arXiv subjects

Tenley Hutchinson-Smith

Publications and source records attributed to Tenley Hutchinson-Smith.

5 recordsLinked to original sources

arXiv2026

Hydrodynamic Response of Mildly Evolved Common Envelope Donors in Luminous Red Novae

Luminous red novae trace unstable binary interactions in which common-envelope evolution can produce either a stellar merger or a surviving binary following envelope ejection. Recent population studies suggest that a substantial fraction of these systems originate from mildly evolved donors whose structures occupy an intermediate regime between simplified polytropic envelopes and highly stratified giant stars. We present a suite of three-dimensional hydrodynamic simulations of mildly evolved donors interacting with embedded companions spanning a range of mass ratios and central density concentrations. We show that the hydrodynamic evolution is strongly regulated by the donor central concentration, parameterized by the ratio $ρ_c/\barρ$. Donors with similar values of $ρ_c/\barρ$ exhibit similar inspiral morphologies and mass-ejection histories despite substantial differences in stellar mass and radius. Systems with relatively modest central concentration undergo rapid inspiral dominated by local orbital-energy deposition, while more centrally concentrated donors develop prolonged expansion-driven phases in which shocks and large-scale envelope motions redistribute deposited energy and angular momentum throughout the star. In this regime, the envelope itself becomes dynamically important in driving continued mass loss long after the rapid plunge-in phase slows. These results challenge semi-analytic models of luminous red novae that assume nearly instantaneous envelope ejection and suggest that their observed diversity may depend not only on total ejecta mass, but also on the temporal structure of the outflow.

astro-ph.SR↗

arXiv2026

Galaxy Zoo Bar Lengths: A Catalogue of Measurements from Hubble Space Telescope Images and the Evolution of Galactic Bar Structure at z < 1

Understanding the role of galactic scale bars in disk galaxy evolution requires detailed measurements of bar properties across galaxies hosting bars at many redshifts. We present measurements of bar lengths and widths in a sample of 8230 disk galaxies from Hubble Space Telescope (HST) Legacy surveys. The highest-redshift barred galaxies in the sample have $z \sim 3$; most have $z \leq 1$. Using a mass-complete sample from the COSMOS field, we examine bar properties and evolution within $0.25 < z < 1$ in galaxies with stellar mass $\log(M_{\ast}/M_{\odot}) \geq 9.5$. The lowest-mass galaxies in our sample have similar star formation rate (SFR) distributions whether or not they host bars. For galaxies with $\log(M_{\ast}/M_{\odot}) \geq 10$, barred galaxies are more likely to be quiescent or quenched, consistent with bars mainly participating in slow quenching processes. The median physical bar length increases with increasing stellar mass. Relative bar lengths and widths (as a fraction of disk radius) peak at stellar mass $\log(M_{\ast}/M_{\odot}) \sim 10.25$, and change together with mass such that the median ratio, a proxy for bar strength, does not significantly change with stellar mass. Bars in our sample tend to be slightly ($\approx 13$%) weaker at higher redshift. Quiescent and quenching galaxies have longer and wider bars than those in galaxies on or above the star-forming sequence, especially at lower redshift and higher masses; at the low-mass end of our sample, starburst galaxies host relatively longer and stronger bars. Our findings are consistent with other results from studies at both higher and lower redshift, cementing the fundamental importance of bars in disk galaxy evolution.

astro-ph.GA↗

arXiv2024

Rethinking Thorne-Żytkow Object Formation: The Fate of X-ray Binary LMC X-4 and Implications for Ultra-long Gamma-ray Bursts

We present a start-to-end simulation aimed at studying the long-term fate of high-mass X-ray binaries and whether a Thorne-Żytkow object (TŻO) might ultimately be assembled. We analyze results from a 3D hydrodynamical simulation that models the eventual fate of LMC X-4, a compact high-mass X-ray binary system, after the primary fills its Roche lobe and engulfs the neutron star companion. We discuss the outcome of this engulfment within the standard paradigm of TŻO formation. The post-merger angular momentum content of the stellar core is a key ingredient, as even a small amount of rotation can break spherical symmetry and produce a centrifugally supported accretion disk. Our findings suggest the inspiraling neutron star, upon merging with the core, can accrete efficiently via a disk at high rates ($\approx 10^{-2}M_\odot/{\rm s}$), subsequently collapsing into a black hole and triggering a bright transient with a luminosity and duration typical of an ultra-long gamma-ray burst. We propose that the canonical framework for TŻO formation via common envelope needs to be revised, as the significant post-merger accretion feedback will unavoidably unbind the vast majority of the surrounding envelope.

astro-ph.HE↗

arXiv2024

Rethinking Thorne-Żytkow Object Formation: Assembly via Common Envelope in Field Binaries

Thorne-Żytkow objects (TŻOs), hypothetical merger products in which a neutron star is embedded in a stellar core, are traditionally considered steady-state configurations. Their assembly, especially through dynamical channels, is not well-understood. The predominant focus in the literature has been on the observational signatures related to the evolution and long-term fate of TŻOs, with their initial formation often treated as a given. However, the foundational calculations supporting the existence of TŻOs assume non-rotating spherically-symmetric initial conditions that we find to be inconsistent with a binary merger scenario. In this work, we explore the implications of post-merger dynamics in TŻO formation scenarios with field binary progenitors, specifically the role that angular momentum transport during the common envelope phase plays in constraining possible merger products, using the tools of stellar evolution and three-dimensional hydrodynamics. We also propose an alternative steady-state outcome for these mergers: the thin-envelope TŻO, an equilibrium solution consisting of a low-mass spherical envelope supported by the accretion disk luminosity of a central stellar-mass black hole. These configurations may be of interest to upcoming time-domain surveys as potential X-ray sources that may be preceded by a series of bright transient events.

astro-ph.HE↗

arXiv2022

Successful Common Envelope Ejection and Binary Neutron Star Formation in 3D Hydrodynamics

A binary neutron star merger has been observed in a multi-messenger detection of gravitational wave (GW) and electromagnetic (EM) radiation. Binary neutron stars that merge within a Hubble time, as well as many other compact binaries, are expected to form via common envelope evolution. Yet five decades of research on common envelope evolution have not yet resulted in a satisfactory understanding of the multi-spatial multi-timescale evolution for the systems that lead to compact binaries. In this paper, we report on the first successful simulations of common envelope ejection leading to binary neutron star formation in 3D hydrodynamics. We simulate the dynamical inspiral phase of the interaction between a 12$M_\odot$ red supergiant and a 1.4$M_\odot$ neutron star for different initial separations and initial conditions. For all of our simulations, we find complete envelope ejection and final orbital separations of $a_{\rm f} \approx 1.3$-$5.1 R_\odot$ depending on the simulation and criterion, leading to binary neutron stars that can merge within a Hubble time. We find $α_{\rm CE}$-equivalent efficiencies of $\approx 0.1$-$2.7$ depending on the simulation and criterion, but this may be specific for these extended progenitors. We fully resolve the core of the star to $\lesssim 0.005 R_\odot$ and our 3D hydrodynamics simulations are informed by an adjusted 1D analytic energy formalism and a 2D kinematics study in order to overcome the prohibitive computational cost of simulating these systems. The framework we develop in this paper can be used to simulate a wide variety of interactions between stars, from stellar mergers to common envelope episodes leading to GW sources.

astro-ph.HE↗