The mass and temperature distribution of accreting white dwarf
A large HST/COS program

2011 was an extraordinary year for astronomy, with the Nobel Prize for Physics being awarded for the discovery of dark enery. While most astronomers agree that type Ia supernovae (SNIa) arise from white dwarfs exploding in some kind of binary system, we are still unable to explain the precise nature of SNIa progenitors, the very tool that led to the discovery of dark energy. One way to  improve our understanding of the evolution of compact binaries and the effect that the accretion of mass and angular momentum has on the structure of white dwarfs is to study cataclysmic variables (CVs). As simple as this idea seems, it can only be done in the ultraviolet, as the white dwarfs in CVs are outshone in the optical by light from the accretion disk and / or the donor star.

We are carrying out a large program with the Hubble Space Telescope to obtain ultraviolet spectroscopy of more than 40 cataclysmic variables, with the aim to measure the temperatures, rotation rates, atmosphere abundances, and ultimately the masses of their accreting white dwarfs. The observations are scheduled to start in October 2012, and will run through until March 2014.

Because of the extremely variable nature of CVs, we have to make absolutely sure that the HST observations are obtained during quiescence, as the detectors of the Cosmic Origin Spectrograph can be damaged by exposure to too much light.

Therefore the success of this project entirely relies on ground-based observers who can monitor the targets in the weeks prior to the HST observations.

The full list of targets is available as HTML (including links to finding charts, SDSS data,  the AAVSO AUIDs/VSX entries, and the light curve over the last 50 days),  Excel spreadsheet and PDF, and more detailed information of the targets can be found here.

The current "plan windows", i.e. when HST could observe the targets, are given here.

For any additional information, please contact Boris Gaensicke

Next HST observations:

None ... we are done!