Tidal Disruption Events And High Energy Neutrino Background

Tidal Disruption Event(TDE)refers to high energy flares induced by accretion of debris of a star by massive black hole when the star is tidally disrupted once it close enough to the massive black hole.TDEs was first proposed to be a indicator of the existence of massive black hole in quiescent galaxies.TDEs’ energy spectrum,light variation characteristics,and event occurrence rates allow us to spy on the mass of black holes in the center of galaxies,detailed accretion processes,the mechanism and efficiency of generation of jet or outflow,and the distribution of stars and media in the centra galactic area.The number of TDEs that have been discovered so far is less than one hundred,and only a few of them show relativistic jet structures.With the development of time-domain astronomy with a large field of view,high sensitivity,and high-efficiency survey,the number of TDEs will increase statistically.As an extremely energetic phenomenon in high-energy astrophysics,TDEs are also regarded as the source of ultra-high-energy cosmic rays,especially jet-launched TDEs.The corresponding high-energy neutrinos produced in jetted-TDEs may contribute to the flux of high-energy neutrino background observed by IceCube.In this thesis,we will derive constraints on the mass function of black holes and the efficiency of jet generation in TDEs assuming that high-energy neutrino background are produced by all the jetted-TDEs along the line of sight.The first chapter introduces the research background,including black holes and black hole mass function,observation and research status of TDEs,as well as highenergy neutrino background.In the first part of these,we introduce the classification of the black hole and the formation mechanism of the massive black holes,and point out that the important of observational and theoretical studies of intermediate mass black hole,further presents the research progress of the black hole mass function in recent years.In the second part,we introduce that the basic dynamics and light features of TDEs,as well as light curve impact factors;that features,formation mechanism and observation status of jet TDEs,and their proportional distribution under the limitation of current observation;that multi-wavelength observations and properties of TDE from X-ray to radio.In the last part,we briefly introduce the high-energy neutrino formation channels and background,as well as the relation between high-energy cosmic ray and high-energy neutrino.The second chapter is the main subject of this thesis.By parameterizing the properties of the jetted-TDE SW J1644+57,we have established a theoretical model of the jetted-TDEs and calculated the high-energy neutrino spectrum generated by a single jetted TDE.We then provide the neutrino flux from all possible jetted-TDEs based on the black hole mass function in local universe.Generally,the maximum black hole mass in the integration of the black hole mass function can be taken as 107.5M⊙.However,the lower limit of the black hole mass allowed in the black hole mass function has no theoretical constraints.Therefore,we take Mmin and the parameters related to the efficiency of the jet formation in TDEs(η0 与α)as free parameters,and use the least chi-square analysis method to fit the IceCube HESE high energy neutrino background.Our results show that if the high-energy neutrino background is used as the upper limit of the neutrinos contributed by all jetted-TDEs,Mmin is 1.33 ×104M⊙,and the jet fraction becomes higher with decreasing of the black hole mass.We summarize our main results and discuss the some possible follow-up research work in the last chapter.