Abnormal scattering event in the direction to the pulsar B0834+06

Abstract

ABSTRACT Analysis of Space-VLBI observations of the pulsar B0834+06 conducted with RadioAstron at 324 MHz shows that in some cases one of the scattering screens could be located very close to the pulsar (about 10 pc from the pulsar), and it has a strong influence on the secondary spectra. For this case, the vertices of inverted arcs are aligned along the main parabolic arc and their width is inversely proportional to the scattering time. The shape of the main arc is determined by another scattering screen that is located at a distance of about 210 pc from the pulsar. The position of this screen is observed to be stable during 19 yr and its spatial scale is larger than 5.6 × 1015 cm. We found that the scattering disc may be approximated by an ellipse with a 2.5 axial ratio and with the position angle of the major axis of about −8○. A small-scale structure with a size of 0.1 au located at the close to observer screen and very high electron density of tens to a few thousand cm−3 for different models can be responsible for arclets in a secondary spectra. Additionally, angular refraction exists in the direction towards the pulsar. That suggests the presence of the cosmic prism. We have estimated the angle of refraction to be θref > 2 mas and the distance from prism to the observer D < 160 pc.