Conveners
Mergers: Numerical Modeling
- Silvia Toonen (University of Birmingham)
Mergers: Observational Evidence
- Tom Marsh (University of Warwick)
The merger of carbon-oxygen or oxygen-neon white dwarfs need not lead to a thermonuclear explosion, even when their total mass is in excess of the Chandrasekhar mass. I will discuss the post-merger evolution of these massive merger remnants, which may sometimes result in the production of a neutron star, and draw parallels to ultra-stripped core collapse supernovae. I will also describe the...
The final outcome of white dwarf mergers across the entire merger parameter space is still relatively uncertain. This is mainly because, as the evolutionary phases involved span several orders of magnitude in timescales, one needs different numerical approaches/codes such as smoothed-particle hydrodynamics (SPH), magnetohydrodynamics (MHD), and detailed stellar evolution for the dynamical...
We present the results of an investigation of the dredge-up and mixing during the merger of two white dwarfs (WDs) with different chemical compositions by conducting hydrodynamic simulations of binary mergers for three representative mass ratios. In all the simulations, the total mass of the two WDs is $≲1.0 {\mathrm M_☉}$. Mergers involving a CO and a He WD have been suggested as a possible...
The R Coronae Borealis (RCB) stars are rare hydrogen-deficient, carbon-rich supergiants. They undergo extreme, irregular declines in brightness of many magnitudes due to the formation of thick clouds of carbon dust. Two scenarios have been proposed for the origin of an RCB star: the merger of a CO/He white dwarf (WD) binary and a final helium-shell flash. We constructed post-merger spherical...
The merger of two white dwarfs with a combined mass below the Chandrasekhar-limit is expected to be non-explosive, resulting in a single massive white dwarf. However, because single star evolution can also produce massive white dwarfs, few known degenerate stars have categorically been confirmed as merger products.
We report the identification of a 1.15 $M_\odot$ white dwarf with a unique...
We propose a new category of low frequency gravitational wave sources
related to mergers of double white dwarfs. A remnant just after a merger
is a rapidly and differentially rotating objects, which may develop
non-axisymmetric instability of hydrodynamical origin. If the remnant
is susceptible to the so-called 'low T/W' instability, m=2 (bar)
or m=1 (spiral) density pattern may develop (here...
