UTexas: Dying Stars Suffer from "Irregular Heartbeats"

[bystander]

Dying Stars Suffer from "Irregular Heartbeats"
University of Texas | McDonald Observatory | 26 Aug 2015

Some dying stars suffer from ‘irregular heartbeats,’ research led by astronomers at The University of Texas at Austin and the University of Warwick has discovered.

The team discovered rapid brightening events — outbursts — in two otherwise normal pulsating white dwarf stars. Ninety-seven percent of all stars, including the Sun, will end their lives as extremely dense white dwarfs after they exhaust their nuclear fuel. Such outbursts have never been seen in this type of star before.

“It’s the discovery of an entirely new phenomenon,” said graduate student Keaton Bell of The University of Texas at Austin. Bell reported the first pulsating white dwarf to show these outbursts, KIC 4552982, in a recent issue of The Astrophysical Journal.

This week, a team led by recent University of Texas PhD J.J. Hermes, now of the University of Warwick, is reporting the second white dwarf to show this trait: PG1149+057. Hermes’ team includes Bell and others from The University of Texas. Their research is published in the current Astrophysical Journal Letters.

Both white dwarf discoveries were made using data from the Kepler space mission. The Kepler spacecraft trails Earth in its orbit around the Sun, recording time lapse movies of a few patches of sky for months on end.

The Kepler data show that in addition to the regular rhythm of pulsations expected from a white dwarf, which cause the star to get a few percent brighter and fainter every few minutes, both stars also experienced arrhythmic, massive outbursts every few days, breaking their regular pulse and significantly heating up their surfaces for many hours. ...

Dying Star Suffers "Irregular Heartbeats"
University of Warwick | 2015 Aug 26

KIC 4552982: Outbursts and Asteroseismology from the Longest Pseudo-Continuous Light Curve of a ZZ Ceti - Keaton J. Bell et al

• Astrophysical Journal 809(1):14 (2015 Aug 10) DOI: 10.1088/0004-637X/809/1/14
  arXiv.org > astro-ph > arXiv:1506.07878 > 25 Jun 2015

A second case of outbursts in a pulsating white dwarf observed by Kepler - J. J. Hermes et al

• Astrophysical Journal Letters 810(1):L5 (2015 Sep 01) DOI: 10.1088/2041-8205/810/1/L5
  arXiv.org > astro-ph > arXiv:1507.06319 > 22 Jul 2015

[Ann]

Dying stars? I thought white dwarfs were actually dead stars, where all energy production had ceased apart from thermal radiation from their blisteringly hot but cooling surfaces.

Ann