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We present observations of two new hydrogen-poor superluminous supernovae(SLSN-I), iPTF15esb and iPTF16bad, showing late-time H-alpha emission with lineluminosities of (1-3)e+41 erg/s and velocity widths of (4000-6000) km/s.Including the previously published iPTF13ehe, this makes up a total of threesuch events to date. iPTF13ehe is one of the most luminous and the slowestevolving SLSNe-I, whereas the other two are less luminous and fast decliners.We interpret this as a result of the ejecta running into a neutral H-shelllocated at a radius of ~ 1.0e+16cm. This implies that violent mass loss musthave occurred several decades before the supernova explosion. Such a short timeinterval suggests that eruptive mass loss could be common shortly prior to thedeath of a massive star as a SLSN. And more importantly, helium is unlikely tobe completely stripped off the progenitor stars and could be present in theejecta. It is a mystery why helium features are not detected, even thoughnon-thermal energy sources, capable of ionizing He atoms, may exist assuggested by the O II absorption series in the early time spectra. At latetimes (+240d), our spectra appear to have intrinsically lower [O I]6300Aluminosities than that of SN2015bn and SN2007bi, possibly an indication ofsmaller oxygen masses (<10-30Msun). The blue-shifted H-alpha emission relativeto the hosts for all three events may be in tension with the binary star modelproposed for iPTF13ehe. Finally, iPTF15esb has a peculiar light curve withthree peaks separated from one another by ~ 22 days. The LC undulation ishigher in bluer bands. One possible explanation is eject-CSM interaction.

Hydrogen-poor Superluminous Supernovae With Late-time H-alpha Emission: Three Events From the Intermediate Palomar Transient Factory