Binary White Dwarfs in the Supernova Ia Progenitor Survey

Napiwotzki, R.; Karl, C.; Nelemans, G.; Yungelson, L.; Christlieb, N.; Drechsel, H.; Heber, U.; Homeier, D.; Koester, D.; Leibundgut, B.; Marsh, T.R.; Moehler, S.; Renzini, A.; Reimers, D.

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Author

Napiwotzki, R.

Karl, C.

Nelemans, G.

Yungelson, L.

Christlieb, N.

Drechsel, H.

Heber, U.

Homeier, D.

Koester, D.

Leibundgut, B.

Marsh, T.R.

Moehler, S.

Renzini, A.

Reimers, D.

Abstract

We report results of a systematic radial velocity survey for double degenerate (DD) binaries as potential progenitors of type Ia supernovae: SPY (ESO Supernovae Ia Progenitor surveY). More than 1000 white dwarfs (WDs) and pre-white dwarfs were observed with the VLT. The aim of SPY is to perform a statistically significant test of the DD scenario. We give an overview of the project and follow-up results. The sample is used for two tests of the contempo- rary picture of close binary evolution leading to DDs. It is shown that the SPY observations of low mass He-core WDs (HeWDs) are inconsistent with the idea that they all reside in close binary systems. We carry out a model atmosphere analysis of WDs residing in double-lined binaries and estimate individual cooling ages. For a number of systems the younger (and hotter) component is the less massive one, as expected. However, for some systems the mass ratio is inverted.