Spectrum of supernova 2020rcq


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°.



Data about supernova 2020rcq

Position: RA 11 57 14.680, DEC +49° 17' 32".00
Host galaxy: UGC 6930, z=0.00259
Discovery: 2020-08-09.168 by Zwicky Transient Facility (ZTF)
max. Brightness: V~11.8 mag (2020-08-25)
Type of SN: Ia


Image and spectrum of supernova 2020rcq

Image of supernova 2020rcq in UGC 6930
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:

Spectrum of supernova 2020rcq 2020-09-04
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.





Classification of supernova 2020rcq

The classification with two independent methods shows clearly a type Ia.

1) Classification with GELATO (Padova-Asiago Supernova Group), see [1].

Identification of supernova 2020rcq with GELATO

Identification of supernova 2020rcq 2020-09-04, best matching plot
Spectrum from 2020-09-04 best matches to SN 2005cf (Ia) with an age of 7.9 d (Quality factor: 3.16)

Identification of supernova 2020rcq 2020-09-04, matching plot #2
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].

Identification of supernova 2020rcq with SNID
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].

Part of spectrum of supernova 2020rcq with Si II absorption detail

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).




References:
[1] Harutyunyan et al., 2008, A&A, 488, 383
[2] Blondin & Tonry 2007, ApJ, 666, 1024
[3] Shappee et al. (2014) and Kochanek et al. (2017)
[4] R.O. Gray, C.J. Corbally, Stellar Spectral Classification, Princeton University Press, 2009
[5] A.V. Filippenko, Optical Spectra of Supernovae, Annu. Rev. Astron. Astrophys. 1997. 35,309,55



My other spectroscopic observations: Spektroskopie (mostly in German)



[ updated: 2021-02-06 | Email icon Gregor Krannich | Gregors astronomy page ]