Update on extensions to the Texas interface

Clemens, Jan

doi:10.1515/astro-1993-3-422

Cited by 4 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The most common way to visualize the increasing mode periods as DAVs cool is to compute the weighted mean period (WMP) of the significant pulsations (Clemens 1993). The WMP is linearly weighted by the amplitude of each mode, such that WMP = i P i A i / i A i , where P i and A i are the period and amplitude, respectively, of each significant independent pulsation detected (excluding nonlinear combination frequencies).…”

Section: Characteristics Of the Dav Instability Stripmentioning

confidence: 99%

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

Hermes

Gänsicke

Kawaler

et al. 2017

ApJS

190

226

View full text Add to dashboard Cite

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 linewidths at roughly 800 s, such that white dwarf pulsations with periods exceeding 800 s have substantially broader mode linewidths, 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 61 out of 154 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 4m-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 − 3.0M ⊙ 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 k2wd.org.

show abstract

Section: Characteristics Of the Dav Instability Stripmentioning

confidence: 99%

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

Hermes

Gänsicke

Kawaler

et al. 2017

ApJS

190

226

View full text Add to dashboard Cite

show abstract

“…If the driving periods resonate with an available mechanical oscillation mode of the star, this mode may grow to a large enough amplitude to become observable. This formula immediately tells us that as the star cools, the oscillation periods become longer, which is observed for DAVs (Clemens 1993). Table 1 shows which stellar parameters we can get from observations of white dwarfs (Bradley 1993) …”

Section: What Can We Learn From White Dwarf Pulsations?mentioning

confidence: 84%

Near Continuous Photometry with the Whole Earth Telescope (WET)

Solheim

2003

Open Astronomy

View full text Add to dashboard Cite

Abstract. The Whole Earth Telescope (WET) saw first light in 1988.It was invented by scientists from the Astronomy Department, University of Texas at Austin. The idea was to generate a world-wide network of cooperating astronomical observatories to obtain uninterrupted time-series measurements of some variable stars. The technological goal was to resolve the multi-periodic oscillations in these objects into their individual components; the scientific goal was to construct accurate theoretical models of the target objects, constrained by their observed behavior, from which fundamental astrophysical parameters could be derived. This approach has been extremely successful, and has placed stellar seismology at the forefront of stellar astrophysics. The network is run as a single astronomical instrument with many operators, and the collaboration includes scientists from all continents on our planet, taking part in the observations, data reduction, analysis and theoretical interpretation. The expertise of Lithuanian astronomers in photometry, and their access to the observing station Mt. Maidanak in Uzbekistan, has been important for the success of the network.

show abstract

“…For example, the power with a period near 118 s definitely has two components, and a comparison of the spacing between these components with the frequency spacing of the 143 s components strongly suggests, on theoretical grounds, that the latter frequency results from an I = 2 g-mode pulsation of the white dwarf (Bradley 1993, Clemens 1993. The dominant 192 s oscillation is clearly evident in even short data segments, but even the DFT of the combined WET data segment does not clearly reveal the rotational splitting of this mode.…”

Section: Preliminary Resultsmentioning

confidence: 99%