Observation by Robin Leadbeater: slitless spectrum of SN 2021hiz

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Robin Leadbeater


Robin Leadbeater


2021 Apr 05 - 22:24


2021 Apr 06 - 14:44



  • Star Analyser 100 lines/mm diffraction grating
  • Celestron CII at ~f6
  • ATK428 camera

132 x 20 sec


Wigton Cumbria

Target name

SN 2021hiz in UGC 7513


slitless spectrum of SN 2021hiz

About this image

At ~mag 14 this supernova  in UGC7513 had become bright enough and was sufficiently isolated from the galaxy background for a slitless spectrum. 

I used a low dispersion (19A/pixel) to give a bright spectrum against the sky background. The camera was rotated so the galaxy was vertical to avoid contamination from the galaxy and other the stars and spectra. This also allowed  the galaxy spectrum to be approximately removed using sky background subtraction zones directly above and below the supernova.

A spectrum of nearby mag 5.6 type A2v star HD110423 was used for  wavelength and flux calibration (correcting for instrument response and atmospheric extinction)

Although very low resolution (~80Angstrom) the spectrum shows the clear broad absorption lines characteristic of a type Ia supernova, particularly the SiII 6355A line redshifted by the galaxy redshift and blue shifted by the velocity of the explosion to give an estimated velocity of the ejecta of ~12300km/s.

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