SN 2011ht: A weak explosion in a massive extended envelope

The possibility of explaining the light curve and the low expansion velocity of SN 2011ht, which belongs to a group of three objects showing signatures of both type IIn and type IIP supernovae, is explored. The radiated energy and expansion velocity of the ejecta of SN 2011ht are shown to be consistent with a low-energy supernova explosion (≈6 × 10⁴⁹ erg) and ≤2 \({M_ \odot }\) ejecta expanding within a circumstellar envelope of radius ~2 × 10¹⁴ cm and mass 6?8 \({M_ \odot }\) An observational test for this scenario is proposed.