FRBs Lensed by Point Masses I. Lens Mass Estimation for Doubly Imaged FRBs

Abstract

Fast radio bursts (FRBs) are bright radio transient events with durations on the order of milliseconds. The majority of FRB sources discovered so far have a single peak, with the exception of a few showing multiple-peaked profiles, the origin of which is unknown. In this work, we show that the strong lensing effect of a point mass or a point mass $+$ external shear on a single-peak FRB can produce double peaks (i.e. lensed images). In particular, the leading peak will always be more magnified and hence brighter than the trailing peak for a point-mass lens model, while the point-mass $+$ external shear lens model can produce a less magnified leading peak. We find that, for a point-mass lens model, the combination of lens mass $M$ and redshift $z_l$ in the form of $M(1+z_l)$ can be directly computed from two observables -- the delayed time $\Delta t$ and the flux ratio of the leading peak to the trailing peak $R$. For a point-mass $+$ external shear lens model, upper and lower limits in $M(1+z_l)$ can also be obtained from $\Delta t$ and $R$ for a given external shear strength. In particular, tighter lens mass constraints can be achieved when the observed $R$ is larger. Lastly, we show the process of constraining lens mass using the observed values of $\Delta t$ and $R$ of two double-peaked FRB sources, i.e. FRB 121002 and FRB 130729, as references, although the double-peaked profiles are not necessarily caused by strong lensing.

11 pages, 5 figures, ApJ in press

References in corpus (16)

• A bright millisecond radio burst of extragalactic origin
• The direct localization of a fast radio burst and its host
• The Host Galaxy and Redshift of the Repeating Fast Radio Burst FRB 121102
• Fast Radio Bursts
• H0LiCOW V. New COSMOGRAIL time delays of HE0435-1223: $H_0$ to 3.8% precision from strong lensing in a flat $\Lambda$CDM model
• The Repeating Fast Radio Burst FRB 121102 as Seen on Milliarcsecond Angular Scales
• A Second Source of Repeating Fast Radio Bursts
• Nine New Repeating Fast Radio Burst Sources from CHIME/FRB
• FRB 121102 is coincident with a star forming region in its host galaxy
• The Physics of Fast Radio Bursts
• An absence of fast radio bursts at intermediate galactic latitudes
• A Fast Radio Burst discovered in FAST drift scan survey
• Luminosity-duration relations and luminosity functions of repeating and non-repeating fast radio bursts
• Nanolensed fast Radio Bursts
• The effects of plasma lensing on the inferred dispersion measures of Fast Radio Bursts
• Parkes transient events: I. Database of single pulses, initial results and missing FRBs

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• FRBs Lensed by Point Masses II. The multi-peaked FRBs from the point view of microlensing
• Fast radio bursts at the dawn of the 2020s
• Light curves and polarizations of gravitationally lensed kilonovae