A Type II core-collapse supernova called SN 2020fqv exploded in NGC 4568, a member of a pair of colliding unbarred spiral galaxies; the other member of the eye-catching pair is NGC 4567. Also known as the Butterfly Galaxies or the Siamese Twins, the system is located about 60 million light-years away in the constellation of Virgo.
False-color image of SN 2020fqv in its host galaxy system NGC 4567 and NGC 4568; the location of the supernova is shown in the inset. The image is composed of a pre-explosion single-band HST/WFPC2 image in the F606W filter with the color information from ground-based images obtained using the Nickel Telescope at Lick Observatory. The image of SN 2020fqv and the area outside of HST field of view is also from Nickel. Image credit: Joseph Depasquale / STScI.
The Type II supernova SN 2020fqv, also designated as ZTF20aatzhhl, was discovered on April 1, 2020 by the Zwicky Transient Facility at the Palomar Observatory.
The stellar explosion was simultaneously observed with NASA’s Transiting Exoplanet Survey Satellite (TESS), the NASA/ESA Hubble Space Telescope, and a suite of ground-based telescopes.
Together, these observatories gave the first holistic view of a star in the very earliest stage of destruction.
Hubble probed the material very close to the star, called circumstellar material, mere hours after the explosion. This material was blown off the star in the last year of its life.
These observations allowed astronomers to understand what was happening to the star just before it exploded.
“We rarely get to examine this very close-in circumstellar material since it is only visible for a very short time, and we usually don’t start observing a supernova until at least a few days after the explosion,” said Dr. Samaporn Tinyanont, an astronomer in the Department of Astronomy and Astrophysics at the University of California, Santa Cruz.
“For this supernova, we were able to make ultra-rapid observations with Hubble, giving unprecedented coverage of the region right next to the star that exploded.”
Dr. Tinyanont and colleagues used three different methods to determine the mass of the progenitor star of SN 2020fqv.
These included comparing the properties and the evolution of the supernova with theoretical models; using information from a 1997 Hubble image of the star to rule out higher-mass stars; and using observations to directly measure the amount of oxygen in the supernova, which probes the mass of the star. The results are all consistent: between 14 and 15 solar masses.
“People use the term ‘Rosetta Stone’ a lot. But this is the first time we’ve been able to verify the mass with these three different methods for one supernova, and all of them are consistent,” Dr. Tinyanont said.
“Now we can push forward using these different methods and combining them, because there are a lot of other supernovae where we have masses from one method but not another.”
In the years before stars explode, they tend to become more active. Some astronomers point to the red supergiant Betelgeuse, which has recently been belching significant amounts of material, and they wonder if this star will soon go supernova.
“This could be a warning system. So if you see a star start to shake around a bit, start acting up, then maybe we should pay more attention and really try to understand what’s going on there before it explodes,” said Dr. Ryan Foley, also from the Department of Astronomy and Astrophysics at the University of California, Santa Cruz.
“As we find more and more of these supernovae with this sort of excellent data set, we’ll be able to understand better what’s happening in the last few years of a star’s life.”
The results will be published in the Monthly Notices of the Royal Astronomical Society.
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Samaporn Tinyanont et al. 2021. Progenitor and Close-In Circumstellar Medium of Type II Supernova 2020fqv from High-Cadence Photometry and Ultra-Rapid UV Spectroscopy. MNRAS, in press; arXiv: 2110.10742
