Optical and NIR observations of the nearby type Ia supernova SN 2014J

Abstract

Optical and NIR observations of the Type Ia supernova SN 2014J in M82 are presented. The observed light curves are found to be similar to normal Type Ia supernovae (SNe Ia), with a decline rate parameter Δm₁₅(B) = 1.08 ± 0.03. The supernova reached B-band maximum on JD 2456690.14, at an apparent magnitude m_B(max) = 11.94. The optical spectra show a red continuum with deep interstellar Na i absorption, but otherwise resemble those of normal SNe Ia. The Si ii λ6355 feature indicates a velocity of ∼12 000 km s⁻¹ at B-band maximum, which places SN 2014J at the border of the normal velocity and high velocity group of SNe Ia. The velocity evolution of SN 2014J places it in the Low Velocity Gradient subclass, whereas the equivalent widths of Si ii features near B-band maximum place it at the border of the core normal and Broad Line subclasses of SNe Ia. An analytic model fit to the bolometric light curve indicates that a total of ∼1.3 M_⊙ was ejected in the explosion, and the ejected ⁵⁶Ni mass M_Ni ∼ 0.6 M_⊙. The low [Fe iii] λ4701 to [Fe ii] λ5200 ratio in the nebular spectra of SN 2014J hints towards clumpiness in the ejecta. Optical broad-band, linear polarimetric observations of SN 2014J obtained on four epochs indicate an almost constant polarization (P_R ∼2.7 per cent; θ ∼ 37°), which suggests that the polarization signal is of interstellar origin.