Calderone, G.G.CalderoneGHIRLANDA, GiancarloGiancarloGHIRLANDAGHISELLINI, GabrieleGabrieleGHISELLINIBERNARDINI, Maria GraziaMaria GraziaBERNARDINICAMPANA, SergioSergioCAMPANACOVINO, StefanoStefanoCOVINOD'AVANZO, PaoloPaoloD'AVANZOD'Elia, V.V.D'EliaMELANDRI, AndreaAndreaMELANDRISALVATERRA, RubenRubenSALVATERRASBARUFATTI, BorisBorisSBARUFATTITAGLIAFERRI, GianpieroGianpieroTAGLIAFERRI2020-03-312020-03-3120150035-8711http://hdl.handle.net/20.500.12386/23725We gratefully acknowledge the referee for the useful comments and suggestions which greatly improved the paper. The research activity of AM, MGB and PD is supported by ASI grant INAF I/004/11/1. GC was supported by PRIN INAF 2011 (1.05.01.09.15).We compare the prompt intrinsic spectral properties of a sample of short gamma-ray bursts (GRBs) with the first 0.3 s (rest frame) of long GRBs observed by Fermi/GBM (Gamma Burst Monitor). We find that short GRBs and the first part of long GRBs lie on the same E<SUB>p</SUB>-E<SUB>iso</SUB> correlation, that is parallel to the relation for the time-averaged spectra of long GRBs. Moreover, they are indistinguishable in the E<SUB>p</SUB>-L<SUB>iso</SUB> plane. This suggests that the emission mechanism is the same for short and for the beginning of long events, and both short and long GRBs are very similar phenomena, occurring on different time-scales. If the central engine of a long GRB would stop after ̃0.3 × (1 + z) s, the resulting event would be spectrally indistinguishable from a short GRB.STAMPAenArticle10.1093/mnras/stu26642-s2.0-85015659077000350273500027https://academic.oup.com/mnras/article/448/1/403/9905502015MNRAS.448..403CFIS/05 - ASTRONOMIA E ASTROFISICA