I present the data of the shell of classical Nova Persei ( 1901 ) obtained by the Advanced CCD Imaging Spectrometer S3 detector on-board Chandra Observatory .
The X-ray nebula is affected mostly by the complex interstellar medium around the nova and has not developed a regular shell .
The X-ray nebula is lumpy and asymmetric with bulk of emission coming from the southwestern quadrant .
The brightest X-ray emission is detected as an arc that covers from the west to the south of the central source .
Part of this feature , which is co-spatial with the brightest non-thermal radio emission region , is found to be a source of non-thermal ( synchrotron ) X-ray emission with a power law photon index of 2.3 ^ { +1.5 } _ { -0.9 } and \alpha =0.68 ^ { +0.03 } _ { -0.15 } at about a flux of 1.7 \times 10 ^ { -13 } erg cm ^ { -2 } s ^ { -1 } .
This confirms that the shell is a cite of particle acceleration , mainly in the reverse shock zone .
There are strong indications for nonlinear diffusive shock acceleration occurring in the forward shock/transition zone with an upper limit on the non-thermal X-ray flux of 1.0 \times 10 ^ { -14 } erg cm ^ { -2 } s ^ { -1 } .
The total X-ray spectrum of the nebula consists of two prominent components of emission ( other than the resolved synchrotron X-ray emission ) .
The component dominant below 2 keV is most likely a non-equilibrium ionization thermal plasma of kT _ { s } =0.1-0.3 keV with an X-ray flux of 1.6 \times 10 ^ { -11 } erg cm ^ { -2 } s ^ { -1 } .
There is also a higher temperature , kT _ { s } =0.5-2.6 keV , embedded , N _ { H } = ( 4.0-22.0 ) \times 10 ^ { 22 } cm ^ { -2 } , emission component prominent above 2 keV .
The unabsorbed X-ray flux from this component is 1.5 \times 10 ^ { -10 } erg cm ^ { -2 } s ^ { -1 } .
The X-ray emitting plasma is of solar composition except for enhancement in the elemental abundances ( mean abundances over the remnant ) of Ne/Ne _ { \odot } and N/N _ { \odot } in a range 13-21 and 1-5 , respectively .
A distinct emission line of neon , He-like Ne IX , is detected which reveals a distribution of several emission knots/blobs and shows a cone-like structure with wings extending toward NW and SE at expansion velocities about 2600 km s ^ { -1 } in the X-ray wavelengths .

The emission measures yield an average electron density in a range 0.6-11.2 cm ^ { -3 } for both of the components ( filling factor=1 ) .
The electron density increases to higher values \sim 300 cm ^ { -3 } if the filling factor is decreased substantially .
The mass in the X-ray emitting nebula is ( 2.1-38.5 ) \times 10 ^ { -4 } M _ { \odot } .
The X-ray luminosity of the forward shock \sim 4.3 \times 10 ^ { 32 } erg s ^ { -1 } indicates that it is adiabatic .
The shocked mass , the X-ray luminosity and comparisons with other wavelengths suggest that the remnant has started cooling and most likely is in a Sedov phase .