Binary systems have received much attention as possible progenitors of Type Ia supernovae, but long-term gravitational effects in tight triple or quadruple systems could also play a key role in producing stellar explosion of this type. In new research, a team of astronomers from Europe and New Zealand studied properties of HD 74438, a 2+2 hierarchical stellar system within the open star cluster IC 2391.
HD 74438 is located approximately 476 light-years away in the constellation of Vela.
This system belongs to one of the closest young clusters, IC 2391, containing 254 member stars.
“HD 74438 is the youngest — only 43-million years old – spectroscopic quadruple discovered in the Milky Way Galaxy to date, and among the quadruple systems with the shortest outer orbital period (six years),” said Dr. Thibault Merle from the Institut d’Astronomie et d’Astrophysique at the Université Libre de Bruxelles and colleagues.
HD 74438 was discovered in 2017 by astronomers using data from the Gaia-ESO Survey.
Follow-up observations of the system using high-resolution spectrographs at the University of Canterbury Mt John Observatory and the Southern African Large Telescope were obtained over several years to precisely track the orbits of the stars.
The astronomers determined that HD 74438 is made up of four gravitationally bound stars: a short-period binary system orbiting another short-period binary on a longer orbital period (2+2 configuration).
They also found that the gravitational effects of the outer binary is changing the orbits of the inner binary, causing it to become more eccentric.
State-of-the art simulations of this system’s future evolution show that such gravitational dynamics can lead to one or multiple collisions and merger events producing white dwarfs with masses just below the Chandrasekhar limit.
As a result of mass transfer or mergers, these white dwarfs can produce Type Ia supernova explosions, also known as thermonuclear supernovae.
“A star like our Sun will end its life as a small dense dead star known as a white dwarf, and the mass of white dwarfs cannot go above the so-called Chandrasekhar limit (about 1.4 times the mass of the Sun),” said Dr. Karen Pollard, an astronomer in the School of Physical and Chemical Sciences at the University of Canterbury.
“If it does, because of mass transfer or merger events, it can collapse and produce a thermonuclear supernova.”
“Interestingly, 70% to 85% of all thermonuclear supernovae are now suspected to result from the explosion of white dwarfs with sub-Chandrasekhar masses.”
“As a result of mass transfer or mergers, these white dwarf stars can explode as a thermonuclear supernova explosion.”
“The evolution of stellar quadruples such as HD 74438 thus represents a new promising channel to form thermonuclear supernova explosions in the Universe,” she said.
The team’s paper appears in the journal Nature Astronomy.
T. Merle et al. A spectroscopic quadruple as a possible progenitor of sub-Chandrasekhar type Ia supernovae. Nat Astron, published online May 12, 2022; doi: 10.1038/s41550-022-01664-5
Source link: https://www.sci.news/astronomy/type-ia-supernovae-quadruple-systems-10812.html