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

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, $\mathrm{\Delta }{m}_{15}(B{)}_{\text{true}}$ 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, $\mathcal{R}$(Si,{\sc ii}) is estimated as 0.37, while their pseudo equivalent widths suggest that SN 2004ab belongs to broad line (BL) type subgroup.