The quickest optical flash of a Type Ia supernova has been detected, according to a study published in the Astrophysical Journal Letters on December 8, 2021.
Many celebrities’ lives end in a dramatic explosion. The majority of big stars will erupt as supernovae.
Even though a white dwarf star is the remnant of an intermediate mass star like our Sun, it has the potential to explode if it is part of a close binary star system, in which two stars orbit each other. Type Ia supernovae are the most common type of supernovae.
Researchers utilize Type Ia supernovas as a standard candle for distance measurements in astronomy because of their uniform and extraordinarily high brightness, which is around 5 billion times brighter than our Sun. Type Ia supernovae, being the most effective example, assisted researchers in discovering the accelerated expansion of our universe.
Despite the Type Ia supernova cosmology’s enormous success, basic questions like as what the progenitor systems of Type Ia supernovae are and how Type Ia supernova explosions are ignited remain unanswered.
To solve these long-standing problems, a team of astronomers led by Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher Ji-an Jiang used new-generation wide-field survey facilities, including the Tomo-e Gozen camera, the world’s first wide-field mosaic CMOS sensor imager, to try to catch Type Ia supernovae within one day of their explosions, dubbed early-phase Type Ia supernovae
One transient, Tomo-e202004aaelb, caught Jiang’s eye when he checked early-phase supernova candidates uncovered by the Tomo-e transient survey on a regular basis.
“Tomo-e202004aaelb was discovered with high brightness on April 21 in 2020. Surprisingly, its brightness showed significant variation in the next two days and then behaved like a normal early-phase Type Ia supernova. We have discovered several early-phase Type Ia supernovae that show interesting excess emission in the first few days of their explosions but have never seen such a fast and prominent early emission in optical wavelengths. Thanks to the high-cadence survey mode and the excellent performance of Tomo-e Gozen, we can perfectly catch this amazing feature for the first time. Such a prompt early flash should originate from a different origin compared to previously dis covered early-excess Type Ia supernovae,” said Jiang.
At the first look of the spectrum taken just after the initial flash, it stood out as something different from normal supernovae. We noticed that a brightest class of Type Ia supernovae might look like this one if they would be observed in such an early phase. Our classification was subsequently confirmed as the spectra evolve to look more and more similar to the previously found bright Type Ia supernovae.
Miho Kawabata
The origin of the mysterious fast optical flash can be explained by the energy released from an interaction between supernova ejecta and a dense and confined circumstellar material (CSM) soon after the supernova explosion, according to computational simulations by Kyoto University Associate Professor Keiichi Maeda.
“We have not seen such a short and bright flash from Type Ia supernovae before, even with a recently increasing number of very early discoveries soon after the supernova explosion in the last few years, including those discovered by our team. The nature of the CSM must reflect the nature of the progenitor star, and thus this is a key to understanding what kind of a star explodes and how they do so. A question is what makes this supernova so special,” said Maeda.
The scientists discovered that the SN is a variant of brightest Type Ia supernovae after spectroscopic measurements with Kyoto University’s Seimei telescope.
“At the first look of the spectrum taken just after the initial flash, it stood out as something different from normal supernovae. We noticed that a brightest class of Type Ia supernovae might look like this one if they would be observed in such an early phase. Our classification was subsequently confirmed as the spectra evolve to look more and more similar to the previously found bright Type Ia supernovae,” said Kyoto University Project Researcher Miho Kawabata.
The team’s findings suggest that at least a fraction of Type Ia supernovae are born in a dense CSM environment, putting a tight limit on the progenitor system of these magnificent cosmic events.
Because Tomo-e202004aaelb (SN 2020hvf) is substantially brighter than usual Type Ia supernovae used as distance indicators, Jiang and his collaborators will be able to put numerous ideas for these peculiar overluminous Type Ia supernovae to the test.
“Previously, we have constructed theoretical models of super-Chandrasekhar-mass rotating white dwarfs and their explosions. Such massive models can be consistent with the peak brightness of SN 2020hvf, but more theoretical work is necessary to explain the detailed observational properties. SN 2020hvf has provided a wonderful opportunity of collaboration between the theory and observations.” said Kavli IPMU Senior Scientist Ken’ichi Nomoto.
Jiang’s team will continue to conduct transient surveys using telescopes all across the world in order to find an answer to the long-standing origin question of Type Ia supernovae.
“We have used Type Ia supernovae to measure the expansion of the universe, although their origins are not well understood. The early-phase photometry of Type Ia supernovae provides unique information to understand their origins, and hence, should contribute to more accurate measurements of the expansion of the universe in near future,” said Kavli IPMU Senior Scientist and University of Tokyo Professor Mamoru Doi.
