http://arxiv.org/abs/2305.11477
Temporal broadening is a commonly observed property of fast radio bursts (FRBs), associated with turbulent media which cause radiowave scattering. Similarly to dispersion, scattering is an important probe of the media along the line of sight to an FRB source, such as the circum-burst or circum-galactic mediums (CGM). Measurements of characteristic scattering times alone are insufficient to constrain the position of the dominant scattering media along the line of sight. However, where more than one scattering screen exists, Galactic scintillation can be leveraged to form strong constraints. We quantify the scattering and scintillation in 10 FRBs with 1) known host galaxies and redshifts and 2) captured voltage data enabling high time resolution analysis, obtained from the Commensal Real-time ASKAP (Australian Square Kilometre Array Pathfinder) Fast Transient survey science project (CRAFT). We find strong evidence for two screens in three cases. For FRBs 20190608B and 20210320C, we find evidence for scattering screens less than approximately 16.7 and 3000 kpc respectively, from their sources. For FRB 20201124A we find evidence for a scattering screen at $\approx$26 kpc. Each of these measures is consistent with the scattering occurring in the host ISM (inter-stellar medium) or CGM. If pulse broadening is assumed to be contributed by the host galaxy ISM or circum-burst environment, the definitive lack of observed scintillation in four FRBs in our sample suggests that existing models may be over-estimating scattering times associated with the Milky Way’s ISM, similar to the anomalously low scattering observed for FRB 20201124A.
M. Sammons, A. Deller, M. Glowacki, et. al.
Mon, 22 May 23
53/60
Comments: 13 pages, 9 figures, 1 table. Submitted to MNRAS