Gigahertz-peaked spectra pulsars and thermal absorption model

Abstract

We present the results of our radio interferometric observations of pulsars at 325 MHz and 610 MHz using the Giant Metrewave Radio Telescope (GMRT). We used the imaging method to estimate the flux densities of several pulsars at these radio frequencies. The analysis of the shapes of the pulsar spectra allowed us to identify five new gigahertz-peaked spectra (GPS) pulsars. Using the hypothesis that the spectral turnovers are caused by thermal free-free absorption in the interstellar medium, we modeled the spectra of all known objects of this kind. Using the model, we were able to put some observational constrains on the physical parameters of the absorbing matter, which allows us to distinguish between the possible sources of absorption. We also discuss the possible effects of the existence of GPS pulsars on future search surveys, showing that the optimal frequency range for finding such objects would be from a few GHz (for regular GPS sources) to possibly 10 GHz for pulsars and radio-magnetars exhibiting very strong absorption.

Accepted for publication in ApJ, 28 pages, 8 figures

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• Multi-frequency radio observations of the radio-loud magnetar XTE J1810-197
• Flux density measurements for 32 pulsars in the 20 cm band
• Multi-frequency observations and spectral analysis of two gigahertz-peaked spectra pulsars
• The significance of low frequency interferometric observations for the GPS pulsar flux estimation: the case of J1740+1000
• The uGMRT observations of three new GPS pulsars
• Modelling the thermal absorption and radio spectra of the binary pulsar B1259-63
• Structural and spectral properties of Galactic plane variable radio sources
• Beyond the Simple Power Law: A Bayesian Analysis of 897 Pulsar Spectra
• The Low-Frequency Spectra of Radio Pulsars