White Dwarf Rotation as a Function of Mass and a Dichotomy of Mode Line Widths: Kepler Observations of 27 Pulsating DA White Dwarfs through K2 Campaign 8

By J. Hermes, B. Gänsicke, S. Kawaler, S. Greiss, P.-E. Tremblay, N. G. Fusillo, R. Raddi, S. Fanale, K. Bell, E. Dennihy and 8 more. 2017

132 citations recorded by the source corpus.

We present photometry and spectroscopy for 27 pulsating hydrogen-atmosphere white dwarfs (DAVs; a.k.a. ZZ Ceti stars) observed by the Kepler space telescope up to K2 Campaign 8, an extensive compilation of observations with unprecedented duration (>75 days) and duty cycle (>90%). The space-based photometry reveals pulsation properties previously inaccessible to ground-based observations. We observe a sharp dichotomy in oscillation mode line widths at roughly 800 s, such that white dwarf pulsations with periods exceeding 800 s have substantially broader mode line widths, more reminiscent of a damped harmonic oscillator than a heat-driven pulsator. Extended Kepler coverage also permits extensive mode identification: we identify the spherical degree of 87 out of 201 unique radial orders, providing direct constraints of the rotation period for 20 of these 27 DAVs, more than doubling the number of white dwarfs with rotation periods determined via asteroseismology. We also obtain spectroscopy from 4 m-class telescopes for all DAVs with Kepler photometry. Using these homogeneously analyzed spectra, we estimate the overall mass of all 27 DAVs, which allows us to measure white dwarf rotation as a function of mass, constraining the endpoints of angular momentum in low- and intermediate-mass stars. We find that 0.51–0.73 M⊙ white dwarfs, which evolved from 1.7–3.0 M⊙ ZAMS progenitors, have a mean rotation period of 35 hr with a standard deviation of 28 hr, with notable exceptions for higher-mass white dwarfs. Finally, we announce an online repository for our Kepler data and follow-up spectroscopy, which we collect at http://k2wd.org.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/df84f8bf15a64830e466aa3455f33387188205ef

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. J. Fuller
2. Linhao Ma
3. B. Gänsicke
4. A. Piro
5. J. Cummings
6. P.-E. Tremblay
7. Stefan Jordan
8. Thomas R. Marsh

In Instrumentation

1. J. Cummings
2. P.-E. Tremblay
3. Stefan Jordan
4. Thomas R. Marsh
5. Linhao Ma
6. B. Gänsicke
7. S. Toonen
8. J. Fuller

Citations in the corpus

• Slowing the spins of stellar cores (2019, methodology): “Additionally, our models do not take into account binary effects such as mergers (during either stellar evolution or WD mergers) that may produce faster rotating stellar cores and WDs. Kilic et al. (2018) suggest that ∼10 per cent of WDs, especially Figure 7.”
• Most Black Holes Are Born Very Slowly Rotating (2019, background): “Asteroseismic data for low-mass stars (e.g., Deheuvels et al. 2015; Hermes et al. 2017; Gehan et al. 2018) has convincingly demonstrated that the cores of low-mass stars rotate at least an order of magnitude slower than predicted by most prior stellar models (Cantiello et al. 2014).”
• AGaiaData Release 2 catalogue of white dwarfs and a comparison with SDSS (2018, background): “…relation, e.g., Weidemann 1977; Dobbie et al. 2006b; Williams et al. 2009; Kalirai et al. 2014; Romero et al. 2015; Cummings et al. 2016), internal rotation profiles and loss of angular momentum (Charpinet et al. 2009; Hermes et al. 2017), and fundamental nuclear reaction rates (Kunz et al. 2002).”