Abstract <p>An analysis of observations of the pulsar B1237+25 at a frequency of 111 MHz has been presented. The observations have been carried out with the Large In-Phase Antenna (LPA) of the Pushchino Radio Astronomical Observatory, Lebedev Physical Institute. A new component in the average profile in the central region of the emission has been detected. This component with a half-width of 1.6 ms has been observed against the background of a more extended component with a half-width of 7 ms. This new component of the average profile at a frequency of 111 MHz manifests itself in all modes of the pulsar radio emission: quiet-normal (QN), flare-normal (FN), and in the abnormal mode (AB), while in the abnormal mode, it has also been detected by other observers at other frequencies. The drift of subpulses is observed in the normal mode of emission only in the extreme components of the average profile. The normal mode is interrupted by nullings and transitions to the abnormal mode AB. In the AB mode, the structure of the activity zones at the edge of the outer cone is destroyed, the distance between the inner and outer cones increases almost twice, and the distance between the inner cone and the central region decreases. An analysis of our data has shown that the components of the outer and inner cones of the average profile are formed by the ordinary mode of radio emission (O-mode) and constitute a single cone emission of the pulsar. The central components of the average profile (wide and narrow) are formed by the extraordinary mode of emission (X-mode). Estimates of the height of the emission from the central region (X-mode) and the cone emission (O-mode) are obtained: 80 and 370 km, respectively. A microstructure with a submicrosecond time scale of <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11444_2025_1714_Article_IEq1.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="80" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\tau }_{\mu }} \leqslant 0.5 \mu s\)</EquationSource>  </InlineEquation> was discovered. Such a time scale corresponds well to the characteristic time of spark discharge development in the polar cap. For this value of <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11444_2025_1714_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\tau }_{\mu }}\)</EquationSource>  </InlineEquation>, the vacuum gap height must be <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11444_2025_1714_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="64" /> </InlineMediaObject> <EquationSource Format="TEX">\({{h}_{p}} \leqslant 750\)</EquationSource>  </InlineEquation> cm. Based on the steepness of the trailing edge of an individual pulse at the longitude of the first component, a limit on the value of the <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11444_2025_1714_Article_IEq4.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma \)</EquationSource>  </InlineEquation> factor of the relativistic secondary plasma was obtained: <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11444_2025_1714_Article_IEq5.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="59" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma \geqslant 260\)</EquationSource>  </InlineEquation>. The analysis showed that in 88% of cases, the normal mode (N) is realized, and in 81% of them—the QN mode and only in 19% the FN mode. The AB mode is only 12%. The dependence of the distance between the components of the outer and inner cones of radiation on the frequency is the same and corresponds to a power law with an index of –0.16.</p>

Pulsar B1237+25 at 111 MHz: Average Profile, Mode Switching, Nullings, and Microstructure

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发表日期：

2025年9月1日

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M. V. Popov,
T. V. Smirnova

摘要

Abstract

An analysis of observations of the pulsar B1237+25 at a frequency of 111 MHz has been presented. The observations have been carried out with the Large In-Phase Antenna (LPA) of the Pushchino Radio Astronomical Observatory, Lebedev Physical Institute. A new component in the average profile in the central region of the emission has been detected. This component with a half-width of 1.6 ms has been observed against the background of a more extended component with a half-width of 7 ms. This new component of the average profile at a frequency of 111 MHz manifests itself in all modes of the pulsar radio emission: quiet-normal (QN), flare-normal (FN), and in the abnormal mode (AB), while in the abnormal mode, it has also been detected by other observers at other frequencies. The drift of subpulses is observed in the normal mode of emission only in the extreme components of the average profile. The normal mode is interrupted by nullings and transitions to the abnormal mode AB. In the AB mode, the structure of the activity zones at the edge of the outer cone is destroyed, the distance between the inner and outer cones increases almost twice, and the distance between the inner cone and the central region decreases. An analysis of our data has shown that the components of the outer and inner cones of the average profile are formed by the ordinary mode of radio emission (O-mode) and constitute a single cone emission of the pulsar. The central components of the average profile (wide and narrow) are formed by the extraordinary mode of emission (X-mode). Estimates of the height of the emission from the central region (X-mode) and the cone emission (O-mode) are obtained: 80 and 370 km, respectively. A microstructure with a submicrosecond time scale of \({{\tau }_{\mu }} \leqslant 0.5 \mu s\) was discovered. Such a time scale corresponds well to the characteristic time of spark discharge development in the polar cap. For this value of \({{\tau }_{\mu }}\) , the vacuum gap height must be \({{h}_{p}} \leqslant 750\) cm. Based on the steepness of the trailing edge of an individual pulse at the longitude of the first component, a limit on the value of the \(\gamma \) factor of the relativistic secondary plasma was obtained: \(\gamma \geqslant 260\) . The analysis showed that in 88% of cases, the normal mode (N) is realized, and in 81% of them—the QN mode and only in 19% the FN mode. The AB mode is only 12%. The dependence of the distance between the components of the outer and inner cones of radiation on the frequency is the same and corresponds to a power law with an index of –0.16.