HD 265435 is a binary system with an orbital period of around 100 min that consists of a white dwarf and a hot subdwarf star.
An artist’s impression of HD 265435, a binary system located approximately 1,500 light-years away in the constellation of Gemini. Image credit: Mark Garlick / University of Warwick.
Supernovae of Type Ia are important for cosmology as ‘standard candles.’
Their brightness is constant and of a specific type of light, which means astronomers can compare what luminosity they should be with what we observe on Earth, and from that work out how distant they are with a good degree of accuracy.
By observing these supernovae in distant galaxies, astronomers combine what they know of how fast a galaxy is moving with our distance from the supernova and calculate the expansion of the Universe.
A Type Ia supernova is generally thought to occur when a white dwarf’s core reignites, leading to a thermonuclear explosion.
There are two scenarios where this can happen. In the first scenario, the white dwarf gains enough mass to reach 1.4 times the mass of our Sun, known as the Chandrasekhar limit.
The HD 265435 system fits in the second scenario, in which the total mass of a close binary is near or above this limit.
“We don’t know exactly how these supernovae explode, but we know it has to happen because we see it happening elsewhere in the Universe,” said Dr. Ingrid Pelisoli, an astronomer in the Department of Physics at the University of Warwick and the Institut für Physik und Astronomie at the Universität Potsdam.
“One way is if the white dwarf accretes enough mass from the hot subdwarf, so as the two of them are orbiting each other and getting closer, matter will start to escape the hot subdwarf and fall onto the white dwarf.”
“Another way is that because they are losing energy to gravitational wave emissions, they will get closer until they merge.”
“Once the white dwarf gains enough mass from either method, it will go supernova.”
Dr. Pelisoli and colleagues analyzed the light curve obtained by NASA’s Transiting Exoplanet Survey Satellite (TESS) together with data from Palomar Observatory and the W. M. Keck Observatory to characterize the HD 265435 system and determine the masses of its components.
They found that the hidden white dwarf is as heavy as our Sun, but just slightly smaller than the Earth’s radius.
Combined with the mass of the hot subdwarf, which is a little over 0.6 times the mass of our Sun, both stars have the mass needed to cause a Type Ia supernova.
As the two stars are already close enough to begin spiraling closer together, the white dwarf will inevitably go supernova in around 70 million years.
Theoretical models predict that the hot subdwarf will contract to become a white dwarf star as well before merging with its companion.
“The more we understand how supernovae work, the better we can calibrate our standard candles,” Dr. Pelisoli said.
“This is very important at the moment because there’s a discrepancy between what we get from this kind of standard candle, and what we get through other methods.”
A paper on the findings was published in the journal Nature Astronomy.
_____
I. Pelisoli et al. A hot subdwarf-white dwarf super-Chandrasekhar candidate supernova Ia progenitor. Nat Astron, published online July 12, 2021; doi: 10.1038/s41550-021-01413-0
Article From & Read More ( HD 265435 Will Explode as Type Ia Supernova in 70 Million Years, Astronomers Say | Astronomy - Sci-News.com )https://ift.tt/3icm48z
Science
No comments:
Post a Comment