Sep 09, 2014
David Kaplan, University of Wisconsin, Milwaukee
"Helium-Core White Dwarfs Three Ways"
New observations have discovered increasing numbers of extremely
low-mass helium-core white dwarfs in compact binary systems that will
merge within a Hubble time. These white dwarfs differ from more
common carbon/oxygen systems by the presence of a thick envelope
supported by stably burning hydrogen, which can keep the star hot and
visible for Gyr. These envelopes can dramatically alter the
appearances of the stars and the eventual fates of the binary systems.
We discuss three recent discoveries of helium-core white dwarfs: the
first detatched eclipsing double-white dwarf system, a strange
metal-rich low-gravity companion to a massive millisecond pulsar, and
a millisecond pulsar in a stellar triple system. Each of these gives
unique insight into the structure, properties, and evolution of white
dwarfs and compact binaries, and in some cases the nature of gravity
itself. Finally, we will discuss a recent CO white dwarf companion to
a millisecond pulsar that may be the coolest white dwarf known.