SN 2017egm is a helium-rich superluminous supernova, study finds

Utilizing numerous ground-based and space observatories, a world staff of astronomers has investigated a close-by supernova designated SN 2017egm. Because of this, they discovered that the inspected explosion belongs to a uncommon group of helium-rich superluminous supernovae. The discovering is reported in a paper revealed March 6 on the arXiv pre-print server.

Supernovae (SNe) are highly effective and luminous stellar explosions. They’re vital for the scientific community as they provide important clues into the evolution of stars and galaxies. Normally, SNe are divided into two teams based mostly on their atomic spectra: Sort I and Sort II. Sort I SNe lack hydrogen of their spectra, whereas these of Sort II showcase spectral traces of hydrogen.

Superluminous supernovae (SLSNe) are characterised by exceptionally vivid, usually long-lived gentle curves. Interplay of the SN ejecta with surrounding circumstellar materials (CSM) is an efficient mechanism to transform kinetic power of the ejecta into radiation and it’s assumed that such a course of might energy SLSNe. As with regular SNe, SLSNe are additionally categorized into two lessons based mostly on their spectra round most gentle: hydrogen-poor (SLSNe-I) and hydrogen-rich occasions (SLSNe-II).

SN 2017egm (also referred to as Gaia17biu) is an SLSNe-I found by the Photometric Science Alerts Workforce of ESA’s Gaia mission on Could 23, 2017, at a redshift of 0.03. Its host galaxy, NGC 3191, is huge and has a near-solar metallicity, in distinction to the everyday dwarf and metal-poor host galaxies for SLSNe-I. SN 2017egm was the closest hydrogen-poor superluminous supernova when found.

Lately, a staff of astronomers led by Jiazheng Zhu of the College of Science and Expertise of China in Hefei, China, carried out photometric and spectroscopic SN 2017egm to be able to get extra insights into its properties.

“On this paper, we current probably the most full photometric and spectroscopic evaluation of SN 2017egm, taking our observational data and all public knowledge collectively,” the researchers wrote.

The research discovered that the long-term multiband gentle curves of SN 2017egm spanning about 300 days have a pointy peak, rapid decline, and a number of late-time bumps. Furthermore, the spectra of this SLSN showcase sturdy helium traces.

Based mostly on these findings, the astronomers categorized SN 2017egm into the subclass of slowly-evolving SLSNe-I in keeping with the luminosity and colour evolution close to peak brightness. As a result of presence of the helium options, they additional labeled SN 2017egm as an helium-rich superluminous supernova (SLSN-Ib), which is a uncommon but accumulating subpopulation of SLSNe-I.

The analysis additionally discovered that SN 2017egm had a big infrared extra, at a degree of 100 million solar luminosities, suggesting dust echoes from a pre-existing dust shell or emission from newly fashioned dust. The authors of the paper estimate that SN 2017egm had an ejecta mass of roughly 10.7 solar lots.

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