W H A T
Compact White Dwarf Binaries Conference
W H E N
September 15 -21, 2019
Compact white dwarf binaries are formed when the more massive component in a stellar binary expands towards the end of its stellar life and engulfs its companion. This brief and dynamically violent common envelope phase shrinks the orbital separation, and results in a radically different evolution compared to single star evolution. Compact white dwarf binaries become interactive and lead to a variety of astrophysical important outcomes, including supernovae type Ia and low-frequency gravitational wave sources.
The goal of this conference is to bring together experts working across all areas related to compact white dwarf binaries, and to address the following key questions:
(1) What is the efficiency of common envelope evolution in extracting energy and angular momentum from binaries?
This phase is of fundamental importance to all compact binaries, including stellar mass black hole binaries and milli-second pulsars.
(2) What mechanisms drive the long-term evolution of compact binaries?
Magnetic wind braking plays an important role, but is so far still poorly understood, and different parameterisations span orders of magnitude in efficiency.
(3) Under what circumstances do white dwarfs grow in mass?
Supernovae type Ia (SN Ia) are the gold standard cosmic distance beacons, yet we now know that there is diversity among the observational properties of SN Ia, which is probably linked to multiple underlying populations of progenitor systems.
(4) How does accretion disc dynamics vary over the relevant parameters space, disc size and accretion rate?
Accretion discs are extremely important structures in many contexts, from star formation to AGN, yet the discs in cataclysmic variables are best suited for observational studies both in terms of time scales and the ability to image their sub-structures via Doppler tomography.
(5) How does the presence of strong magnetic fields affect accretion physics?
While neutron stars have higher surface fields, accreting white dwarfs have won in terms of magnetic moment, and the discovery of the first white-dwarf radio pulsar in 2016 demonstrates that we are still in an exploratory phase of this area of physics.
(6) What are the properties of the Galactic population of ultracompact binaries, and what evolutionary paths produce them?
Ultracompact white dwarf binaries are among the shortest binaries know, with periods down to a few minutes. They are expected to be among the strongest low-frequency gravitational wave signals, and a proper understanding of their population is very timely.
(7) The field of cataclysmic variables and related objects has seen transformational progress over the past decade, driven by new powerful instrumentation and large photometric time-domain and spectroscopic surveys.
We now know several thousand cataclysmic variables and post common envelope binaries, spanning a very wide range in stellar and binary parameters. New state-of-the-art facilities are providing multi-wavelength information on their spectral properties and variability, and Gaia will have the largest impact by delivering accurate distances for the first time. Within a few years, we will be able to derive accurate space densities, luminosities, and accretion rates, essential ingredients to revolutionize our understanding of the evolutionary paths of compact binaries in general.
Boris Gaensicke, Gagik Tovmassian
Dean Townsley, Ken Shen,
Matthias Schreiber, Silvia Toonen,
Martin Henze, Laura Chomiuk,
Christian Knigge, Simone Scaringi,
Juan Hernández Santisteban,
Pablo Rodríguez-Gil, Brent Miszalski,
Federico Bernardini, Axel Schwope
Yerevan State University