Highly reddened type Ia supernova SN 2004ab: another case of anomalous extinction

TL;DR

This paper studies the highly reddened Type Ia supernova SN 2004ab, revealing its anomalous extinction properties, intrinsic parameters, and spectral classification, contributing to understanding supernova diversity and dust extinction effects.

Contribution

It provides detailed photometric and spectroscopic analysis of SN 2004ab, highlighting its anomalous low R_V value and spectral subgroup classification, which are novel insights.

Findings

Reddening E(B-V) = 1.70 mag

Low R_V = 1.41 indicating anomalous extinction

SN 2004ab classified as high velocity gradient and broad line subgroup

Abstract

We present optical photometric and spectroscopic results of supernova SN 2004ab, a highly reddened normal type Ia supernova. The total reddening is estimated as $E(B-V)$ = 1.70 $\pm$ 0.05 mag. The intrinsic decline rate parameter, $\Delta m_{15}(B)_\text{true}$ is 1.27 $\pm$ 0.05, and $B$-band absolute magnitude at maximum $M_{B}^{\text{max}}$ is $-$19.31 $\pm$ 0.25 mag. The host galaxy NGC 5054 is found to exhibit anomalous extinction with very low value of $R_V$ = 1.41 $\pm$ 0.06 in the direction of SN 2004ab. Peak bolometric luminosity is derived as $\log L_\text{bol}^\text{max}$ = 43.10 $\pm$ 0.07 erg\,s$^{-1}$. The photospheric velocity measured from absorption minimum of Si\,{\sc ii} $\lambda$6355 line shows a velocity gradient of $\dot{v}$ = 90 km\,s$^{-1}$\,d$^{-1}$, indicating that SN 2004ab is a member of the high velocity gradient (HVG) subgroup. The ratio of strength of Si\,{\sc ii} $\lambda$5972 and $\lambda$6355 absorption lines, $\cal R$(Si\,{\sc ii}) is estimated as 0.37, while their pseudo equivalent widths suggest that SN 2004ab belongs to broad line (BL) type subgroup.