SN2016coj was the brightest supernova in the year 2016. With V=13.1 mag it was reachable whithin the Alpy600 spectrograph.
This supernova has a comfortable distance to the nucleus of the elliptical galaxy NGC 4125. It could be placed in a separate position
at the entrance slit. Despite of the continuous bad weather period in June, on 2016-06-17 there was a small time slot
with clear sky. I used this to record the spectrum of sn2016coj. This is my first supernova spectrum!
Image and spectrum of supernova 2016coj in NGC 4125
2016-06-10 21:14 - 21:27 UT, Roof Observatory Kaufering, Meade 14" ACF telescope on Taurus GM-60 mount, CCD: Moravian G2-8300FW, 3x3 binning, L-filter,
exposure: 12x60s; magnitude measured with Astrometrica: 13.1mag;
see 2016coj at 2016 Supernovae archive page.
Here is my spectrum of this supernova:
2016-06-17 21:55 - 23:01 UT, Roof Observatory Kaufering, Meade 14" ACF telescope on Taurus GM-60 mount, Astro Physics reducer CCDT67,
Alpy600 with guiding unit, CCD camera: Atik 428EX, guiding camera: ASI 120 MM; recording software: AstroArt, guiding software: PHD;
Wavelength calibration: Hg lines from energy saving lamp and Ne lines from a flicker flame light bulb,
instrumental response calibration with reference star HD106591 (Delta Ursae Majoris, A3V), data reduction with
Integrated Spectrographic Innovative Software from Christian Buil;
The spectrum has been cut at the near UV end (3800 Å) due to strong noise.
The classification with two independent methods confirms the already known type Ia nine days after its maximum of this sn, see
TNS page.
1) Classification with GELATO
(Padova-Asiago Supernova Group), see [1].
2) Classification with SNID
(SuperNova IDentification), see [2].
Identification and discussion
The features in supernova spectra are all broad due to the very high ejection velocities, which typically are in excess of 10.000 km/s [3].
According to [4] the ejection velocity in SN2016coj is about 15400 +/- 100 km/s (at age -6 d). A prominent feature in early type Ia supernovae
is a strong absorption at around 6150 Å due to Si II. This is a blueshifted blend of the rest wavelengths Si II λλ6347, 6371 [5].
Other absorption features are from S II, Fe II, Co II, Ca II and O I [5],[6].
Labeled spectrum:
The absorption features Ca II H&K at λλ3934, 3968 and O I at about λ7460 are not seen in my spectrum due to strong noise at the ends.
I measured the Si II absorption at 6129.5 Å in my spectrum.
The value of blueshift is 255.5 Å against the rest wavelength at 6355 Å. This corresponds
to a radial velocity of 11.979 km/s of the ejected material (with correction of z=0.00448 from host galaxy NGC4125). A result that conforms nicely to the
spectrum fom [7] recorded 9 days earlier than my spectrum.
