The Energy Sources Of Superluminous Supernovae And Luminous Gamma-ray Burst-Supernovae

Supernovae(SNe)are the most brilliant optical stellar-class explosions.In the last decade,several optical transient search projects discovered dozens of so-called superluminous super-novae(SLSNe)whose peak luminosities and radiated energy are(?)7×1043 erg s-1 and(?)1051 erg,at least an order of magnitude larger than that of normal SNe.According to their optical spectrum features,SLSN types can be split into two broad categories of type I that are hydrogen-deficient and type II that are hydrogen-rich.Investigating and determining the energy sources of SLSNe would be of outstanding importance for understanding the stellar evolution and ex-plosion mechanisms.The energy sources of SLSNe can be determined by analyzing their light curves(LCs)and spectra.This paper aim to explore these important issues.In chapter 1,we summarize the observation history,classification scheme,progenitors,and the evolution of the concept of SNe.In chapter 2,we present the most prevailing models accounting for the LCs of SLSNe,the 56Ni cascade decay model,the magnetar spin-down model,the ejecta-CSM interaction model,the jet-ejecta interaction model and their different combinations.In chapter 3,we construct a triple energy-source model to explain the light curve of iPT-F13ehe.that challenges all single energy-source models,because the spectral analysis shows that?2.5M(?)of 56Ni have been synthesized but are inadequate to power the peak bolomet-ric emission of iPTF13ehe,while the rebrightening of the late-time LC and the H? emission lines indicate that the ejecta-CSM interaction must play a key role in powering the late-time LC.Here we propose a triple-energy-source model,in which a magnetar together with some amount((?)2.5M(?))of 56Ni may power the early LC of iPTF13ehe while the late-time rebrightening can be quantitatively explained by an ejecta-CSM interaction.Furthermore,we suggest that iPTF13ehe is a genuine core-collapse supernova rather than a pulsational pair-instability super-nova candidate.Further studies on similar SLSNe in the future would eventually shed light on their explosion and energy-source mechanisms.In chapter 4,we study the most luminous known SN associated with a gamma-ray burst(GRB),SN 2011kl.The photospheric velocity of SN 201 lkl around peak brightness is 21,000±7000 km s-1.Owing to different assumptions related to the LC evolution(broken or unbroken power-law function)of the optical afterglow of GRB 111209A,different techniques for the LC decomposition,and different methods(with or without a near-infrared contribution),three groups derived three different bolometric LCs for SN 2011kl.Previous studies have shown that the LCs without an early-time excess preferred a magnetar model,a magnetar+56Ni model,or a white dwarf tidal disruption event model rather than the radioactive heating model.On the other hand,the LC shows an early-time excess and dip that cannot be reproduced by the aforementioned models,and hence the blue-supergiant model was proposed to explain it.Here,we reinvestigate the energy sources powering SN 201 lkl.We find that the two LCs without the early-time excess of SN 2011kl can be explained by the magnetar+56Ni model,and the LC showing the early excess can be explained by the magnetar+56Ni model taking into account the cooling emission from the shock-heated envelope of the SN progenitor,demonstrating that this SN might primarily be powered by a nascent magnetar.In chapter 5,we study a nearby(z = 0.023146)luminous Ic supernova SN 2007D that have narrow LC and high peak luminosity.Previous research based on the assumption that it was powered by 56Ni cascade decay suggested that the inferred 56Ni mass and the ejecta mass are?1.5M(?)and?3.5M(?),respectively.In this chapter,we employ some multi-band LC models to model the R-band and the color(V-R)evolution LCs of SN 2007D and investigate the possible energy sources powering them.We find that the pure 56Ni model is disfavored and the muiti-band LCs of SN 2007D can be reproduced by a combination of 0-0.2 M(?)of 56Ni and a magnetar whose initial rotational period P0 and the magnetic field strength Bp are?7.5 ms and?4 x 1014 G,respectively.By fitting the multi-band LCs,we find that the theoretical U-band peak absolute magnitude(MU,peak)is<-21 mag,indicating that SN 2007D may be the nearest type I SLSN to date.We caution that,however,the extinction values are rather uncertain.If smaller extinction values are adopted,the peak magnitudes of the multi-band LCs would be?0.4 mag dimmer.In this case,SN 2007D might be a luminous SN like several luminous "gap-filler" optical transients which bridge ordinary SNe and SLSNe rather than a SLSN.We summarize our results and give a brief look into the future in chapter 6.