We report the results of the Chandra ACIS-S observations of the elliptical galaxy NGCÂ 821 , which harbors a supermassive nuclear black hole ( of 3.5 \times 10 ^ { 7 } M _ { \odot } ) , but does not show sign of AGN activity .
A small , 8.5 ^ { \prime \prime } long ( \sim 1 Â kpc at the galaxy ’ s distance of 23Â Mpc ) , S-shaped , jet-like feature centered on the nucleus is detected in the 38Â ksec ACIS-S integrated exposure of this region .
The luminosity of this feature is L _ { X } \sim 2.6 \times 10 ^ { 39 } ergs~ { } s ^ { -1 } ( 0.3-10Â keV ) , and its spectrum is hard ( described by a power-law of \Gamma = 1.8 ^ { +0.7 } _ { -0.6 } ; or by thermal emission with kT > 2 Â keV ) .
We discuss two possibilities for the origin of this feature : ( 1 ) a low-luminosity X-ray jet , or ( 2 ) a hot shocked gas .
In either case , it is a clear indication of nuclear activity , detectable only in the X-ray band .
Steady spherical accretion of the mass losses from the central stellar cusp within the accretion radius , when coupled to a high radiative efficiency , already provides a power source exceeding the observed radiative losses from the nuclear region .