The imprint of convection on Type I X-ray bursts: Pauses in photospheric radius expansion lightcurves
arXiv:2301.08769 · doi:10.3847/1538-4357/ace43c
Abstract
Motivated by the recent observation by NICER of a type I X-ray burst from SAX J1808.4-3658 with a distinct "pause" feature during its rise (Bult et al. 2019), we show that bursts which ignite in a helium layer underneath a hydrogen-rich shell naturally give rise to such pauses, as long as enough energy is produced to eject the outer layers of the envelope by super-Eddington winds. The length of the pause is determined by the extent of the convection generated after ignition, while the rate of change of luminosity following the pause is set by the hydrogen gradient left behind by convection. Using the MESA stellar evolution code, we simulate the accumulation, nuclear burning and convective mixing prior to and throughout the ignition of the burst, followed by the hydrodynamic wind. We show that the results are sensitive to the treatment of convection adopted within the code. In particular, the efficiency of mixing at the H/He interface plays a key role in determining the shape of the lightcurve. The data from SAX J1808.4-3658 favors strong mixing scenarios. Multidimensional simulations will be needed to properly model the interaction between convection and nuclear burning during these bursts, which will then enable a new way to use X-ray burst lightcurves to study neutron star surfaces.
arXiv comment13 pages, 7 figures. Published in ApJ (August 2023)
References in corpus (32)
- SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
- Array Programming with NumPy
- Modules for Experiments in Stellar Astrophysics (MESA)
- Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
- Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
- Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
- Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
- Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
- The Dense Matter Equation of State from Neutron Star Radius and Mass Measurements
- Models for Type I X-Ray Bursts with Improved Nuclear Physics
- Convective-reactive proton-C12 combustion in Sakurai's object (V4334 Sagittarii) and implications for the evolution and yields from the first generations of stars
- Zero-metallicity stars I. Evolution at constant mass
- Exposing the Nuclear Burning Ashes of Radius Expansion Type I X-ray Bursts
- Helium-rich thermonuclear bursts and the distance to the accretion-powered millisecond pulsar SAX J1808.4-3658
- Thermonuclear X-ray bursts
- Nuclear heating and melted layers in the inner crust of an accreting neutron star
- On the proper use of the Schwarzschild and Ledoux criteria in stellar evolution computations
- Eddington-limited X-ray Bursts as Distance Indicators. II. Possible Compositional Effects in Bursts from 4U 1636-536
- A NICER thermonuclear burst from the millisecond X-ray pulsar SAX J1808.4-3658
- Consistent Modeling of GS 1826-24 X-ray Bursts for Multiple Accretion Rates Demonstrates the Possibility to Constrain rp-process Reaction Rates
- Convective H-He Interactions in Massive Population III Stellar Evolution Models
- Thermonuclear burst observations for model comparisons: a reference sample
- Convective boundary mixing in a post-He core burning massive star model
- NICER Detection of Strong Photospheric Expansion during a Thermonuclear X-Ray Burst from 4U 1820-30
- A Bayesian Approach to Matching Thermonuclear X-ray Burst Observations with Models
- Multidimensional Modeling of Type I X-ray Bursts. II. Two-Dimensional Convection in a Mixed H/He Accretor
- Schwarzschild and Ledoux are equivalent on evolutionary timescales
- NICER Discovers Spectral Lines During Photospheric Radius Expansion Bursts from 4U 1820-30: Evidence for Burst-driven Winds
- 3D1D hydro-nucleosynthesis simulations. I. Advective-reactive post-processing method and its application to H ingestion into He-shell flash convection in rapidly accreting white dwarfs
- Super-Eddington winds from Type I X-ray bursts
- Evidence for the photoionization absorption edge in a photospheric radius expansion X-ray burst from GRS 1747312 in Terzan 6
- Expanded atmospheres and winds in Type I X-ray bursts from accreting neutron stars