Meterwavelength Single-pulse Polarimetric Emission Survey. V. Flux Density, Component Spectral Variation, and Emission States

• Published in: The Astrophysical journal Vol. 917; no. 1; pp. 48 - 72
• Main Authors: Basu, Rahul, Mitra, Dipanjan, Melikidze, George I.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-08-2021; IOP Publishing
• Subjects: Astrophysics; Cones; Emission analysis; Emission measurements; Fluctuations; Flux density; Frequency ranges; Polarimetry; Polls & surveys; Pulsars; Radio emission; Radio pulsars; Spectra
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac0828

Abstract
We present the flux density measurements of the pulsars observed in the Meterwavelength Single-pulse Polarimetric Emission Survey. The average flux densities were estimated in 113 pulsars at two frequencies of 325 and 610 MHz using interferometric imaging. The average profile and single-pulse emission in each pulsar were calibrated using the estimated flux density. We have used the flux-calibrated average profile to study the variation of the spectral index across the emission beam in 21 pulsars where the core, inner cone, and the outer conal components could be clearly identified. The central core component showed a steeper increase in emission at the lower frequency compared with conal emission, with an average difference in spectral index
δα
core-cone
∼ −0.7 between the core and the conal components in this frequency range. In contrast, the inner conal components had positive difference in their spectral index compared to the outer cones with average difference
δα
in-out
∼ +0.3. The variation in the spectral index across the pulse window should provide valuable inputs for constraining the radio emission processes. The single-pulse emission showed the presence of emission mode changing in 12 pulsars, with three cases where the phenomenon is being reported for the first time. In addition, we have also detected enhanced emission for short durations or flaring, in parts or across the entire emission window in 14 pulsars. The sudden changes in the emission during mode changing, as well as these bursting states, are unrelated to the emission mechanism and suggest the presence of rapid and repetitive changes during the plasma generation process.