Limits on Turbulent HI Fluctuations Towards PSR B0329+54 On Scales Between 0.0025 and 12.5 AU

Abstract

We have measured the HI absorption towards pulsar B0329+54 using the Green Bank Telescope during 18 epochs between 2002 June 30 and 2003 October 10. Three observing epochs consisted of a continuous period of 20 hours each, while fifteen epochs were 1-2 hours each. We calculate the structure function of HI absorption variations toward the pulsar on time scales of 10 minutes to 16 months which, using the proper motion of 95 km/s and the parallactic distance of 1.03 kpc measured towards B0329+54 (Brisken et al. 2002), corresponds to angular scales of 0.37 micro-arcseconds to 23.8 milli-arseconds and samples structures between 0.0025-12.5 AU assuming HI gas half way to the pulsar and ignoring scintillation effects. We find no evidence for any turbulent HI absorption fluctuations towards B0329+54, with the following upper limits on the change in opacity for various absorption features: 0.026 at -31, -21, -18, and +4 km/s, 0.12 at -11 km/s, and 0.055 at -1 km/s.

Accepted to ApJ for 20 September, 2005 issue

References in corpus (5)

• VLBA Measurement of Nine Pulsar Parallaxes
• Southern Galactic Plane Survey Measurements of the Spatial Power Spectrum of Interstellar H I in the Inner Galaxy
• Multi-epoch HI line measurements of 4 southern pulsars
• Does tiny-scale atomic structure exist in the interstellar medium ?
• Small-Scale Variations of HI Spectra from Interstellar Scintillatio

Cited by in corpus (10)

• Science with ASKAP - the Australian Square Kilometre Array Pathfinder
• Atomic and Ionized Microstructures in the Diffuse Interstellar Medium
• Neutral Hydrogen Absorption Toward XTE J1810-197: the Distance to a Radio-Emitting Magnetar
• Arecibo Multi-Epoch HI Absorption Measurements Against Pulsars: Tiny-Scale Atomic Structure
• Tiny scale opacity fluctuations from VLBA, MERLIN and VLA observations of HI absorption toward 3C 138
• Small-scale structure traced by neutral hydrogen absorption in the direction of multiple-component radio continuum sources
• Detection of OH absorption against PSR B1718-35
• Tiny-scale Structure Discovered toward PSR B1557$-$50
• Tiny-Scale Properties within the Interstellar Medium towards PSR J1644$-$4559: I. Observational Evidence of Turbulence-induced Tiny Scale Atomic Structures
• H I absorption line and anomalous dispersion in the radio pulses of PSR B1937+21