  In 2000 September we observed a bright X-ray burst from X2127+119 with the
Rossi X-ray Timing Explorer. This burst has a multi-peaked profile, a peak
luminosity of ~6.5x10^{38} erg s^{-1}, a total integrated energy of ~2x10^{40}
ergs, and significant photospheric radius expansion to a maximum extent of
R=118+-5 km. From the luminosity-temperature relation during the expansion
phase we derive estimates for the gravitational redshift at the neutron star
surface, the corrected Eddington luminosity, and the neutron star mass. We
detect no slow (~30s) radial oscillations or fast (100-1200 Hz) coherent
oscillations or QPO during the burst.
  The 2000 September event is only the second burst ever observed from this
globular cluster binary (in M15 = NGC 7078), and it shares many characteristics
with the event detected by Ginga in 1988 October (Dotani et al. 1990; van
Paradijs et al. 1990), the key difference probably being the total amount of
material consumed in the thermonuclear flash.
