Research On The Early Evolution Of Newborn Magnetars

Neutron star is a kind of astronomical object with high density and strong mag--netic field,and it provides an excellent target for people to study the properties of matter under the condition of high density and strong magnetic field.These special neutron stars with extremely strong magnetic field,rotating in millisecond-millisecond magnetar,has been considered to be closely related to astronomical phenomena such as gamma ray bursts,supernova,fast radio bursts,etc,and has become a hot research topic.At the same time,due to the rapid rotation and large magnetic deformation of millisecond magnetar,they may produce strong gravitational wave(GW)radiation in the frequency range of 100Hz to kilohertz,which is one of the key targets of the ground gravitational wave detector.As a possible origin,newborn millisecond magnetar can be born from the core collapse and supernova explosion of massive stars.Newborn magnetar can lose spin en-ergy through the way of magnetic dipole radiation and GW radiation caused by large magnetic deformation.Among them,the magnetic dipole radiation energy can be in-jected into the supernova remnant and because of the strong magnetic dipole radiation of newborn magnetar,present-day supernova remnants surrounding magnetar should be more energetic than those surrounding ordinary NSs.However,there is no signifi-cant difference between the two kinds of supernova remnant energy,that is to say,the total energy in remnants surrounding magnetar is no more thanEsn?1051erg.In this paper,based on the detailed discussion of the tilt angle,spin and thermal evo-lution in the early stage of the newborn magnetar,we calculate the magnetic dipole energy injected into the supernova remnant(Einj)by newborn magnetar.We con-sider the influence of viscosity and gravitational wave radiation on the evolution of the tilt angle in different evolution stages of the newborn magnetar,As for the spin and thermal evolution,we think that the spin-down of newborn magnetar is driven by magnetic dipole radiation and GW radiation and the star is cooled by modi-fied Urca reaction.Under the assumption that all the energy in supernova remnant is injected by magnetic dipole radiation(Esn=Einj),we can set a limit on these important physical parameters such as the toroidal magnetic field strength Bt and initial spin periods-Pi by using that energy in remnants surrounding magnetar is no more than1051 erg.The results show that Einj decreases with Pi increasing;when the toroidal magnetic field is strong enough and the gravitational wave radiation becomes important,Einj generally decreases with the increase of Bt.If the dipole magnetic field of the newborn magnetar Bd=1015G,when Pi?5.4ms,the toroidal magnetic field can satisfy the injected energyEinj<1051erg in the range of 1015?Bt?1017G.When Bd=1015G,Pi=4ms,then Bt=1017G can meet the observation limit.When Einj is constant,Pi decreases with increase of Bt.In addition,If Bd=1014G,the toroidal mag-netic field is 1014?Bt?1016G,in order to meet the observation limit,the lower limit of the initial rotation of the magnetar is Pi.It is also found that Einj is almost in-dependent of the free precession parameter n and the critical temperature Tc of the neutron superfluid.In this paper,the first chapter is an overview of neutron stars and magnetax,the second charpter introduces the evolution of newborn magnetar,the third chapter is our research work,that is using the supernova remnant energy observation surround-ing magnetar to limit the properties of newborn magnetar,the fourth chapter is a summary and prospect.