Constraining small scale magnetic fields through plasma lensing: Application to the Black widow eclipsing pulsar binary

Abstract

In regions with strongly varying electron density, radio emission can be magnified significantly by plasma lensing. In the presence of magnetic fields, magnification in time and frequency will be different for two circular polarizations. We show how these effects can be used to measure or constrain the magnetic field parallel to the line of sight, $B_{\parallel }$, as well as its spatial structure, ${\sigma }_{B_{\parallel }}$, in the lensing region. In addition, we discuss how generalized Faraday rotation can constrain the strength of the perpendicular field, $B_{\perp }$. We attempt to make such measurements for the Black Widow pulsar, PSR~B1957+20, in which plasma lensing was recently discovered. For this system, pressure equilibrium suggests $B\gtrsim 20$G at the interface between the pulsar and companion winds, where the radio eclipse starts and ends, and where most lensing occurs. We find no evidence for large-scale magnetic fields, with, on average, $B_{\parallel }=0.02\pm 0.09$G over the egress lensing region. From individual lensing events, we strongly constrain small scale magnetic structure to ${\sigma }_B<10$mG, thus excluding scenarios with a strong but rapidly varying field. Finally, from the lack of reduction of average circular polarization in the same region, we rule out a strong, quasi-transverse field. We cannot identify any plausible scenario in which a large magnetic field in this system is concealed, leaving the nature of the interface between the pulsar and companion winds an enigma. Our method can be applied to other sources showing plasma lensing, including other eclipsing pulsars and fast radio bursts, to study the local properties of the magnetic field.

arXiv comment11 pages, 8 figures. submitted to MNRAS

References in corpus (18)

• Astropy: A Community Python Package for Astronomy
• A Repeating Fast Radio Burst
• An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102
• Dense magnetized plasma associated with a fast radio burst
• Evidence for a Massive Neutron Star from a Radial-Velocity Study of the Companion to the Black Widow Pulsar PSR B1957+20
• The Green Bank Northern Celestial Cap Pulsar Survey - I: Survey Description, Data Analysis, and Initial Results
• Lensing of Fast Radio Bursts by Plasma Structures in Host Galaxies
• Using Neutron Star Observations to Determine Crust Thicknesses, Moments of Inertia, and Tidal Deformabilities
• FRB microstructure revealed by the real-time detection of FRB170827
• Orbital Variability in the Eclipsing Pulsar Binary PSR B1957+20
• Pulsar emission amplified and resolved by plasma lensing in an eclipsing binary
• A Metal-Rich Low-Gravity Companion to a Massive Millisecond Pulsar
• Green Bank Telescope Studies of Giant Pulses from Millisecond Pulsars
• Mode changing and giant pulses in the millisecond pulsar PSR B1957+20
• First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved
• Dynamic spectral mapping of interstellar plasma lenses
• Descattering of Giant Pulses in PSR B1957+20
• Polarimetry of the eclipsing pulsar PSR J1748$-$2446A

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• A Highly Variable Magnetized Environment in a Pulsar Binary resembling Fast Radio Bursts
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• The effects of plasma lensing on the inferred dispersion measures of Fast Radio Bursts
• The FAST Galactic Plane Pulsar Snapshot survey: VIII. 116 binary pulsars
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• Unraveling the Eclipse Mechanism of a Binary Millisecond Pulsar Using Broadband Radio Spectra
• Timing of PSR J2055+3829, an eclipsing black widow pulsar discovered with the Nançay Radio Telescope
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