Massive Outburst Observed in Pulsating White Dwarf GD 1212
Astronomers using NASA's Kepler space telescope observed a dramatic brightening event lasting roughly half a day in the pulsating white dwarf GD 1212, with the star becoming up to 17.5% brighter due to a temperature increase of approximately 850 Kelvin. The outburst is believed to result from nonlinear mode coupling via parametric instability, where energy from excited pulsation modes is rapidly transferred to damped modes that dissipate near the surface. This observation provides rare high-resolution data on how pulsations behave during extreme temperature changes, offering insights into the physics of white dwarf oscillations.
Researchers analyzing data from NASA's K2 mission (an extended phase of the Kepler Space Telescope) detected a large brightening event in the hydrogen-atmosphere white dwarf GD 1212 that lasted approximately half a day during Campaign 12 observations. The star exhibited a rich spectrum of long-period pulsations (~1100 seconds) over 80 days of observation, with rapid variations in frequency and amplitude, but only one major outburst occurred. The outburst caused the entire white dwarf to brighten by up to 17.5%, corresponding to an effective temperature increase of roughly 850 Kelvin, while pulsational variability during the event showed shorter periods and higher amplitudes. The researchers refined mode identification and identified a sequence of dipole and quadrupole splittings indicating an overall rotation rate of approximately 17.0 hours. The outburst is attributed to parametric instability, a nonlinear process where energy stored in linearly excited parent modes is rapidly transferred to damped child modes that dissipate near the surface. GD 1212 is now the eighth known pulsating hydrogen-atmosphere DAV white dwarf to exhibit outburst behavior, but it displayed the largest outburst yet recorded and has the longest inferred recurrence timescale.
What's missing
The study does not discuss the physical mechanisms that trigger the transition from stable pulsations to parametric instability, nor does it address why GD 1212's outburst recurrence timescale is longer than other known DAV white dwarfs with similar behavior. The paper also does not provide predictions for when the next outburst might occur.
What different sources said
- arXiv astro-phCenter
Mode Instability and a Massive, Isolated Outburst in the Pulsating White Dwarf GD 1212
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