Jiamusi pulsar observations: IV. The core-weak pattern of PSR B0329+54

TL;DR

This paper reports the discovery of a new core-weak emission mode in pulsar PSR B0329+54, characterized by periodic profile component variations and phase shifts, based on long-term observations at 2250 MHz.

Contribution

It identifies and characterizes a novel core-weak mode in PSR B0329+54, revealing regular patterning in pulse profile component variations over multiple periods.

Findings

The core-weak mode lasts for several periods.

Profile components show correlated intensity and phase variations.

The mode involves a systematic drift of the core component out of the normal emission window.

Abstract

The bright pulsar PSR B0329+54 was previously known for many years to have two emission modes. Sensitive observations of individual pulses reveal that the central component of pulse profile, which is called core component, is found to be very weakened occasionally for some periods and then recovered. This is the newly identified core-weak mode. Based on our long observations of PSR B0329+54 by the Jiamusi 66-m telescope at 2250 MHz, we report here that the profile components of individual pulses, including these for the core and the leading and trailing peaks, are relatedly varying over some periods even before and after the core-weak mode, forming a regular pattern in the phase-vs-time plot for a train of period-folded pulses. The pattern has a similar structure for the core-weak mode with a time scale of 3 to 14 periods. It starts with an intensity brightening at the trailing phase of the core component, and then the core intensity declines to a very low level, as if the core component is drifting out from the normal radiation window within one or two periods. Then the intensity for the trailing components is enhanced, and then the leading component appears at an advanced phase. Such a core-weak mode lasts for several periods. Finally, the core-weak mode ends up with an enhanced intensity at the leading phase for the core component, as if the core gradually comes back and finally stays at the phase of the profile center as it used to.