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arXiv · 2308.06813

Deep Synoptic Array Science: Polarimetry of 25 New Fast Radio Bursts Provides Insights into their Origins

Myles B. Sherman·Liam Connor·Vikram Ravi·Casey Law·Ge Chen·Morgan Catha·Jakob T. Faber·Gregg Hallinan·Charlie Harnach·Greg Hellbourg·Rick Hobbs·David Hodge·Mark Hodges·James W. Lamb·Paul Rasmussen·Kritti Sharma·Jun Shi·Dana Simard·Jean Somalwar·Reynier Squillace·Sander Weinreb·David P. Woody·Nitika Yadlapalli
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Abstract

We report on a full-polarization analysis of the first 25 as yet non-repeating FRBs detected at 1.4 GHz by the 110-antenna Deep Synoptic Array (DSA-110) during commissioning observations. We present details of the data-reduction, calibration, and analysis procedures developed for this novel instrument. Faraday rotation measures (RMs) are searched between $\pm10^6$ rad m$^{-2}$ and detected for 20 FRBs with magnitudes ranging from $4-4670$ rad m$^{-2}$. $15/25$ FRBs are consistent with 100% polarization, 10 of which have high ($\ge70\%$) linear-polarization fractions and 2 of which have high ($\ge30\%$) circular-polarization fractions. Our results disfavor multipath RM scattering as a dominant depolarization mechanism. Polarization-state and possible RM variations are observed in the four FRBs with multiple sub-components. We combine the DSA-110 sample with polarimetry of previously published FRBs, and compare the polarization properties of FRB sub-populations and FRBs with Galactic pulsars. Although FRB polarization fractions are typically higher than those of Galactic pulsars, and cover a wider range than those of pulsar single pulses, they resemble those of the youngest (characteristic ages $<10^{5}$ yr) pulsars. Our results support a scenario wherein FRB emission is intrinsically highly linearly polarized, and propagation effects can result in conversion to circular polarization and depolarization. Young pulsar emission and magnetospheric-propagation geometries may form a useful analogy for the origin of FRB polarization.

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Myles B. Sherman, Liam Connor, Vikram Ravi, Casey Law, Ge Chen, Morgan Catha, Jakob T. Faber, Gregg Hallinan, Charlie Harnach, Greg Hellbourg, Rick Hobbs, David Hodge, Mark Hodges, James W. Lamb, Paul Rasmussen, Kritti Sharma, Jun Shi, Dana Simard, Jean Somalwar, Reynier Squillace, Sander Weinreb, David P. Woody, Nitika Yadlapalli. 2023-08-13. Deep Synoptic Array Science: Polarimetry of 25 New Fast Radio Bursts Provides Insights into their Origins. https://doi.org/10.3847/1538-4357%2Fad275e

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