X-ray Flash ( XRF ) 100316D , a nearby super-long under-luminous burst with a peak energy E _ { p } \sim 20 keV , was detected by Swift and was found to be associated with an energetic supernova SN 2010bh .
Both the spectral and the temporal behavior are rather similar to XRF 060218 , except that the latter was associated with a “ less energetic ” SN 2006aj , and had a prominent soft thermal emission component in the spectrum .
We analyze the spectral and temporal properties of this burst , and interpret the prompt gamma-ray emission and the early X-ray plateau emission as synchrotron emission from a dissipating Poynting flux dominated outflow , probably powered by a magnetar with a spin period of P \sim 10 ms and the polar cap magnetic field B _ { p } \sim 3 \times 10 ^ { 15 } G. The energetic supernova SN 2010bh associated with this burst is however difficult to interpret within the slow magnetar model , and we suspect that the nascent magnetar may spin much faster with an initial rotation period \sim 1 ms .
It suggests a delay between the core collapse and the emergence of the relativistic magnetar wind from the star .
The diverse behaviors of low-luminosity GRBs and their associated SNe may be understood within a unified picture that invokes different initial powers of the central engine and different delay times between the core collapse and the emergence of the relativistic jet from the star .