2021}, } @inproceedings{10553, abstract = {The popularity of permissioned blockchain systems demands BFT SMR protocols that are efficient under good network conditions (synchrony) and robust under bad network conditions (asynchrony). The state-of-the-art partially synchronous BFT SMR protocols provide optimal linear communication cost per decision under synchrony and good leaders, but lose liveness under asynchrony. On the other hand, the state-of-the-art asynchronous BFT SMR protocols are live even under asynchrony, but always pay quadratic cost even under synchrony. In this paper, we propose a BFT SMR protocol that achieves the best of both worlds -- optimal linear cost per decision under good networks and leaders, optimal quadratic cost per decision under bad networks, and remains always live.}, author = {Gelashvili, Rati and Kokoris Kogias, Eleftherios and Spiegelman, Alexander and Xiang, Zhuolun}, booktitle = {Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing}, isbn = {9-781-4503-8548-0}, keywords = {optimal, state machine replication, fallback, asynchrony, byzantine faults}, location = {Virtual, Italy}, pages = {187--190}, publisher = {Association for Computing Machinery}, title = {{Brief announcement: Be prepared when network goes bad: An asynchronous view-change protocol}}, doi = {10.1145/3465084.3467941}, year = {2021}, }