Multifaced Emission Variability of Pulsar J0846–3533: Periodic Amplitude Modulation, Mode Switching, and Pulse Nulling

Full polarization-product data (corresponding to the four Stokes parameters) were processed in real time using the “Medusa” graphics processing unit (GPU) cluster, then recorded to disk in PSRFITS search-mode format (A. W. Hotan et al. 2004) with 8-bit quantization. The time resolution of the observations was set to 64 μs. However, owing to the absence of data from a stable reference flux calibrator and observations of a 100% linearly polarized reference signal (a linearly polarized noise diode signal with amplitude modulation), which are typically acquired prior to and subsequent to each target observation, the flux density and polarization of the pulsar have not been calibrated.

Prior to scientific analysis, a comprehensive offline data reduction pipeline was implemented using the DSPSR5 (W. van Straten & M. Bailes 2011) and PSRCHIVE6 (A. W. Hotan et al. 2004) software packages. Initial steps focused on mitigating radio frequency interference (RFI): frequency channels at sub-band boundaries were zero-weighted to account for bandpass roll-off, and RFI-contaminated channels were identified and flagged using a median-filtering technique applied across both frequency and time domains.

Subsequently, the data were incoherently dedispersed at the pulsar’s dispersion measure (DM=94.155 pc cm−3) to correct for frequencydependent smearing induced by the interstellar plasma. Finally, using the pulsar’s rotational ephemerides from the ATNF pulsar catalog (R. N. Manchester et al. 2005), the data were resampled and folded at the topocentric spin period to generate a twodimensional pulse stack with 1024 longitude bins.

The resulting dataset, free of RFI, provided the foundation for all subsequent analyses of single-pulse variability, mode switching, nulling, and fluctuation spectra.