TITLE:   GCN CIRCULAR
NUMBER:  40212
SUBJECT: GRB250419A: VLA radio detection
DATE:    25/04/22 21:29:01 GMT
FROM:    Genevieve Schroeder at Cornell University <genevieveschroeder@u.northwestern.edu>

Genevieve Schroeder (Cornell), Anna Ho (Cornell), Daniel Perley (LJMU) report:

We observed the position of the SVOM/ECLAIRs GRB 250419A (Wang et al. GCN 40168), with the NSF’s Karl G. Jansky Very Large Array (VLA) under program 25A-374 (PI Perley) beginning on 2025 April 22 at 06:37 UT (3.2 days post discovery) at a mean frequency of 10 GHz (4 GHz bandwidth). Based on preliminary analysis, we clearly detect a radio source with a 10 GHz flux density of ~320 uJy and a position of:

RA(J2000) = 13:29:37.275
Dec(J2000) = +07:02:27.63

with an uncertainty of ~0.2" in each coordinate. This is consistent with the location of the optical counterpart of GRB 250419A (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon et al., GCN 40183; Kuin, GCN 40185; Wu et al., GCN 40186; Xie et al., GCN 40187; Jiang et al., GCN 40188; Ghosh et al., GCN 40189; Bochenek & Perley, GCN 40190; Pankov et al., GCN 40202; Gianluca Masi, GCN 40206; Giovanni Calapai & Massa S. Giorgio, GCN 40209; Lagioia et al., GCN 40210).

At the redshift of GRB 250419A (Thakur et al., GCN 40174), the VLA observation corresponds to a 18.5 GHz (rest-frame) luminosity of ~1e31 erg/s/Hz. This luminosity is similar to a typical long GRB radio afterglow at a similar epoch (e.g., Chandra & Frail 2012, ApJ 746, 156, Laskar et al. 2023, ApJ, 946, 23).

Additional followup is planned.

We thank the VLA staff for quickly approving and executing these observations.