We report results on the timing and spectral analysis of observations of the millisecond pulsar PSR B1821 - 24 with RXTE , BeppoSAX and Chandra .
The X-ray light curve is characterized by two narrow peaks at a phase distance of 0.452 \pm 0.002 .
The average pulsed emission , over the range 1.6–20 keV , is well represented by a single power law with a photon index \alpha = 1.30 _ { +0.05 } ^ { -0.02 } 
and unabsorbed ( 2–10 keV ) pulsed X-ray flux of 3.9 \times 10 ^ { -13 } 
erg cm ^ { -2 } s ^ { -1 } .
We searched for a possible bunching of X-ray photons to verify if the X ray emission has a time structure similar to that of giant pulses and found a negative result .