We present observations of ASASSN-13dn, one of the first supernovae
discovered by ASAS-SN, and a new member of the rare group of Luminous Type II
Supernovae (LSNe II). It was discovered near maximum light, reaching an
absolute magnitude of M
v ∼ -19 mag, placing this object between
normal luminosity type II SNe and superluminous SNe A detailed analysis of the
photometric and spectroscopic data of ASASSN-13dn is performed. The spectra are
characterized by broad lines, in particular the H
α lines where we
measure expansion velocities ranging between 14000 - 6000 km s
−1 over the
first 100 days. H
α dominates the nebular spectra, and we detect a narrow
P-Cygni absorption within the broader emission line with an expansion velocity
of 1100 km s
−1. Photometrically, its light curve shows a re-brightening of
∼ 0.6 mag in the
gri bands starting at 25
±2 days after discovery,
with a secondary peak at
∼73d, followed by an abrupt and nearly linear
decay of 0.09 mag d
−1 for the next 35 days. At later times, after a drop
of 4 magnitudes from the second maximum, the light curves of ASASSN-13dn shows
softer undulations from 125 to 175 days. We compare ASASSN-13dn with other LSNe
II in the literature, finding no match to both light curve and spectroscopic
properties. We discuss the main powering mechanism and suggest that interaction
between the ejecta and a dense CSM produced by eruptions from an LBV-like
progenitor could potentially explain the observations.