Assuming it does not get any

Home Forums Spectroscopy SN2019ein – an unusual supernova ? Assuming it does not get any

Robin Leadbeater

Assuming it does not get any brighter, the magnitude is about right for a Ia at the distance of NGC5353, perhaps a little faint but I think it is particularly tricky to measure redshift from Ia supernova spectra. Unlike type II where at least you have H alpha emission unshifted by the explosion velocity, you just have broad absorption lines blue shifted by the explosion, the velocity of  which reduces with time. If I understand correctly how SNID for example estimates the age and redshift, it attempts to simultaneously fit these two parameters, comparing with other spectra in the library. It can be significantly out at times though. It is possible that the explosion velocity is higher than usual as suggested by the original classifiers, which could then throw out the redshift estimate. Also the published redshift of NGC5353 is probably for the nucleus and this SN is in the outer regions where the radial velocity might be different. The light curve should eventually give the age though which perhaps will pin things down better.