The first outburst of SAX J1808.4-3658 revisited

Data of the 1996 outburst of the single-known accreting millisecond pulsar SAX J1808.4-3658, taken with the Wide Field Cameras (WFCs) on BeppoSAX, are revisited with more complete data coverage and more comprehensive analysis techniques than in a previous report. An additional type-I X-ray burst was identified which occurred at a time when the persistent emission is below the detection limit, roughly 30 days after outburst maximum. This burst is three times longer than the first two bursts, and 50% brighter. It is the b rightest burst within the similar to 1700 type-I bursts detected so far wit h the WFCs. A spectral analysis of the data reveals a distance to SAX J1808 .4-3658 of similar to2.5 kpc. This is an update from a previously reported value of 4 kpc. We present the evidence that we have for the presence of os cillations at the pulsar frequency during part of the newly found burst. Su ch an oscillation would lend support to the idea that the frequency of mill isecond burst oscillations in other objects is very close to the neutron st ar rotation frequency.