We present optical and infrared monitoring data of SN 2012hn collected by the Public ESO Spectroscopic Survey for Transient Objects ( PESSTO ) .
We show that SN 2012hn has a faint peak magnitude ( M _ { R } \sim -15.65 ) and shows no hydrogen and no clear evidence for helium in its spectral evolution .
Instead , we detect prominent Ca ii lines at all epochs , which relates this transient to previously described ‘ Ca-rich ’ or ‘ gap ’ transients .
However , the photospheric spectra ( from -3 to +32 d with respect to peak ) of SN 2012hn show a series of absorption lines which are unique , and a red continuum that is likely intrinsic rather than due to extinction .
Lines of Ti ii and Cr ii are visible .
This may be a temperature effect , which could also explain the red photospheric colour .
A nebular spectrum at +150 d shows prominent Ca ii , O i , C i and possibly Mg i lines which appear similar in strength to those displayed by core-collapse SNe .
To add to the puzzle , SN 2012hn is located at a projected distance of 6 kpc from an E/S0 host and is not close to any obvious starforming region .
Overall SN 2012hn resembles a group of faint H-poor SNe that have been discovered recently and for which a convincing and consistent physical explanation is still missing .
They all appear to explode preferentially in remote locations offset from a massive host galaxy with deep limits on any dwarf host galaxies , favouring old progenitor systems .
SN 2012hn adds heterogeneity to this sample of objects .
We discuss potential explosion channels including He-shell detonations and double detonations of white dwarfs as well as peculiar core-collapse SNe .