Abstract:
We present results based on follow-up observations of the Type II-plateau supernova (II-P
SN) 2013ej at six epochs spanning a total duration of
∼
37 d. The
R
C
-band linear polarimetric
observations were carried out between the end of the plateau and the beginning of the nebular
phase, as demarcated in the photometric light-curve. The contribution arising from interstellar
polarization (ISP) was constrained using two approaches, namely based on observations
of foreground stars lying within a 5-arcmin and a 10
◦
radius of the SN location, and by
investigating the extinction arising from the Milky Way and host galaxy in the direction of the
SN. Our analysis revealed that in general the intrinsic polarization of the SN was higher than
the polarization values for the foreground stars and exhibited an increasing trend during our
observations. After correcting for the ISP of
∼
0.6 per cent,the maximum intrinsic polarization
of SN 2013ej was found to be 2.14
±
0.57 per cent. Such a strong polarization has rarely
been seen in II-P SNe. If this procedure is justified (i.e. the ‘polarization bias’ effect is indeed
negligible) the polarization could be caused by the asymmetry of the inner ejecta of the SN,
because the ISP towards the SN location is estimated to be, at most, 0.6 per cent.
