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1100 Days in the Life of the Supernova 2018ibb – the Best Pair-Instability Supernova Candidate, to date

Abstract (Expand)

Stars with ZAMS masses between 140 and 260M⊙ are thought to explode as pair-instability supernovae (PISNe). During their thermonuclear runaway, PISNe can produce up to several tens of solar masses of … radioactive nickel, resulting in luminous transients similar to some superluminous supernovae (SLSNe). Yet, no unambiguous PISN has been discovered so far. SN2018ibb is a H-poor SLSN at z=0.166 that evolves extremely slowly compared to the hundreds of known SLSNe. Between mid 2018 and early 2022, we monitored its photometric and spectroscopic evolution from the UV to the NIR with 2-10m class telescopes. SN2018ibb radiated >3×1051erg during its evolution, and its bolometric light curve reached >2×1044ergs−1 at peak. The long-lasting rise of >93 rest-frame days implies a long diffusion time, which requires a very high total ejected mass. The PISN mechanism naturally provides both the energy source (56Ni) and the long diffusion time. Theoretical models of PISNe make clear predictions for their photometric and spectroscopic properties. SN2018ibb complies with most tests on the light curves, nebular spectra and host galaxy, potentially all tests with the interpretation we propose. Both the light curve and the spectra require 25-44 M⊙ of freshly nucleosynthesised 56Ni, pointing to the explosion of a metal-poor star with a He-core mass of 120-130 M⊙ at the time of death. This interpretation is also supported by the tentative detection of [Co II]λ1.025μm, which has never been observed in any other PISN candidate or SLSN before. Powering by a central engine, such as a magnetar or a black hole, can be excluded with high confidence. This makes SN2018ibb by far the best candidate for being a PISN, to date.

Authors: Steve Schulze, Claes Fransson, Alexandra Kozyreva, Ting-Wan Chen, Ofer Yaron, Anders Jerkstrand, Avishay Gal-Yam, Jesper Sollerman, Lin Yan, Tuomas Kangas, Giorgos Leloudas, Conor M. B. Omand, Stephen J. Smartt, Yi Yang, Matt Nicholl, Nikhil Sarin, Yuhan Yao, Thomas G. Brink, Amir Sharon, Andrea Rossi, Ping Chen, Zhihao Chen, Aleksandar Cikota, Kishalay De, Andrew J. Drake, Alexei V. Filippenko, Christoffer Fremling, Laurane Freour, Johan P. U. Fynbo, Anna Y. Q. Ho, Cosimo Inserra, Ido Irani, Hanindyo Kuncarayakti, Ragnhild Lunnan, Paolo Mazzali, Eran O. Ofek, Eliana Palazzi, Daniel A. Perley, Miika Pursiainen, Barry Rothberg, Luke J. Shingles, Ken Smith, Kirsty Taggart, Leonardo Tartaglia, WeiKang Zheng, Joseph P. Anderson, Letizia Cassara, Eric Christensen, S. George Djorgovski, Lluis Galbany, Anamaria Gkini, Matthew J. Graham, Mariusz Gromadzki, Steven L. Groom, Daichi Hiramatsu, D. Andrew Howell, Mansi M. Kasliwal, Curtis McCully, Tomas E. Müller-Bravo, Simona Paiano, Emmanouela Paraskeva, Priscila J. Pessi, David Polishook, Arne Rau, Mickael Rigault, Ben Rusholme

Date Published: 1st May 2023

Publication Type: Journal

1100 Days in the Life of the Supernova 2018ibb – the Best Pair-Instability Supernova Candidate, to date

Abstract

Not specified

Authors: Steve Schulze, Claes Fransson, Alexandra Kozyreva, Ting-Wan Chen, Ofer Yaron, Anders Jerkstrand, Avishay Gal-Yam, Jesper Sollerman, Lin Yan, Tuomas Kangas, Giorgos Leloudas, Conor M. B. Omand, Stephen J. Smartt, Yi Yang, Matt Nicholl, Nikhil Sarin, Yuhan Yao, Thomas G. Brink, Amir Sharon, Andrea Rossi, Ping Chen, Zhihao Chen, Aleksandar Cikota, Kishalay De, Andrew J. Drake, Alexei V. Filippenko, Christoffer Fremling, Laurane Freour, Johan P. U. Fynbo, Anna Y. Q. Ho, Cosimo Inserra, Ido Irani, Hanindyo Kuncarayakti, Ragnhild Lunnan, Paolo Mazzali, Eran O. Ofek, Eliana Palazzi, Daniel A. Perley, Miika Pursiainen, Barry Rothberg, Luke J. Shingles, Ken Smith, Kirsty Taggart, Leonardo Tartaglia, WeiKang Zheng, Joseph P. Anderson, Letizia Cassara, Eric Christensen, S. George Djorgovski, Lluis Galbany, Anamaria Gkini, Matthew J. Graham, Mariusz Gromadzki, Steven L. Groom, Daichi Hiramatsu, D. Andrew Howell, Mansi M. Kasliwal, Curtis McCully, Tomas E. Müller-Bravo, Simona Paiano, Emmanouela Paraskeva, Priscila J. Pessi, David Polishook, Arne Rau, Mickael Rigault, Ben Rusholme

