Nova Cas 2021 (=V1405 Cas) is a neon nova
ATel #15796; U. Munari (INAF Padova) and P. Valisa (ANS Collaboration)
on 7 Dec 2022; 17:23 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)
With the Varese 0.84m and Asiago 1.82m telescopes we are keeping a tight
Echelle high-resolution monitoring of Nova Cas 2021 since its eruption on 18
March 2021 (ATel #14476, #14614, #15093). Sparser visits at near-UV
wavelengths are carried out with the Asiago 1.22m telescope, and on our last
spectrum of Nov Cas 2021 obtained with that telescope on 27 Nov 2022 (2.31
Ang/pix, range 3320-8020 Ang), day +618 into the outburst, [NeV] 3427 is
extremely intense, the brightest emission line of the whole optical range.
[NeIV] and [NeIII] are also present in emission. The spectrum can be viewed
at this link. The table below lists the integrated absolute flux (in
erg/cm2/s) of the most representative emission lines present on
the 27 Nov 2022 spectrum, corrected for the E(B-V)=0.53 interstellar
reddening affecting Nova Cas 2021 following Munari et al. (2021, ATel,
14476) and adopting the Fitzpatrick (1999, PASP 111, 63) extinction law.
| line | Ang | flux |
|---|
| Ha | 6563 | 8.865E-11 |
| [FeVII] | 6087 | 3.150E-11 |
| [CaV] | 5309 | 1.178E-11 |
| [FeVI] | 4969 | 1.754E-11 |
| Hb | 4861 | 3.535E-11 |
| [NeIV] | 4720 | 4.671E-12 |
| HeII | 4686 | 5.840E-11 |
| [NeIII] | 3869 | 1.793E-11 |
| [NeV] | 3427 | 1.214E-10 |
| [NeV] | 3346 | 4.534E-11 |
The overwhelming intensity of [NeV] indicates that Nova Cas 2021 is a
neon nova. Takeda and Diaz (2019, PASP 131, 054205) report that
only about 20 novae have been classified in the neon class, i.e.
showing an overabundance of neon in the ejecta, inherited from a massive (>1
Msun) O-Ne central WD (Hachisu and Kato 2016, ApJ 816, 26). Recent examples
of neon novae includes V1674 Her (ATel #14746) and V392 Per (ATel #11926).
Spectrum of Nova Cas 2021 for 27 Nov 2022
