3 Discussion

If the paucity of photons just below ${E_{\rm pk}}$ is due to synchrotron self-absorption, the magnetic energy density must be extremely high. From Rybicki & Lightman (1979, Eq. (6.53)) we find that

$$E_{\rm abs} = C(p)~\tau_{\rm T}^{\frac{2}{{\rm p}+4}}~ B^{\frac{{\rm p}+2}{{\rm p}+4}}$$ (2)

(also see Liang et al. 1997). For convenience, we calculate C(p) for appropriate values of p in Table 1. Assuming that $\Gamma \approx 1000$(making the co-moving ${E_{\rm abs}}\approx 70~\rm{eV}$), $\tau_{\rm T} \approx 1$ and using the Band et al. (1993) GRB function $\beta$ to give $p \approx 4$, we find that $B = 4 \ 10^{7}~{\rm G}$,which constrains some GRB models. Finally, we note that the BeppoSAX WFC data (2-40 keV) for this burst will be very useful in eliminating possible absorption mechanisms once they are released.

  

Table: Calculated values of C(p) for use with Eq. (2). See Rybicki & Lightman (1979) for details on calculating C(p)

Acknowledgements

AC thanks NASA-MSFC for his GSRP fellowship. This work is supported by NASA grant NAG5-3824.