Unraveling the oscillations of the richest pulsating hydrogen-atmosphere white dwarf
Abstract
Most stars in our Galaxy will end or have already ended their lives as white dwarf stars, making them important benchmarks for stellar evolution. Here we propose to obtain COS far-ultraviolet spectroscopy of a pulsating hydrogen-atmosphere white dwarf (DAV) with extensive, space-based photometry obtained by the Kepler spacecraft during the K2 mission. The pulsation spectrum is the richest of any DAV collected to date, but to extract any information about the white dwarf interior we must identify the spherical degree (l) of the modes present. Our time-tagged ultraviolet observations will enable us to identify the spherical degree of the highest-amplitude pulsation modes, since the ratios of the ultraviolet-to-optical pulsation amplitudes strongly depend on the geometry of the pulsation modes. This will decisively determine if most of the modes present are a series of l=3 modes, as it appears from the frequency multiplets in the K2 data; however, l=3 modes have never been clearly identified in a pulsating white dwarf. Our far-ultraviolet spectroscopy, covering the H2/H2+ quasi-molecular satellites around 1400 and 1600 AA, will also measure the white dwarf temperature and mass to an accuracy unachievable from the ground. This robust temperature and mass will anchor our detailed asteroseismic investigation of this stellar remnant. The unique combination of HST and Kepler observations will make this white dwarf a benchmark for the unprecedented opportunities for white dwarf archaeology enabled by the original Kepler mission and its extension into the ecliptic, K2.
- Publication:
-
HST Proposal
- Pub Date:
- June 2016
- Bibcode:
- 2016hst..prop14691H