Dispersion measure variations observed in the direction of the millisecond pulsar PSR B1821-24
Ismaïl Cognard 1, 2 and
Jean-François Lestrade 1
Received 2 April 1996 / Accepted 18 December 1996
High-precision timing observations of the millisecond pulsar PSR B1821-24 have been conducted at the Nançay radiotelescope between 1.37 GHz and 1.7 GHz since January 22, 1992 until January 10, 1996. This dense and precise multi-frequency timing series has allowed secular variations of the dispersion measure as high as 0.005 pc.cm-3 /year in the direction of this pulsar to be determined. The index of the power-law spatial spectrum of the electron density fluctuations has been determined for the first time in the direction of this pulsar and is 3.727 0.211, a result consistent with a Kolmogorov turbulent medium. The diffractive time scale is also determined to be 50 s and is relatively consistent with the determination based on the space velocity of PSR B1821-24. We also provide a new proper motion for this pulsar for which the declination component is for the first time inconsistent with zero.
Key words: pulsars: general pulsars: individual: PSR B1821-24 ISM: general stars: kinematics
© European Southern Observatory (ESO) 1997
Online publication: June 5, 1998