Date Published: 1st May 2023

Publication Type: Journal

SN 2021zny: an early flux excess combined with late-time oxygen emission suggests a double white dwarf merger event

Abstract

Not specified

Authors: Georgios Dimitriadis, Kate Maguire, Viraj R. Karambelkar, Ryan J. Lebron, Chang Liu, Alexandra Kozyreva, Adam A. Miller, Ryan Ridden-Harper, Joseph P. Anderson, Ting-Wan Chen, Michael Coughlin, Massimo Della Valle, Andrew Drake, Lluı́s Galbany, Mariusz Gromadzki, Steven L. Groom, Claudia P. Gutiérrez, Nada Ihanec, Cosimo Inserra, Joel Johansson, Tomás E. Müller-Bravo, Matt Nicholl, Abigail Polin, Ben Rusholme, Steve Schulze, Jesper Sollerman, Shubham Srivastav, Kirsty Taggart, Qinan Wang, Yi Yang, David R. Young

Date Published: 1st May 2023

Publication Type: Journal

Testing angular momentum transport processes with asteroseismology of solar-type main-sequence stars

Abstract (Expand)

Context: Thanks to the so-called photometry revolution with the space-based missions CoRoT, Kepler, and TESS, asteroseismology has become a powerful tool to study the internal rotation of stars. The … rotation rate depends on the efficiency of the angular momentum (AM) transport inside the star, and its study allows to constrain the internal AM transport processes, as well as improve our understanding of their physical nature. Aims: We compared the ratio of the rotation rate predicted by asteroseismology and starspot measurements of solar-type stars considering different AM transport prescriptions and investigated whether some of these prescriptions can be ruled out observationally. Methods: We conducted a two-step modelling procedure of four main-sequence stars from the Kepler LEGACY sample, which consists of an asteroseismic characterisation that serves as a guide for a modelling with rotating models, including a detailed and coherent treatment of the AM transport. The rotation profiles derived with this procedure were used to estimate the ratio of the mean asteroseismic rotation rate with the surface rotation rate from starspot measurements for each AM transport prescriptions. Comparisons between the models were then conducted. Results: In the hotter part of the Hertzsprung-Russell (HR) diagram (masses typically above ∼1.2 M⊙ at solar metallicity), models with only hydrodynamic transport processes and models with additional transport by magnetic instabilities are found to be consistent with previous measurements that observed a low degree (below 30%) of radial differential rotation between the radiative and convective zones. For these stars, which constitute a significant fraction of the Kepler LEGACY sample, a combination of asteroseismic constraints from the splitting of pressure modes and of the surface rotation rate does not allow us to conclude that an efficient AM transport is required in addition to transport by meridional circulation and shear instability alone. Even a model assuming local AM conservation cannot be ruled out. In the colder part of the HR diagram, the situation is different because of the efficient braking of the stellar surface by magnetised winds. We find a clear disagreement between the rotational properties of models that only include hydrodynamic processes and asteroseismic constraints, while models with magnetic fields correctly reproduce the observations, similarly to the solar case. Conclusions: This shows the existence of a mass regime corresponding to main-sequence F-type stars for which it is difficult to constrain the AM transport processes, unlike for hotter, Gamma Dor stars or colder, less massive solar analogues. The comparison between asteroseismic measurements and surface rotation rates enables us to easily rule out models with an inefficient transport of AM in the colder part of the HR diagram.

Authors: J. Bétrisey, P. Eggenberger, G. Buldgen, O. Benomar, M. Bazot

Date Published: 1st May 2023

Publication Type: Journal

Beyond the imitation game: Quantifying and extrapolating the capabilities of language models

Abstract

Not specified

Authors: Aarohi Srivastava, Abhinav Rastogi, Abhishek Rao, ..., Michael Strube, .., and_another_400_something_other_authors

Date Published: 1st May 2023

Publication Type: Journal

Parallel Inference of Phylogenetic Stands with Gentrius

Abstract

Not specified

Authors: Anastasis Togkousidis, Olga Chernomor, Alexandros Stamatakis

Date Published: 1st May 2023

Publication Type: Proceedings

Finite element approximation of dielectrophoretic force driven flow problems

Abstract (Expand)

In this paper, we propose a full discretization scheme for the instationary thermal-electro-hydrodynamic (TEHD) Boussinesq equations. These equations model the dynamics of a non-isothermal, dielectric …f a non-isothermal, dielectric fluid under the influence of a dielectrophoretic (DEP) force. Our scheme combines an H 1 -conformal finite element method for spatial discretization with a backward differentiation formula (BDF) for time stepping. The resulting scheme allows for a decoupled solution of the individual parts of this multi-physics system. Moreover, we derive a priori convergence rates that are of first and second order in time, depending on how the individual ingredients of the BDF scheme are chosen and of optimal order in space. In doing so, special care is taken of modeling the DEP force, since its original form is a cubic term. The obtained error estimates are verified by numerical experiments.

Authors: Philipp Gerstner, Vincent Heuveline

Date Published: 1st May 2023

Publication Type: Journal

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