The ELM Survey. V. Merging Massive White Dwarf Binaries

TL;DR

This paper reports the discovery of 17 low-mass white dwarf binaries, including systems with potential to evolve into supernovae or millisecond pulsar binaries, significantly expanding the known population of such systems.

Contribution

It presents new discoveries of 17 low-mass white dwarf binaries, including four with double degenerate companions and potential for diverse evolutionary outcomes, enhancing the ELM Survey dataset.

Findings

17 new low-mass white dwarf binaries discovered

Six binaries will merge within 10 Gyr

Four systems have massive companions potentially leading to supernovae or pulsars

Abstract

We present the discovery of 17 low mass white dwarfs (WDs) in short-period P<1 day binaries. Our sample includes four objects with remarkable log(g)~5 surface gravities and orbital solutions that require them to be double degenerate binaries. All of the lowest surface gravity WDs have metal lines in their spectra implying long gravitational settling times or on-going accretion. Notably, six of the WDs in our sample have binary merger times <10 Gyr. Four have >=0.9 Msun companions. If the companions are massive WDs, these four binaries will evolve into stable mass transfer AM CVn systems and possibly explode as underluminous supernovae. If the companions are neutron stars, then these may be milli-second pulsar binaries. These discoveries increase the number of detached, double degenerate binaries in the ELM Survey to 54; 31 of these binaries will merge within a Hubble time.