2023ApJ...952...73M

The phenomenon of subpulse drifting is an important single-pulse phenomenon that can potentially provide important insights into the elusive radio emission mechanism in pulsars. We analyze the frequency behavior of the single pulses of B0818-41, observed from 300 to 500 MHz (Band 3 of the upgraded Giant Metrewave Radio Telescope, uGMRT), and compare it to the evolution of the average profile to place constraints on the geometry of the pulsar emission beam. We show that a circular carousel of discrete beamlets, where each beamlet is radially symmetric, is not consistent with the observed behavior, and we describe an alternative consistent range of possible elliptical carousel geometries. We also combine the uGMRT data with some archival Murchison Widefield Array observations and several other published profiles to characterize the profile evolution across a frequency range spanning ∼170 MHz to ∼1.4 GHz.