GCN Circular 40036
Subject
GRB 250322A: 10 GHz VLA radio upper limits
Event
Date
2025-04-04T01:52:21Z (6 months ago)
From
Genevieve Schroeder at Cornell University <genevieveschroeder@u.northwestern.edu>
Via
Web form
G. Schroeder (Cornell), T. Laskar (Utah), W. Fong, J. Rastinejad (Northwestern) report:
We observed the position of the short GRB 250322A (Gupta et al., GCN 39835;
Tembhurnikar et al., GCN 39849; Ridnaia et al., GCN 39873) with the Karl G. Jansky Very Large Array (VLA) under program 25A-063 (PI Schroeder) beginning on 2025 March 25 at 22:07 UT (3.25 days post-burst) for 1 hour at a mean frequency of 10 GHz.
Based on preliminary analysis, we do not detect any radio emission at or near the position of the XRT afterglow (Perri et al., GCN 39855), to a 3 sigma limit of 20 microJy. We additionally do not detect the putative host galaxy in our image (Martin-Carrillo et al., GCN 39842; Becerra et al., GCN 39844; 39845l; Kilpatrick & Fong, GCN 39846; Fong et al., GCN 39852, Schneider et al., GCN 39863). Assuming a redshift of z = 0.42 (Fong et al., GCN 39852; Yang et al. GCN 39859), these observations imply a limit on the radio-inferred star formation rate of < 18 M_sol/year (following the formalism of Greiner et al. 2016). Using the putative host redshift, the lack of radio afterglow detection implies a radio luminosity of < 1.3e29 erg/Hz/s, which is a factor of >~4 lower than the median radio luminosity of radio-detected short GRBs at a similar epoch and rest frame time (Laskar et. al. 2022). Overall, this limit places GRB 250322A in the bottom 25% of radio-observed short GRBs with redshift determinations, in terms of radio luminosity.
We thank the VLA staff for quickly approving and executing these observations.