Context : GRB 110709B is the first source for which Swift BAT triggered twice , with a time separation of \sim 10 minutes .
The first emission ( Episode 1 ) goes from 40 s before the first trigger up to 60 s after it .
The second emission ( Episode 2 ) goes from 35 s before the second trigger to 100 s after it .
[ … ] Within the Induced Gravitational Collapse ( IGC ) model , we assume the progenitor to be a close binary system composed of a core of an evolved star and a Neutron Star ( NS ) .
The evolved star explodes as a Supernova ( SN ) and ejects material that is partially accreted by the NS .
We identify this process with Episode 1 .
The accretion process brings the NS over its critical mass , thus gravitationally collapsing to a BH .
This process leads to the GRB emission , Episode 2 .
[ … ]

Aims : We analyze the spectra and time variability of Episode 1 and 2 and compute the relevant parameters of the binary progenitor and the astrophysical parameters both in the SN and the GRB phase in the IGC paradigm .

Methods : We perform a time-resolved spectral analysis of Episode 1 by fitting the spectrum with a blackbody ( BB ) plus a power-law ( PL ) spectral model .
We analyze Episode 2 within the Fireshell model , identifying the Proper-GRB ( P-GRB ) and simulating the light curve and spectrum .
We establish the redshift to be z = 0.75 , following the phenomenological methods by Amati , by Yonetoku and by Grupe , and our analysis of the late X-ray afterglow [ … ] .

Results : We find for Episode 1 a temperature of the BB component that evolves with time following a broken PL , with the slope of the PL at early and late times times \alpha = 0 and \beta = -4 \pm 2 , respectively .
The break occurs at t = 41.21 s. The total energy of Episode 1 is E _ { iso } ^ { ( 1 ) } = 1.42 \times 10 ^ { 53 } erg .
The total energy of Episode 2 is E _ { iso } ^ { ( 2 ) } = 2.43 \times 10 ^ { 52 } erg .
We find at transparency a Lorentz factor \Gamma \sim 1.73 \times 10 ^ { 2 } , laboratory radius of 6.04 \times 10 ^ { 13 } cm , P-GRB observed temperature kT _ { P - GRB } = 12.36 keV , baryon load B = 5.7 \times 10 ^ { -3 } and P-GRB energy of E _ { P - GRB } = 3.44 \times 10 ^ { 50 } erg .
[ … ]

Conclusions : We interpret GRB 110709B as a member of the IGC sources , together with GRB 970828 , GRB 090618 and GRB 101023 .
The existence of the XRT data during the prompt phase of the emission of GRB 110709B ( Episode 2 ) offers an unprecedented tool for improving the diagnostic of GRBs emission .