  The X-ray emission from the young supernova remnant (SNR) N103B is measured
and analysed using the high-resolution cameras and spectrometers on board XMMM
and CHANDRA. The spectrum from the entire remnant is reproduced very well with
three plasma components of kT=0.55, 0.65, and 3.5 keV, corresponding roughly to
line emission by the O-K, Fe-L, and Fe-K species, respectively. Narrow band
images reveal different morphologies for each component. The kT=0.65keV
component, which dominates the emission measure (4.5E65m^{-3}), is in
ionisation equilibrium. This provides a lower limit of 3000 yrs to the age of
the remnant, which is considerably older than the previously assumed age of the
remnant (1500 yrs). Based on the measured energy of the Fe-K feature at 6.5
keV, the hot (3.5 keV) component is found to be recently shocked (~200 yrs) and
still ionising. The high elemental abundances of O and Ne and the low abundance
of Fe could imply that SNR N103B originated from a type II supernova (SN)
rather than a type Ia SN as previously thought.
