AnXMM‐NewtonObservation during the 2000 Outburst of SAX J1808.4−3658

I present a XMM-Newton observation of the accretion driven millisecond X-raypulsar SAX J1808.4-3658 during its 2000 outburst. The source was conclusivelydetected, albeit at a level of only ~2 x 10^{32} erg/s. The source spectrumcould be fitted with a power-law model (with a photon index of ~2.2), a neutronstar atmosphere model (with a temperature of ~0.2 keV), or with a combinationof a thermal (either a black-body or an atmosphere model) and a power-lawcomponent. During a XMM-Newton observation taken approximately one year later,the source was in quiescence and its luminosity was a factor of ~4 lower. It ispossible that the source spectrum during the 2000 outburst was softer than itsquiescent 2001 spectrum, however, the statistics of the data do not allow tomake a firm conclusion. The results obtained are discussed in the context ofthe 2000 outburst of SAX J1808.4-3658 and the quiescent properties of thesource.Comment: Accepted for publication in ApJ, 15 January 200