PSR J1825-0935 (PSR B1822-09) is a well-known young pulsar which shows interpulse (IP) emission. The mean pulse profile of PSR J1825-0935 consists of three main components: a strong and sharp main pulse (MP), a precursor (PC) preceding the MP by about 14.°5 of pulse phase, and a relatively weak IP leading the PC by about 159°. The most remarkable feature of PSR J1825-0935 is the peculiar and significant anticorrelation between the intensity of the IP and the PC. The IP is visible when the PC is weak or absent (i.e. in the Q-mode); on the other hand, the IP becomes very weak or undetectable when the PC is present (i.e. in the B-mode). Another curious property of PSR J1825-0935 is the periodic modulation in the Q-mode. Recently, researchers from the XAO pulsar group reported on high-sensitivity single-pulse observations of PSR J1825-0935 that were made using the Parkes 64-m radio telescope.

The researchers find that the periodic Q-mode modulation is in fact a periodic longitude-stationary intensity modulation occurring in the interpulse and the main pulse. The fluctuation spectral analysis showed that the modulation period is about 43P₁, where P₁ is the rotation period of the pulsar. Furthermore, they confirm that the modulation patterns in the interpulse and the main pulse are phase-locked. Specifically, the intensities of the interpulse and the immediately following main pulse are more highly correlated than for the main pulse and interpulse at any other lag. Polarization properties of the strong and weak Q-mode states are different, even for the trailing part of the main pulse which does not show the periodic intensity modulation.This work has been published by MNRAS (2019, 485, 3241).

A Q-mode single-pulse stack showing clearly the periodic modulation. The left- and right-hand panels show, respectively, the longitude range around the IP and the MP.