  Observations of Type I X-ray bursts have long been taken as evidence that the
sources are neutron stars. Black body models approximate the spectral data and
imply a suddenly heated neutron star cooling over characteristic times of
seconds to minutes. The phenomena are convincingly explained in terms of
nuclear burning of accreted gas on neutron stars with low mass companion stars.
Prospects are promising that detailed theory and data from RXTE and future
missions will lead to better determinations of important physical parameters
(neutron star mass and radius, composition of the accreting gas, distance of
the source). Among the variety of bursts observed, there are probably
representatives of different kinds of explosive burning. RXTE's discovery of a
2.5 ms persistent coherent period from one Type I burster has now linked
bursters indisputably to the epitome of a neutron star, a fast spinning
magnetic compact object. Oscillations in some bursts had already been thought
to arise from the neutron stars' rotations. Detailed observations of these
oscillations are touchstones of how the explosive bursts originate and
progress, as well as independent measures of the neutron star parameters.
