Open AccessThe Type IIn supernova 1994W: evidence for the explosive ejection of a circumstellar envelope
Author(s) -
Chugai Nikolai N.,
Blinnikov Sergei I.,
Cumming Robert J.,
Lundqvist Peter,
Bragaglia Angela,
Filippenko Alexei V.,
Leonard Douglas C.,
Matheson Thomas,
Sollerman Jesper
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08011.x
Subject(s) - physics , circumstellar envelope , astrophysics , supernova , ejecta , light curve , envelope (radar) , spectral line , thomson scattering , emission spectrum , scattering , stars , astronomy , optics , telecommunications , radar , computer science
We present and analyse spectra of the Type IIn supernova (SN) 1994W obtained between 18 and 203 d after explosion. During the luminous phase (first 100 d) the line profiles are composed of three major components: (i) narrow P‐Cygni lines with the absorption minima at −700 km s −1 ; (ii) broad emission lines with blue velocity at zero intensity ∼4000 km s −1 ; and (iii) broad, smooth wings extending out to at least ∼5000 km s −1 , most apparent in Hα. These components are identified with an expanding circumstellar (CS) envelope, shocked cool gas in the forward post‐shock region, and multiple Thomson scattering in the CS envelope, respectively. The absence of broad P‐Cygni lines from the SN is the result of the formation of an optically thick, cool, dense shell at the interface of the ejecta and the CS envelope. Models of the SN deceleration and Thomson scattering wings are used to recover the density ( n ≈ 10 9 cm −3 ) , radial extent [ ∼(4–5) × 10 15 cm ] and Thomson optical depth (τ T ≳ 2.5) of the CS envelope during the first month. The plateau‐like SN light curve is reproduced by a hydrodynamical model and is found to be powered by a combination of internal energy leakage after the explosion of an extended pre‐SN (∼10 15 cm) and subsequent luminosity from CS interaction. The pre‐explosion kinematics of the CS envelope is recovered, and is close to homologous expansion with outer velocity ∼1100 km s −1 and a kinematic age of ∼1.5 yr. The high mass (∼0.4 M ⊙ ) and kinetic energy (∼2 × 10 48 erg) of the CS envelope, combined with low age, strongly suggest that the CS envelope was explosively ejected ∼1.5 yr prior to the SN explosion.