Type II intermediate-luminosity optical transients (ILOTs)

We propose that in a small fraction of intermediate-luminosity optical transients (ILOTs) powered by a strongly interacting binary system, the ejected mass in the equatorial plane can block the central source from our line of sight. We can therefore observe only radiation that is reprocessed by polar outflow, much as in type II active galactic nuclei. An ejection of M_ej,e = 10⁻⁴ M☉(1 M☉) at 30^◦ from the equatorial plane and at a velocity of v_e = 100 km s⁻¹ will block the central source in the near-infrared for about 5 yr (500 yr). During that period of time, the object might disappear in the visible band, and can be detected only in the IR band due to polar dust. We raise the possibility that the recently observed disappearance of a red giant in the visible, designated N6946-BH1, is a type II ILOT rather than a failed supernova. For this case, we estimate that the ejected mass in the polar direction was M_ej,p ≈ 10⁻³ M☉. Our scenario predicts that this event should reinstate its visible emission in several decades.