New types of stars aren’t found very often but last year, Patrick Dufour and pals discovered several white dwarfs with carbon atmospheres. Before then white dwarfs were thought to come in two flavours: with atmopsheres dominated by either hydrogen or helium. Astronomers suddenly had a new toy to play with.
Dufour found nine examples of his carbon dwarfs in the data regurgitated by the Sloan Digital Sky Survey and more are likely to be found as the skies continue to be searched.
So what are white dwarfs with carbon atmospheres like? Dufour and some theorists have been working out the details and today publish their results. Carbon dwarfs should be great throbbing balls of fire. Yep, pulsating stars.
They’ve had a bit of luck here. Turns out that Gilles Fontaine at the University of Montreal produced a theoretical study of carbon-based white dwarfs for his phd thesis 35 years ago, long before they were even discovered.
A quick look through his notes has revealed that these stars should pulsate as carbon is cycled through the atmosphere by convection (although the exact details depend on the amount of carbon in the stellar atmosphere).
Now the hunt is on to find more of these rare white dwars and to measure the amount of light they produce. “We are eagerly awaiting the results,” say Fontaine and Dufour.
Ref: arxiv.org/abs/0803.2255: Might Carbon-Atmosphere White Dwarfs Harbour a New Type of Pulsating Star?
Having eagerly waited all of one day, Dufour and a few buddies have announced the discovery of a pulsating carbon-rich white dwarf.
Congratualtions to them but there is a potential fly in the ointment: what looks like a pulsating dwarf could actually be a binary system of two white dwarfs. Dufour is unfazed. He points out that the characteristics of the system are unique so either way, they’ve found a new class of something or other.
He finishes with this: “We will continue the search for other objects of this exciting and enigmatic class.”
The world expects!
Ref: arxiv.org/abs/0803.2646: SDSS J142625.71+575218.3, a Prototype for a New Class of Variable White Dwarf