SN 2021hem - an apparently "hostless" supernova in Hercules
Sun, 2021-04-04 13:47
#1
SN 2021hem - an apparently "hostless" supernova in Hercules
Supernova SN 2021hem, currently mag 16.5 and rising appears to be hostless.
The redshift of the nearest bright galaxy, LEDA 57095 approximately matches that of the supernova as measured from the spectrum but is several arcminutes away. Spectrum here Cheers Robin |
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Hmm, I wonder if it is akin to SN1987A? I doubt that the LMC would be readily visible at that distance.
Yes you would need a very deep image to be sure but the two confirmed hostless examples here
https://arxiv.org/pdf/1505.03407.pdf
are at significantly higher redshifts than this one so it should be possible to determine if it is truly hostless given time on a big telescope.
(There is no sign of anything in the DSS, SDSS 2Mass images)
Cheers
Robin
I just did a quick back of envelope check based on the LMC. using 0.9 integrated v mag and 50kpc distance gives an absolute magnitude of ~-17.5. At a distance of 150Mpc (z=0.035) this would give an apparent magnitude of ~ 18.5 which would be easily visible in the SDSS image
Cheers
Robin
Thanks.
Yes, very easily visible. I've imaged galaxies in that sort of range.
V = 16.17 +/- 0.09 on April 12.
Telescope 0.5 m f/6.8 Corrected Dall-Kirkham with f/4.5 Focal Reducer
Camera FLI PL11002M
This one also looks to be at maximum
https://alerce.online/object/ZTF21aaqwjlz
Assuming the z = 0.035 in TNS estimated from the classification spectrum equates to 150Mpc distance, this puts the absolute V magnitude at -19.7, about right for a typical type Ia with no extinction