4 April 2021 at 6:50 pm #574936Jeremy ShearsParticipant
Ron Arbour has asked me to post some details about this newly discovered SN and his image taken last night (2021 Apr 3).This was discovered object by Itagaki on 2021 Apr 2.The Padova-Asiago group describe this young SN as follows :-“The spectrum shows several broad features reminiscent of the early spectra of Ic-BL supernovae.A broad absorption centred at about 591.0 nm (rest frame) can be identified with SiII 635.5 nm and then an expansion velocity of about 21000 km/s is estimated. However, this feature appears much stronger that in typical Ic spectrum and more consistent with the SiII feature in SN Ia. At this stage, the classification remains uncertain.”
Attachments:4 April 2021 at 9:11 pm #584051
At ~mag 17 last night this was near my limiting magnitude for spectra but the strong features confirm a type Ia so it should get a fair bit brighter yet. Here is my spectrum compared with a match from SNID
and my spectrograph guider image4 April 2021 at 9:26 pm #584050
The Padova-Asiago classification in TNS was type I (uncertain – either Ic-BL or Ia). This has now been revised to type Ia based on a spectrum from ZTF (LT/SPRAT)
I am just reducing my spectrum taken last night.
Robin8 April 2021 at 12:32 pm #584062
I’ve just realised this is the second supernova in this galaxy this year. SN 2021do (type Ic) reached mag 16.5 mid January but is now down to mag 20
Robin8 April 2021 at 2:15 pm #584063
I see Ivan Walton caught SN2021hpr on the night of 2nd April 14 hours after discovery in this member’s image
crop below9 April 2021 at 1:10 pm #584065Stewart John BeanParticipant
This is an image from 2021-04-09 09:00:20 obtained from New Mexico using iTel 021. 3 x 300 s exposure in V filter.10 April 2021 at 8:25 am #584078Stewart John BeanParticipant
Vphot estimates the SN to be at V mag 14.8510 April 2021 at 11:31 pm #584083David SwanParticipant
This SN is in a lovely host galaxy. Picture taken 10 Apr.11 April 2021 at 10:18 am #584085Maxim UsatovParticipant
Measured it at V = 14.665 ± 0.04.
Telescope 0.43-m f/6.8 reflector with f/4.5 focal reducer
Camera FLI PL6303E13 April 2021 at 2:05 pm #584090
It looks like it is now close to maximum.
At a distance of 40Mpc (from NED) an apparent magnitude of 14.6 gives an absolute mag of -18.4 not allowing for any extinction
An ALPY200 spectrum from last night continues to give a good match to a type Ia at the host redshift
Robin18 April 2021 at 2:04 pm #584101David StrangeParticipant
Caught this spectrum of SN2021hpr last night. It’s a 20 x120s stack with a Star Analyser 100, C9 and ASI183MM, but only problem was my calibration using the bright A0V star Izar looked oversaturated and I couldn’t get a useful calibration for one point alignment. Does the SN spectrum look about right?
David18 April 2021 at 4:18 pm #584102
All is not lost. There is a field star showing a nice telluric absorption band at ~7620A which you can use to get an approximate wavelength calibration. (~25A/pixel off the posted image but that may have been reduced down from the original)
Robin18 April 2021 at 4:50 pm #584103
That would make this deep absorption the characteristic Si II line18 April 2021 at 6:42 pm #584104David StrangeParticipant
Thanks very much Robin for your thinking outside the box! That never occurred to me!
David19 April 2021 at 9:16 pm #584106Mike HarlowParticipant
I’ve attached my recent objective prism spectrum not because it shows anything new but to illustrate a trick used for line identification. (Taken on 12th April 2021).
I usually image and take spectra through an Astrodon luminance filter which has a sharp cut-off at 700nm. The result is that all spectra cut-off at that wavelength giving an internal reference on all the spectra in the field. Coupled with the dispersion equation for the prism this enables reasonable estimates for line positions. In the spectrum of SN2021hpr the first absorption below 700nm is the Si II line as shown nicely in Kevin Gurney’s spectrum (of another type-Ia SN) and those above.
I can’t claim any originality here, this was a trick used by professional astronomers conducting objective prism surveys in the 1960s, 70s and 80s. Some of the photographic plates used had sharp spectral cut-offs imprinting a known wavelength on their spectra. And when you have a Schmidt photographic plate with 1000s of spectra on it that’s really useful!
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