Supernova light curves pow ered by young m agnetars

TLDR: In this article, the authors show that energy injected into an expanding supernova by a highly magnetic (B � 5 � 10 14 G)neutron starspinning at an initial period of Pi 2 20 m scan substantially brightens the lightcurve.

Abstract: W e show thatenergy deposited into an expanding supernova rem nantby a highly m agnetic (B � 5 � 10 14 G)neutron starspinning atan initialperiod of Pi � 2 20 m scan substantially brighten the lightcurve. Form agnetarswith param etersin thisrange,the rotationalenergy isreleased on a tim escaleofdaysto weeks,which iscom parableto theeectivediusion tim ethrough thesupernova rem nant.Thelatetim eenergyinjectioncanthenberadiatedwithoutsueringoverwhelm ingadiabatic expansion losses. The m agnetar input also produces a centralbubble which sweeps ejecta into an internaldense shell,resulting in a prolonged period ofnearly constantphotospheric velocity in the observed spectra.W ederiveanalyticexpressionsforthelightcurverisetim eand peak lum inosity as a function of B, Pi and the propertiesofthe supernova ejecta thatallow fordirectinferencesabout the underlying m agnetar in bright supernovae. W e perform num ericalradiation hydrodynam ical calculations ofa few specic instances and com pare the resulting light curves to observed events. M agnetaractivity is likely to im pact m ore than a few percentofallcore collapse supernovae,and m ay naturally explain som e ofthe brightest events ever seen (e.g.,SN 2005ap and SN 2008es) at L & 10 44 ergss 1 . Subjectheadings: radiativetransfer{ stars:neutron { supernovae:general{ supernovae:individual (SN 2005ap,SN 2008es,SN 2007bi)