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We analyze gamma-ray bursts (GRBs) detected by \textit{Fermi}/Gamma-Ray BurstMonitor (GBM) and having single pulse. We fit the light curves with a modelhaving exponential rise and decay parts. We perform a detailed time-resolvedspectroscopy using four models: Band, blackbody with a power-law (BBPL),multicolour blackbody with a power-law (mBBPL) and two blackbodies with apower-law (2BBPL). We find that models other than the BBPL give better$\chi_{red}^2$ for the "hard-to-soft" (HTS) pulses, while for the "intensitytracking" (IT) pulses, the BBPL model is statistically as good as the othermodels. Interestingly, the energy at the peak of the spectrum resulting fromthe BBPL model ($\sim3kT$), is always lower than that of the $\nu F_{\nu}$spectrum of the Band function. The values of the low energy photon index($\alpha$) of the Band function are often higher than the fundamental singleparticle synchrotron limit, especially for the HTS pulses. Specifically we findtwo extreme cases --- for GRB~110817A (HTS GRB) $\alpha$ is always higher,while for GRB~100528A (IT GRB) $\alpha$ is always within the synchrotronregime. The PL component of the BBPL model always starts with a delay comparedto the BB component, and it lingers at the later part of the prompt emissionphase. For three HTS GRBs, namely, GRB~081224, GRB~100707A and GRB~110721A thisbehaviour is particularly significant and interestingly there are reported LATdetections for them. Finally, we argue that various evidences hint that neitherBBPL nor Band model is acceptable, while 2BBPL and mBBPL are the mostacceptable models for the set of GRBs we have analyzed.

Time-resolved Spectral Study Of Fermi GRBs Having Single Pulses