Theron ejects white dwarfs from thermonuclear supernova binary system

A white dwarf star named SDSS J124043.01 + 671034.68 (SDSS J1240 + 6710) is traveling 900,000 km / h (559,234 mph) through our Milky Way Galaxy. It is also a particularly low mass for a white dwarf – only 40% of our sun’s mass – which would correspond to mass loss from a fractional supernova. According to new research, the SDSS J1240 + 6710 was a member of a binary system that survived the so-called thermonuclear supernova event, which sent it and its partner flying from the Milky Way in opposite directions.

An artist’s impression of a thermonuclear supernova: the material emitted by the supernova will initially expand very rapidly, but then slowly slow down, creating a complex giant bubble of hot flaring gas; Finally, the eruption remnant of the white dwarf that will overtake these gaseous layers, and accelerate their journey across our Milky Way Galaxy. Image Credit: Mark Garlick / University of Warwick.

After these giant stars die and shed their outer layers, the cool dwarfs are the remains of red corpses over the course of billions of years.

The majority of white dwarfs have an atmosphere composed almost entirely of hydrogen or helium, with occasional evidence of carbon or oxygen being separated from the star’s core.

The SDSS J1240 + 6710, which was discovered in 2015, is 1,432 light-years away from us in the constellation of Draco.

Also known as WD 1238 + 674 and LSPM J1240 + 6710, the star was first found in oxygen-dominated environments with significant traces of neon, magnesium, and silicon.

Professor Boris Gensike of the University of Warwick said, “This star is unique because it has all the salient features of a white dwarf, but has very high velocity and unusual abundance, which makes no sense when combined with low mass” studies.

Using the onboard cosmic origin spectrograph at NASA / ESA Hubble Space Telescope, Professor Gansike and his colleagues identified carbon, sodium, and aluminum in the atmosphere of the SDSS J1240 + 6710, which all occur in the first thermonuclear reactions of a supernova .

However, there is an apparent lack of elements, known as ‘iron groups’, of iron, nickel, chromium and manganese.

These heavier elements are typically cooked with lighter, and form the defining characteristics of thermonuclear supernovae.

The lack of iron group elements in SDSSJ1240 + 6710 suggests that the star underwent only a partial supernova before the nuclear explosion.

“The white dwarf has a chemical structure that is a fingerprint of atomic burns, low mass, and very high velocity: all these facts mean that it must have come from some kind of close binary system and must have a thermonuclear nucleon.” Professor Gensike said.

“It must have been a type of supernova, but one of a kind we had not seen before.”

The authors state that the supernova disrupted the orbit of the white dwarf with its companion star when it abruptly fired a large portion of its mass.

Both stars must have been moving in opposite directions in their orbital velocity in a sort of slingshot maneuver. This will account for the high velocity of the star.

“If it was a tight binary and it went through a thermonuclear ignition, greatly expanding its mass, you would have conditions producing low-mass white dwarfs and it flew with its orbital velocity,” Professor Lenske he said.

The best-studied thermonuclear supernovae are Type Ia. But there is increasing evidence that thermonuclear supernovae can occur under very different circumstances.

SDSSJ1240 + 6710 may have survived a type of supernova that has not yet been caught in the act.

Without the radioactive nickel of the long-lasting power of the Type I supernova, the explosions that send SDSS1240 + 6710 into our Galaxy would have been a brief flash of light that would have been difficult to detect.

“Gonomic stated that the study of thermonuclear supernovae is a very large field and a major attempt to find supernovas in other galaxies.”

“The difficulty is that you see the star when it bursts but it is very difficult to know the properties of the star before it explodes.”

“The fact that such a low-mass white dwarf went through carbon burns is a testament to the impact of binary evolution and its effect on the chemical evolution of the universe,” senior author Professor SO Kepler, an astronomer at Universidad Federal it is said. Rio Grande do Sul.

“Once again, the synergy between very precise Gaia astrometry and spectroscopic analysis has helped to inhibit the striking properties of a unique white dwarf, possibly formed in a thermonuclear supernova and at full velocity as the result of an explosion. Is thrown out “. Author Dr. Roberto Reddy, an astronomer at the Universitat Politecica de Catalunya.

Team paper was published Monthly notice of the Royal Astronomical Society.


Boris T. Gensike and others. 2020. SDSS J124043.01 + 671034.68: Partially burned remains of a low-mass white dwarf that had undergone thermonuclear ignition? Mnras 496 (4): 4079–4086; doi: 10.1093 / mnras / staa1761

This article is based on a press release provided by the University of Warwick.