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Ultra-long gamma ray bursts (ULGRBs) are a distinct class of GRBscharacterized by durations of several thousands of seconds, about two orders ofmagnitude longer than those of standard long GRBs (LGRBs). The driving engineof these events has not been uncovered yet, and ideas range from magnetars, totidal disruption events, to extended massive stars, such as blue super giants(BSG). BSGs, a possible endpoint of stellar evolution, are attractive for therelatively long free-fall times of their envelopes, allowing accretion to powera long-lasting central engine. At the same time, their large radial extensionposes a challenge to the emergence of a jet. Here we perform an end-to-endsimulation aimed at assessing the viability of BSGs as ULGRB progenitors. Theevolution to core collapse of a BSG star model is calculated with the MESAcode. We then compute the accretion rate for the fraction of envelope materialwith enough angular momentum to circularize and form an accretion disk, andinput the corresponding power into a jet which we evolve through the starenvelope with the FLASH code. Our simulation shows that the jet can emerge, andthe resulting light curves resemble those observed in ULGRBs, with durations$T_{90}$ ranging from $\approx$4000~s to $\approx10^4$ s depending on theviewing angle.

Ultra Long Gamma-Ray Bursts from the collapse of Blue Super Giant stars: an end-to-end simulation