Evidence of Orbital Evolution of Gigahertz-peaked Spectra in a Binary Millisecond Pulsar
- 1National Centre for Radio Astrophysics
Abstract
We present the first systematic investigation of the continuous orbital evolution of the gigahertz-peaked spectrum turnover frequency ( ν peak ) in the binary millisecond pulsar, PSR J2144−5237. Using approximately 50 hr of densely sampled observations spanning the ∼10 day orbit with the Parkes Ultra-Wideband Low-frequency receiver, we obtained continuous frequency coverage from 704 MHz to 4 GHz, enabling robust measurements of the spectral evolution throughout the binary orbit. We detect a clear and systematic modulation of the turnover frequency with orbital phase for both the first pulse and second pulse components, with both emission components exhibiting remarkably similar evolutionary trends despite originating from distinct emission regions within the pulsar magnetosphere. The correlated evolution of the two pulse components strongly suggests that the observed spectral variability is governed by propagation through the intrabinary environment. The large orbital modulation of turnover frequency can be explained by cyclotron resonance absorption in magnetized plasma associated with the companion, while alternative absorption mechanisms are unable to reproduce the observed behaviour. Modeling the orbital evolution of the turnover frequency within the cyclotron absorption framework can constrain the electron density distribution in the pulsar wind, estimate the magnetic field strength of the companion, and place limits on the geometry of the absorbing plasma and the binary system. This study establishes orbital evolution of the gigahertz-peaked spectrum as a powerful new diagnostic of the magnetized intrabinary medium and provides a hitherto unexplored probe of pulsar wind–companion interactions in eclipsing millisecond pulsar binaries.
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BibTeX
@article{sharan2026evidence,
title = {{Evidence of Orbital Evolution of Gigahertz-peaked Spectra in a Binary Millisecond Pulsar}},
author = {Rahul Sharan and Bhaswati Bhattacharyya},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea3fb},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea3fb},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Evidence of Orbital Evolution of Gigahertz-peaked Spectra in a Binary Millisecond Pulsar
AU - Rahul Sharan
AU - Bhaswati Bhattacharyya
PY - 2026
DA - 2026/10/09
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea3fb
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea3fb
AB - We present the first systematic investigation of the continuous orbital evolution of the gigahertz-peaked spectrum turnover frequency ( ν peak ) in the binary millisecond pulsar, PSR J2144−5237. Using approximately 50 hr of densely sampled observations spanning the ∼10 day orbit with the Parkes Ultra-Wideband Low-frequency receiver, we obtained continuous frequency coverage from 704 MHz to 4 GHz, enabling robust measurements of the spectral evolution throughout the binary orbit. We detect a clear and systematic modulation of the turnover frequency with orbital phase for both the first pulse and second pulse components, with both emission components exhibiting remarkably similar evolutionary trends despite originating from distinct emission regions within the pulsar magnetosphere. The correlated evolution of the two pulse components strongly suggests that the observed spectral variability is governed by propagation through the intrabinary environment. The large orbital modulation of turnover frequency can be explained by cyclotron resonance absorption in magnetized plasma associated with the companion, while alternative absorption mechanisms are unable to reproduce the observed behaviour. Modeling the orbital evolution of the turnover frequency within the cyclotron absorption framework can constrain the electron density distribution in the pulsar wind, estimate the magnetic field strength of the companion, and place limits on the geometry of the absorbing plasma and the binary system. This study establishes orbital evolution of the gigahertz-peaked spectrum as a powerful new diagnostic of the magnetized intrabinary medium and provides a hitherto unexplored probe of pulsar wind–companion interactions in eclipsing millisecond pulsar binaries.
SN - 0004-637X
SN - 1538-4357
ER -