Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion Measures
Multiple studies have investigated potential frequency-dependent dispersion measures (DMs) in PSR B0329+54, with sensitivities at levels of 10 ^−3 pc cm ^−3 or higher, using frequencies below 1 GHz. Utilizing the extensive bandwidth of the upgraded Giant Metrewave Radio Telescope, we conducted simul...
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2025-01-01
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| author | Shyam S. Sharma Tetsuya Hashimoto Tomotsugu Goto Shotaro Yamasaki Simon C.-C. Ho |
| author_facet | Shyam S. Sharma Tetsuya Hashimoto Tomotsugu Goto Shotaro Yamasaki Simon C.-C. Ho |
| author_sort | Shyam S. Sharma |
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| description | Multiple studies have investigated potential frequency-dependent dispersion measures (DMs) in PSR B0329+54, with sensitivities at levels of 10 ^−3 pc cm ^−3 or higher, using frequencies below 1 GHz. Utilizing the extensive bandwidth of the upgraded Giant Metrewave Radio Telescope, we conducted simultaneous observations of this pulsar across a frequency range of 300–1460 MHz. Our observations reveal a distinct point in the pulse profile of PSR B0329+54 that appears to align remarkably well with the cold-plasma dispersion law, resulting in a unique measured DM across the entire frequency range. In contrast, using times of arrival from widely adopted pulsar timing techniques (e.g., FFTFIT) leads to frequency-dependent DMs. We investigated the potential causes of these frequency-dependent DMs in this pulsar and their relationship with the underlying magnetic field geometry corresponding to the radio emission. Our study reveals that all frequencies in the range 300–1460 MHz originate from a region no larger than 204 km, and the dipolar magnetic-field geometry model indicates that the emission region is centered at ~800 km from the star. This is the tightest constraint on the size of the emission region reported so far for PSR B0329+54 at the given frequencies, and it is at least 5 times more stringent than the existing emission height constraints based on the dipolar geometry model. |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-a8d1ff4ac9b64d4485c5779ed40049c72025-02-03T06:44:47ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198012610.3847/1538-4357/ada956Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion MeasuresShyam S. Sharma0Tetsuya Hashimoto1https://orcid.org/0000-0001-7228-1428Tomotsugu Goto2Shotaro Yamasaki3Simon C.-C. Ho4https://orcid.org/0000-0002-8560-3497Institute of Astronomy and Astrophysics , Academia Sinica, 11F of AS/NTU Astronomy-Mathematics Building, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan; Department of Physics, National Chung Hsing University , No. 145, Xingda Road, South District, Taichung 40227, TaiwanDepartment of Physics, National Chung Hsing University , No. 145, Xingda Road, South District, Taichung 40227, TaiwanInstitute of Astronomy, National Tsing Hua University , 101, Section 2, Kuang-Fu Road, Hsinchu 30013, TaiwanDepartment of Physics, National Chung Hsing University , No. 145, Xingda Road, South District, Taichung 40227, TaiwanResearch School of Astronomy and Astrophysics, The Australian National University , Canberra, ACT 2611, Australia; Centre for Astrophysics and Supercomputing, Swinburne University of Technology , Hawthorn, VIC 3122, Australia; OzGrav: The Australian Research Council Centre of Excellence for Gravitational Wave Discovery , Hawthorn, VIC 3122, Australia; ASTRO3D: The Australian Research Council Centre of Excellence for All-sky Astrophysics in 3D , ACT 2611, AustraliaMultiple studies have investigated potential frequency-dependent dispersion measures (DMs) in PSR B0329+54, with sensitivities at levels of 10 ^−3 pc cm ^−3 or higher, using frequencies below 1 GHz. Utilizing the extensive bandwidth of the upgraded Giant Metrewave Radio Telescope, we conducted simultaneous observations of this pulsar across a frequency range of 300–1460 MHz. Our observations reveal a distinct point in the pulse profile of PSR B0329+54 that appears to align remarkably well with the cold-plasma dispersion law, resulting in a unique measured DM across the entire frequency range. In contrast, using times of arrival from widely adopted pulsar timing techniques (e.g., FFTFIT) leads to frequency-dependent DMs. We investigated the potential causes of these frequency-dependent DMs in this pulsar and their relationship with the underlying magnetic field geometry corresponding to the radio emission. Our study reveals that all frequencies in the range 300–1460 MHz originate from a region no larger than 204 km, and the dipolar magnetic-field geometry model indicates that the emission region is centered at ~800 km from the star. This is the tightest constraint on the size of the emission region reported so far for PSR B0329+54 at the given frequencies, and it is at least 5 times more stringent than the existing emission height constraints based on the dipolar geometry model.https://doi.org/10.3847/1538-4357/ada956Interstellar mediumPulsarsPulsar timing methodNeutron stars |
| spellingShingle | Shyam S. Sharma Tetsuya Hashimoto Tomotsugu Goto Shotaro Yamasaki Simon C.-C. Ho Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion Measures The Astrophysical Journal Interstellar medium Pulsars Pulsar timing method Neutron stars |
| title | Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion Measures |
| title_full | Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion Measures |
| title_fullStr | Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion Measures |
| title_full_unstemmed | Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion Measures |
| title_short | Retracing the Cold Plasma Dispersion Law in Pulsar B0329+54: New Insights into Frequency-dependent Dispersion Measures |
| title_sort | retracing the cold plasma dispersion law in pulsar b0329 54 new insights into frequency dependent dispersion measures |
| topic | Interstellar medium Pulsars Pulsar timing method Neutron stars |
| url | https://doi.org/10.3847/1538-4357/ada956 |
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