Conveners
Observed WD Populations 2: Observed populations
- Valeriya Korol (Leiden Observatory)
Observed WD Populations 2: Triples
- Hagai Perets (Technion - Israel institute of technology)
The white dwarf luminosity function is an essential tool to understand the nature and the history of the different components of our Galaxy. However, observational white dwarf samples from which the luminosity functions are built are contaminated by unresolved double-degenerates. These systems are considered as 'single' white dwarfs from an observational point of view and therefore contribute...
About 10% of white dwarfs in the solar neighborhood are strongly magnetic, with field strengths of up to 1000 MG. Curiously, high field magnetic white dwarfs are never found in wide binary systems with late-type stellar companions. This suggests that merging binaries within a common envelope may be required to explain the incidence of magnetism in these objects. However, there are also several...
There are several indications that stellar mergers are common outcomes of binary evolution. Mergers involving white dwarfs are linked to several classes of transients, such as supernova type, and may leave imprints in other observables as well, e.g. the WD mass distribution. The alleged excess of WDs with masses around 0.8solar masses has been linked to double white dwarf mergers. Here we...
Recently, Gaia DR2 has revealed an enhancement of high-mass WDs on the H-R diagram, called the Q branch. The distribution of photometric ages and velocities of WDs around the branch suggest an extra cooling delay beyond current WD cooling models. To explore the properties of this delay, we statistically compare two age indicators -- the dynamical age reflected by transverse velocity and the...
The collisional-triple SN Ia progenitor model posits that SNe Ia result from head-on collisions of binary white dwarfs (WDs), driven by dynamical perturbations by the tertiary stars in mild-hierarchical triple systems. To reproduce the Galactic SN Ia rate, some 30-55 per cent of all WDs would need to be in triple systems of a specific architecture. We test this scenario by searching the Gaia...
Despite the importance today of Type Ia supernova explosions (SNe Ia) for a number of branches of astrophysics and cosmology, their progenitors and exact explosion mechanism remain unclear. The two standard scenarios for SNe Ia explosions, single-degenerate accretion and double-degenerate mergers, both have a number of theoretical and observational challenges, and there is still no consensus...
