Lars Bildsten

Modules for Experiments in Stellar Astrophysics (MESA): Time-dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure

The Astrophysical Journal Supplement Series · 2023 · 517 citations

Abstract We update the capabilities of the open-knowledge software instrument Modules for Experiments in Stellar Astrophysics ( MESA ). The new auto _ diff module implements automatic differentiation in MESA , an enabling capability that alleviates the need for hard-coded analytic expressions or finite-difference approximations. We significantly enhance the treatment of the growth and decay of convection in MESA with a new model for time-dependent convection, which is particularly important duri…

PTF10iya: a short-lived, luminous flare from the nuclear region of a star-forming galaxy

Figshare · 2024-01-01 · 58 citations

We present the discovery and characterization of PTF10iya, a short-lived (Δt≈ 10 d, with an optical decay rate of ∼0.3 mag d−1), luminous ( mag) transient source found by the Palomar Transient Factory. The ultraviolet/optical spectral energy distribution is reasonably well fitted by a blackbody with T≈ (1–2) × 104 K and peak bolometric luminosity LBB≈ (1–5) × 1044 erg s−1 (depending on the details of the extinction correction). A comparable amount of energy is radiated in the X-ray band that app…

Shocking and Mass Loss of Compact Donor Stars in Type Ia Supernovae

The Astrophysical Journal · 2024-09-01 · 16 citations

Abstract Type Ia supernovae arise from thermonuclear explosions of white dwarfs accreting from a binary companion. Following the explosion, the surviving donor star leaves at roughly its orbital velocity. The discovery of the runaway helium subdwarf star US 708, and seven hypervelocity stars from Gaia data, all with spatial velocities ≳900 km s −1 , strongly support a scenario in which the donor is a low-mass helium star or a white dwarf. Motivated by these discoveries, we perform three-dimensio…

Morphology and Mach Number Dependence of Subsonic Bondi–Hoyle Accretion

The Astrophysical Journal · 2024-04-29 · 8 citations

Abstract We carry out three-dimensional computations of the accretion rate onto an object (of size R sink and mass m ) as it moves through a uniform medium at a subsonic speed v ∞ . The object is treated as a fully absorbing boundary (e.g., a black hole). In contrast to early conjectures, we show that for an accretor with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>sink</mml:mi> </mml:mrow> </…

Ejecta Wakes from Companion Interaction in Type Ia Supernova Remnants

The Astrophysical Journal · 2025-03-19 · 7 citations

Abstract Type Ia supernovae are triggered by accretion onto a white dwarf from a companion that is most likely Roche lobe–filling at the time of the explosion. The collision between the ejecta and a surviving companion carves out a conical wake, which could manifest as an asymmetry when the ejecta reaches the remnant phase. We simulate the companion interaction using the Athena++ hydrodynamics solver to determine the ejecta structure for a double-degenerate type Ia supernova. Ejecta in the wake…