Dispersion Smearing Research Articles

Deep radio observations of the rich globular clusters Terzan 5 and Liller 1

We have obtained deep 6, 20 and 90 cm observation of two of the richest globular clusters in the galaxy, Terzan 5 and Liller 1. In addition to the well known eclipsing pulsar, PSR1744-24A, our 20 cm image of Terzan 5 displays numerous point sources within 30″, or 4 core radii of the cluster center. The density of these objects rises rapidly toward the core, where an elongated region of emission is found. This feature may be due to the presence of a higher density of point sources than can be resolved by the 1″ resolution of our data. Observations at 6 and 90 cm show that the brightest individual sources, as well as the extended emission, possess the steep spectra expected of pulsars. Furthermore, we find that the strength of the sources in the 20 cm image agrees well with the standard pulsar luminosity function. The total luminosity and number of objects observed in Terzan 5 suggest that this cluster may contain 100 pulsars — probably more than any other Galactic cluster. Although we do not resolve individual sources in Liller 1, comparison of our images with other observations suggests that we are again observing the sum of emission from a number of objects. The 90 cm flux densities of Terzan 5 and Liller 1 are 35 and 9 mJy, respectively, implying that a number of bright pulsars in these clusters have been hidden from pulsed searches, perhaps by a combination of dispersion smearing, scattering and doppler broadening.

Smearing of a Kick While Being Displaced From a Well

Well control operations while drilling with an oil-base mud can suffer several unexpected phenomena. One of these is the dispersion (smearing) of the gas in solution whenever a gas kick is being circulated from the well. If the gas influx has gone into solution, it is very important to predict the movement of this gas-contaminated mud as it is circulated from the well. A computer model of non-Newtonian fluids flowing in an annulus of any eccentricity has been developed with which to accurately model this dispersion. The movement of the gas-contaminated mud is predicted as a consequence of the velocity profiles established as the displacement of the annulus progresses.