Mildly relativistic X-ray transient 080109 and SN2008D: Towards a continuum from energetic GRB/XRF to ordinary Ibc SN

Understand

We analyze the hitherto available space-based X-ray data as well as ground-based optical data of the X-ray transient 080109/SN2008D.

• From the data we suggest that (i) The initial transient (\lesssim 800 sec) is attributed to the reverse shock emission of a mildly relativistic (\Gamma \sim a few) outflow stalled by the dense stellar wind.
• (ii) The subsequent X-ray afterglow (\lesssim 2\times 10^4 sec) can be ascribed to the forward shock emission of the outflow, with a kinetic energy \sim 10^{46} erg, when sweeping up the stellar wind medium.
• (iii) The late X-ray flattening (\gtrsim 2\times 10^4$ sec) is powered by the fastest non-decelerated component of SN2008D's ejecta.