Magnetar central engine powering the energetic GRB 210610B ?

Abstract

The bright GRB 210610B was discovered simultaneously by Fermi and Swift missions at redshift 1.13. We utilized broadband Fermi-GBM observations to perform a detailed prompt emission spectral analysis and to understand the radiation physics of the burst. Our analysis displayed that the low energy spectral index ($\alpha_{\rm pt}$) exceeds boundaries expected from the typical synchrotron emission spectrum (-1.5,-0.67), suggesting additional emission signature. We added an additional thermal model with the typical Band or CPL function and found that CPL + BB function is better fitting to the data, suggesting a hybrid jet composition for the burst. Further, we found that the beaming corrected energy (E$_{\rm \gamma, \theta_{j}}$ = 1.06 $\times$ 10$^{51}$ erg) of the burst is less than the total energy budget of the magnetar. Additionally, the X-ray afterglow light curve of this burst exhibits achromatic plateaus, adding another layer of complexity to the explosion's behavior. Interestingly, we noted that the X-ray energy release during the plateau phase (E$_{\rm X,iso}$ = 1.94 $\times$ 10$^{51}$ erg) is also less than the total energy budget of the magnetar. Our results indicate the possibility that a magnetar could be the central engine for this burst.