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Observation by Robin Leadbeater: SN 2021zny - A “Super-Chandrasekha...

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Robin Leadbeater


Robin Leadbeater


2021 Oct 10 - 22:22


2021 Oct 19 - 16:46



  • ALPY 200 Spectrograph
  • ATK 314 camera
  • Celestron C11 SCT 280mm aperture f5.5

250 min (25x600s) over 3 nights


Wigton Cumbia

Target name

SN 2021zny in 2MFGC 1570


SN 2021zny - A “Super-Chandrasekhar” 1a Supernova ?

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SN 2021zny - A “Super-Chandrasekhar” 1a Supernova ?

SN 2021zny was discovered by the Zwicky Transient Facility on 2021-09-22 and classified as a type 1a-SC  supernova by Masayuki Yamanaka using the KOOLS-IFU spectrograph attached to the 3.8-m Seimei telescope at the Okayama Observatory

1a-SC sub-type supernovae are rare (only around a dozen are known) and were originally considered to involve the thermonuclear explosion of a progenitor significantly more massive than the Chandrasekhar limit for a normal type 1a, though more recently alternative scenarios have been proposed not involving breaching the Chandrasekhar limit. This recent reference provides an overview. 

The spectrum here was taken 3 weeks after discovery around maximum light at mag 16 using my ALPY 200 faint object spectrograph and is a composite of 3 nights observations under generally poor conditions in an attempt to improve the signal/noise ratio. The classifiers of SN 2021zny noted the  similarity of their spectrum with that of SN 2009dc, considered an archetype of this sub-class of 1a supernovae.  The supernova classification program GELATO confirms the continuing similarity with SN 2009dc in my spectrum. The luminosity at maximum light appears to match that expected for a normal type 1a but the full light curve and later spectra will likely provide further information. If it does turn out to be a type 1a-SC, expect to see papers on it in future.


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