SN 2020rcq is a bright supernova in emission line galaxy UGC 6930 in constellation UMa. With actual brightness of V~12.5 mag it is still reachable whithin the Alpy600 spectrograph,
but it needs good weather conditions. At start time of the spectroscopy session the object had an altitude of 25°, at the end it was quite low at 14°.
I took a spectrum on 2020-09-04 in the evening with the following conditions: mostly clear sky, moon (93%) at the end, low humidity, average seeing, wind: light breeze, temperature: 20° C
2020-09-08 19:43 - 20:17 UT, Roof Observatory Kaufering, 14" ACF teleskop on Taurus GM-60 mount, CCD camera: Moravian G2-8300FW, 3x3 Binning, L-filter, 60x30s; magnitude measured with Astrometrica: V=12.7 mag;
See SN 2020rcq at Latest Supernovae page for more information and images.
Here is my spectrum of this supernova:
2020-09-04 19:34 - 21:26 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: PHD2
Wavelength calibration: Hg lines from energy saving lamp and Ne lines from flicker flame light bulbs,
instrumental response calibration: with reference star Gamma UMa (HD 103287), A0 Ve, data reduction: with
Integrated Spectrographic Innovative Software from Christian Buil;
The spectrum has been cut at the near UV end (3720 Å) due to strong noise.
The classification with two independent methods shows clearly a type Ia.
1) Classification with GELATO
(Padova-Asiago Supernova Group), see [1].
Spectrum from 2020-09-04 best matches to SN 2005cf (Ia) with an age of 7.9 d (Quality factor: 3.16)
Spectrum from 2020-09-04 plot #2 matches SN 2003du (Ia) with an age of 8.1 d (Quality factor: 2.92) - visually a better match
2) Classification with SNID
(SuperNova IDentification), see [2].
Spectrum from 2020-09-04 best matches to SN 2003du (Ia-norm) with an age of 8 d
In both tools the red shift (z=0.00259) of host galaxy has been entered.
Assuming an age of 8 d, the maximum brightness must have been around Aug 27th 2020.
Unfortunately there is no light curve available at ASASSN Sky Patrol [3].
Note: The age in both tools (GELATO and SNID) is given in days since maximum brightness.
Line identification and discussion
The features in supernova spectra are all broad due to the very high ejection velocities, which typically are in excess of 10000 km/s [4]. A prominent feature in early type Ia supernovae is a strong absorption at around 6160 Å due to Si II. This is a blueshifted blend of the rest wavelengths Si II λλ6347, 6371 [5].
The value of blueshift is 188.6 Å against the rest wavelength at 6355 Å. This corresponds
to a radial velocity of 9674 km/s of the ejected material (with correction of z=0.00259 from host galaxy UGC 6930).
