Spectra of Nova Cassiopeiae 2020


The Nova Cassiopeiae 2020 (=ASASSN-20jg = TCP J00114297+6611190) is a bright galactic nova in constellation Cassiopeia. The discovery magnitude was 12.9 mag (unfiltered CCD) [1]. The nova peaked around 10th August with a brightness of 10.8 mag (see light curve). With this brightness it is easy reachable with the Alpy600 spectrograph, but it needs good weather conditions to take a spectrum. I took an image and three spectra:



Data about Nova Cas 2020

Position: RA 00h 11m 42.96s, DEC +66° 11' 20.8"
Progenitor: unknown
Discovery: 2020 July 27.930 UT by S. Korotkiy on images of NMW survey (Sokolovsky et al. 2014, ASPC, 490, 395)
Brightness: V=12.9 mag (at discovery date), V=11.1 mag (2020-08-08.941 UT), see light curve of Nova Cas 2020


Image and spectrum of Nova Cas 2020

Image of Nova Cas 2020
2020-08-08 22:28 - 22:42 UT, Roof Observatory Kaufering, Meade 14" ACF telescope on Taurus GM-60 mount, CCD: Moravian G2-8300FW, 3x3 binning, L-filter, exposures: 60x10 sec; magnitude measured with Astrometrica: V=11.1 mag; click to uncrop image;

For other images see



Here are my spectra of this nova:

Spectrum of Nova Cas 2020, Aug 9th
2020-08-09 01:24 - 02:37 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 HIP 531 (=10 Cas), B9 IIIe, data reduction: with Integrated Spectrographic Innovative Software from Christian Buil;


Spectrum of Nova Cas 2020, Aug 15th
2020-08-15 22:51 - 00:53 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 HIP 531 (=10 Cas), B9 IIIe, data reduction: with Integrated Spectrographic Innovative Software from Christian Buil;


Spectrum of Nova Cas 2020, Sep. 5th
2020-09-04 23:49 - 01:56 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 HIP 531 (=10 Cas), B9 IIIe, data reduction: with Integrated Spectrographic Innovative Software from Christian Buil;


Line identification and discussion

Here is the labeled spectrum from 2018-08-09:
labelled spectrum of Nova Cas, Aug 9th

The signal in blue is very low and the spectrum consists of DIBs (diffuse interstellar bands). Both are indications that the Nova is strongly reddened due to interstellar extinction. This is also shown in ATEL#13905 [2]. Compaired with a spectrum from Dr. Narusawa, FKO Japan at 2020-08-10.724 shows that the H-Beta emission line has vanished and that the P-Cygni profiles on Balmer lines have strenghtened only 1,6 days later [4].

Here is the labeled spectrum from 2020-09-05:
labelled spectrum of Nova Cas 2020, Sep 5th

Compared to spectrum from 2020-08-15 the H-Alpha line (tip at value ~18) and other Balmer lines have strenghtened. The forbidden OI lines and the FeII lines have intensified as well. Higher Balmer and FeII lines have blueshifted absorptions (P-Cygni profiles), which is hard to see in my spectrum, but they are present in spectra with higher resolution at the same date, see [6]. Very early the nova has been classified as classical FeII type (Jul 29, 2020) [1]. The identification of spectral lines succeeded with the help of [7] and [8].


Spectra evolution of Nova Cas 2020

Here are the spectra for comparison, they are shifted in y-direction by 7 units each for better distinction:
Nova Cas 2020 spectra evolution





References:
[1] Nova Cas 2020 in ATel#13903
[2] Nova Cas 2020 in ATel#13905
[3] AAVSO Alert Notice #715
[4] Nova Cas 2020 spectra from Dr. Shin-ya Narusawa (Fujii Kurosaki Observatory, Japan)
[5] Nova Cas 2020 in Spectro-ARAS forum
[6] Light curves and spectra of Nova Cassiopeiae 2020 (accompany ATels #13903, #13904, #13919, #14004)
[7] T. Iijima et al., A&A 482, 865-877 (2008), Spectroscopic observations of the first helium nova V445 Puppis
[8] G. C. Anupama, ASI ConferenceSeries,2012,Vol. 6, pp 143 - 149, Classification of nova spectra



My other spectroscopic observations: Spektroskopie (German)



[ updated: 2021-02-14 | Email icon Gregor Krannich | Gregors astronomy page ]