SN 2016B a.k.a. ASASSN-16ab: a transitional Type II supernova

We present photometry, polarimetryand spectroscopy of the Type II supernovaASASSN-16ab/SN 2016B in PGC 037392. The photometric and spectroscopic follow-up commenced about two weeks after shock breakoutand continued until nearly six months. The light curveof SN 2016B exhibits intermediate properties between those of Type IIP and IIL. The early decline is steep (1.68 $\pm$ 0.10 mag 100 d$^{-1}$), followed by a shallower plateau phase (0.47 $\pm$ 0.24 mag 100 d$^{-1}$). The optically thick phase lasts for 118 d, similar to Type IIP. The $^{56}$Ni mass estimated from the radioactive tail of the bolometric light curveis 0.082 $\pm$ 0.019 M$_\odot$. High velocity component contributing to the absorption trough of H$\ alpha$ and H$\beta$ in the photospheric spectra are identified from the spectral modelling from about 57 - 97 d after the outburst, suggesting a possible SN ejectaand circumstellar material interaction. Such high velocity features are common in the spectra of Type IIL supernovae. By modelling the true bolometric light curveof SN 2016B, we estimated a total ejected mass of $\sim$15 M$_\odot$, kinetic energy of $\sim$1.4 foe and an initial radius of $\sim$400 R$_\odot$.