Statistical Properties Of Fast Blue Optical Transients And Their Radio Afterglows In The Magnetar Engine Model

Fast blue optical transients（FBOTs）are a type of optical transient source with rapid radiation evolution（usually rising within ten days）and high radiation luminosity.Their spectra typically show no distinctive spectral lines,but rather a predominantly blue continuum.The origin and eruption mechanism of FBOTs are currently unclear,with two main theoretical models being the shock interaction model and the central energy model.The former usually requires the precursor star to be in a relatively dense environment,while the latter usually assumes that the explosion produced a rapidly rotating,highly magnetized neutron star（magnetar）.Since the energy output behavior of magnetar energy is often highly consistent with the observed light curve,and the energy source mechanism is often used to explain long gamma-ray bursts and superluminous supernova,and other related phenomena,this paper will mainly study the FBOT phenomenon based on the magnetar model.First,based on 40 FBOTs collected from several optical transient surveys,we use the magnetar energy model to fit their multi-band light curve and obtain the constraints on the magnetar’s magnetic field intensity B,initial rotation period P_i,ejecta mass M_ej,and other key model parameters.Specifically,we found that the ejected mass of FBOTs should generally be less than 1 M_⊙,with a median value of only 0.11M_⊙.The corresponding ranges for the magnetar’s initial rotation period and magnetic field intensity were 9.1_-4⁺⁹..₄³ms and 11_-7⁺¹⁸×10¹⁴G,respectively.Second,we compared and analyzed the parameter distributions of FBOTs,SLSNe,l GRBs,and broad-line Type Ic supernovae,finding that their distribution in the corresponding parameter space presents the characteristics of continuous transition,but does not show an independent aggregation state.In particular,there was a significant anti-correlation between P_iand M_ej:P_i∝M_ej^-0.41.These results suggest that these eruptive phenomena may have a unified origin mechanism.Therefore,given that SLSN and l GRB are both the results of massive star eruptions,we can basically infer that FBOT also originates from stellar eruptions,but its progenitor has a relatively small mass.In other words,FBOTs are likely the result of supernova eruptions from stars that have undergone extreme stripping,and their successful eruption may be due to being in a binary star system.The assumption of a binary star for the progenitor is also helpful in understanding the reasons for the P_i-M_ejcorrelation and the special nature of SLSNe and l GRBs.Third,considering that different FBOT models require different progenitor properties and stellar circumstellar environments,exploring the stellar circumstellar environment can help to constrain the progenitor’s mass loss rate and distinguish between different models.Therefore,we calculated the radio afterglow radiation caused by the interaction between FBOT’s ejecta and the surrounding medium.Based on the parameter distribution obtained from the optical fitting,we predicted the distribution of FBOT radio（8.4 GHz）afterglow peak time and peak luminosity,which are mainly as follows t_peak,ν=10^2.12±0.63days and L_peak,ν=10^28.73±0.83erg s^-1Hz^-1.Based on these results,the joint observation rate of FBOTs and their radio afterglows by ZTF and VLA within the redshift range of z≤1 is approximately 8.7%,and this rate can be increased to 23.9%by future joint detection by CSST and SKA1.