Thank you for this acurate description Paolo
According to ATel 5818, the interstellar extinction is E(B-V) = 1.2
which confirms your continuum and the strong Na I D interstellar line
François
ATEL #5818 ATEL #5818
Title: SN2014J spectroscopic and photometric data
Author: INAF-Astronomical Observatory of Bologna
Queries:
giuseppe.altavilla@oabo.inaf.it
Posted: 27 Jan 2014; 10:44 UT
Subjects:Optical, Star, Supernovae
Spectra and BVR images of the supernova SN 2014J in the nearby galaxy M82
were obtained on
Jan. 23.05 2014 (UT) a the 1.5m G.D. Cassini Telescope (Loiano) with BFOSC
by G. Altavilla, R. Gualandi and I. Bruni. The spectra, obtained with gr4,
gr7 and gr8 and a 2" slit, cover the ~3500-8000 A range with a resolution
of ~12, ~6 and ~6 A respectively. The expansion velocity measured from
the SiII line (6355A) is ~13900km/s while SII (5640)A gives ~12000 km/s.
The best matches obtained with the GEneric cLAssification TOol (GELATO,
Harutyunyan et al. 2008, A.Ap. 488, 383; available at URL
https://gelato.tng.iac.es/login.cgi)
are with SN2000fa (Ia at 12 days before maximum) and SN1997do (Ia at 8
days before maximum).
Magnitude estimates for the same night (JD 2456680.55208) are the following:
B=12.72+-0.14, V=11.52+-0.23, R 11.05 +-0.05. To be noted the corresponding
colour: B-V=1.2 (instead of B-V~0 for a normal type Ia at the same epoch),
supported by the strong NaD features visible in the spectra.