tokens: neutrinos in spatial and temporal coincidences were reported by the IceCube neutrino telescope around this burst. A similar powerful burst GRB 130427A with energy of erg was detected by several satellites and ground-based telescopes (Ackermann et al. 2014 ; Maselli et al. 2014 ; Vestrand et al. 2014 ) and although searches for TeV–PeV neutrinos were performed, no excess were found above background. Gao et al. ( 2013b ) stated that the neutrino non-detection could constrain the values of the bulk Lorentz factor, emitting radius and the energy fraction converted into cosmic rays . They found that almost independently of the bulk Lorentz factor, the energy fraction between electrons and cosmic rays lies in the range . Although a robust analysis could be required, a simple proof can be done for GRB 160625B following a similar procedure. Form our results obtained in early afterglow can be seen that the energy fraction given to accelerate electrons and amplified the magnetic field at the end of the prompt phase is and , respectively. Taking into consideration the energy conservation condition , then the energy fraction converted into cosmic rays would be limited by . This result is very similar to that found by Gao et al. ( 2013b ) for GRB 130427A and might explain the lack of high-energy neutrinos around GRB 160625B. 7. Kann et al. ( 2010 ) studied the optical photometry data in a total of 42 GRB afterglows. They found that 10% of the afterglows presented optical peaks followed by a fast decay which are usually associated with a reverse-shock flash. Several authors have claimed that this kind of afterglow, as observed in GRB 080319B (Racusin et al. 2008 ), GRB 130427A (Ackermann et al. 2014 ; Vestrand et al. 2014 ), GRB 050904 (Kann et al. 2007 ), GRB 120711A (Martin-Carrillo et al. 2014 ), and GRB 990123 (Akerlof et al. 1999 ), among others, are only present in the most luminous bursts. Given that GRB 160625B has been one of the most powerful bursts detected which exhibited an optical flash with a fast decay, this burst seems to confirm this statement and belong in the same category. Table 2 Parameters found of the Early and Late Afterglow Table 3 Quantities Derived with our Leptonic Model for the Early and Late Afterglow Note. Quantities for the early afterglow are calculated at 150 s and for the late afterglow at . At the jet-break time ( s), the jet opening angle and the bulk Lorentz factor are and 6.9, respectively.) 5. Conclusions We have described the non-thermal multiwavelength observations of GRB 160625B collected with Fermi -LAT, Swift -XRT and several optical ground observatories. The multiwavelength observations of the early afterglow are consistent with the afterglow evolution in a stellar wind medium. The optical spectral index is consistent with the synchrotron radiation while GeV γ -ray flux with SSC emission dominated by the high latitude emission. In this event, a strong correlation between GeV γ -ray and optical fluxes
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