Spectrum of supernova 2017hcc


SN 2017hcc is a bright supernova in an anonymous galaxy in constellation Cetus. With maximum brightness of V=13.6 mag it is reachable whithin the Alpy600 spectrograph, but it needs excellent weather conditions to take a spectrum. At my location the object reaches a maximum altitude of 30.6°, which is barely helpful.



Data about supernova 2017hcc

Position: RA 00h 03m 50s.580, DEC -11° 28' 28".78
Host galaxy: anonymous galaxy
Discovery: 2017-10-02.378 by ATLAS
Brightness: V=13.6 mag
Type of SN: IIn


Image and spectrum of supernova 2017hcc

Image of supernova 2017hcc
2017-12-24 17:08 - 17:46 UT, Roof Observatory Kaufering, Meade 14" ACF telescope on Taurus GM-60 mount, CCD: Moravian G2-8300FW, 3x3 binning, L-filter, exposure: 29x60s; magnitude measured with Astrometrica: 14.1 mag; See 2017hcc at Latest Supernovae page for more information and images.



Here is my spectrum of this supernova:

Spectrum of supernova 2017hcc 2017-11-22
2017-11-22 18:47 - 21:06 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 flicker flame light bulbs, instrumental response calibration: with reference star HD 1064, B8.5 V, data reduction: with Integrated Spectrographic Innovative Software from Christian Buil;
The spectrum has been cut at the near UV end (3810 Å) due to strong noise.





Classification of supernova 2017hcc

The classification with two independent methods isn't clear this time. GELATO indicates this supernova as type II with attribute unreliable, whereas SNID best matches the spectrum to an AGN. According to TNS [3] and Prieto et al. [4] it is a type IIn.

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

Identification of supernova 2017hcc with GELATO

Identification of supernova 2017hcc 2017-11-22
Spectrum from 2017-11-22 best matches to SN 2008fz (IIn) with age of 48.6 d (Quality factor: 1.26).


2) Classification with SNID (SuperNova IDentification), see [2].

Identification of supernova 2017hcc with SNID
Spectrum from 2017-11-22 best matches to an AGN, which is wrong.

Identification of supernova 2017hcc with SNID
The 10th template matches to SN 1996L (IIn) with age of 59 d. SNID doesn't lead to a reliable result in this case.

In both tools the red shift (z=0.017) of host galaxy has been entered.

Note: The age in GELATO is given in days since explosion, wheras the age in SNID is given in days since maximum brightness.



Line identification and discussion

Type IIn supernovae are a subclass of type II, which has been introduced in the 1990s. The "n" means narrow lines. The emission lines have usually broad bases and a narrow tips. The narrow components are produced by ionized gas and the broader components are produced by the shock of colliding supernova ejecta with dense circumstellar material. A more detailed description of type IIn supernovae is given in COSMOS (The SAO Encyclopedia) [5].

Identification of emission lines in spectrum of sn2017hcc

My spectrum shows a strong blue continuum and red shifted Balmer emission lines. He I emission is not clearly detectable due to the noise. I measured the H-Alpha and H-Beta emission lines at their narrow tips:

H-Alpha 6673.2 Å zcorr=0.0167
H-Beta 4947.7 Å zcorr=0.0177

The arithmetic mean of both heliocentric corrected z-values is z=0.0172, which is the redshift of the host galaxy. A more precise value (z=0.0168) has been determined by Prieto et al., see [4].




References:
[1] Harutyunyan et al., 2008, A&A, 488, 383
[2] Blondin & Tonry 2007, ApJ, 666, 1024
[3] TNS, https://wis-tns.weizmann.ac.il//object/2017hcc
[4] Prieto et al. 2017, https://arxiv.org/pdf/1711.07938.pdf
[5] Type IIn Supernovae in COSMOS (The SAO Encyclopedia of Astronomy)



My other spectroscopic observations: Spektroskopie (German)



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