(D. Svinkin, D. Frederiks, R. Aptekar, S. Golenetskii, М. Ulanov, A. Tsvetkova, A. Lysenko, A. Kozlova, T. Cline, and K. Hurley)
Ultra-long GRBs (with durationS >~1000 s) are a rare subclass of long GRBs; there are about a dozen known members to date with only a few bursts having extensive multiwavelength observations. The proposed causes of these ultra-long bursts include: core collapse of A blue supergiant (larger than those of normal long GRBs), low circumburst density which increases the ejecta deceleration time, and tidal disruption of a star by a massive black hole. In the simplest case, these bursts may represent the tail of the distribution of long GRBs. Konus-Wind (KW) is a gamma-ray all-sky spectrometer which has been successfully operating since November 1994. The Wind orbit is far from the Earth’s magnetosphere, which enables nearly uninterrupted observations of the entire sky under very stable background conditions. Therefore, KW offers powerful capabilities to observe ultra-long GRBs. We present the preliminary results of an extensive search for ultra-long GRBs in the Konus-Wind archival data covering 23 years of continuous observations from Nov 1994 to Aug 2017. We report temporal and spectral characteristics of a few dozen ultra-long GRB candidates, detected by KW and localized by the InterPlanetary Network. Finally, we discuss the connection between the events discovered and the KW long GRB sample.