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Astron. Astrophys. 323, 211-216 (1997)

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Dispersion measure variations observed in the direction of the millisecond pulsar PSR B1821-24

Ismaïl Cognard 1, 2 and Jean-François Lestrade 1

1 Observatoire de Paris, Sections of Meudon and Nançay, F-92195 Meudon Principal Cedex, France
2 LPCE-CNRS 3A, Avenue de la Recherche Scientifique, F-45071 Orleans Cedex 2, France

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 [FORMULA] 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  [FORMULA]  0.211, a result consistent with a Kolmogorov turbulent medium. The diffractive time scale [FORMULA] is also determined to be 50  [FORMULA]  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