FRB 20250316A is likely associated with NGC 4141, but is not spatially coincident with either SN 2008X or SN 2009E

ATel #17086; Calvin Leung (UC Berkeley) on behalf of the CHIME/FRB Collaboration
on 19 Mar 2025; 04:05 UT
Credential Certification: Kaitlyn Shin (kshin@mit.edu)

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We have successfully used early commissioning data from the full CHIME/FRB Outriggers array to obtain a sub-arcsecond VLBI position for fast radio burst (FRB) 20250316A (ATel #17081). Early tests reveal that the astrometric accuracy of the Outriggers array is on the order of 0.05'' x 0.1'', but uncertainty quantification is not yet available for the Green Bank and Hat Creek Outrigger stations.

We report below a refined localization relative to ATel #17081: we have re-run the baseband localization with temperature corrections, and inflated the resulting uncertainties to 80'' in each dimension. Using the baseband localization as a prior, we have refined the position using the 66-km baseline between CHIME and the KKO station, which constrains the position more precisely along one axis using a previously-validated localization procedure (Lanman et al. (2025), CHIME/FRB Collaboration et al. (2025)). The below CHIME-KKO position is insensitive to the systematic errors present in the baseband pipeline; it lies within 2 sigmas of the temperature-corrected baseband position (2' offset in EW) and places the FRB in the western half of NGC 4141. In agreement with ATel #17081, the FRB remains robustly associated with NGC 4141. However, both SN 2008X (Boles 2008; Madison et al. 2008) and SN 2009E (Boles 2009; Pastorello et al. 2011) fall well outside of the CHIME-KKO localization contour, ruling out a direct association between FRB 20250316A and either SN. The ellipse coordinates are as follows:

ra: 182.4365 degrees

dec: +58.8552 degrees

a_error (semi-major axis): 80''

b_error (semi-minor axis): 1.8''

theta: 9.48 degrees east of North

kko localization ellipse