Since the discovery of the accreting millisecond pulsar XTE J1814-338 a total of 27 thermonuclear bursts have been observed from the source with the Proportional Counter Array ( PCA ) onboard the Rossi X-ray Timing Explorer ( RXTE ) .
Spectroscopy of the bursts , as well as the presence of continuous burst oscillations , suggests that all but one of the bursts are sub-Eddington .
The remaining burst has the largest peak bolometric flux of 2.64 \times 10 ^ { -8 } erg s ^ { -1 } cm ^ { -2 } , as well as a gap in the burst oscillations , similar to that seen in Eddington limited bursts from other sources .
Assuming this burst was Eddington limited we obtain a source distance of \approx 8 kpc .
All the bursts show coherent oscillations at the 314.4 Hz spin frequency .
The burst oscillations are strongly frequency and phase locked to the persistent pulsations .
Only two bursts show evidence for frequency drift in the first few seconds following burst onset .
In both cases the initial drift corresponds to a spin down of a few tenths of a Hz .
The large oscillation amplitude during the bursts confirms that the burst flux is modulated at the spin frequency .
We detect , for the first time , a significant first harmonic component in burst oscillations .
The ratio of countrate in the first harmonic to that in the fundamental can be > 0.25 and is , on average , less than that of the persistent pulsations .
If the pulsations result from a single bright region on the surface , the harmonic strength suggests the burst emission is beamed , perhaps due to a stronger magnetic field than in non-pulsing LMXBs .
Alternatively , the harmonic content could result from a geometry with two bright regions .