TITLE:   GCN CIRCULAR
NUMBER:  39933
SUBJECT: GRB 250327B: ALMA detection
DATE:    25/03/29 21:34:47 GMT
FROM:    Tanmoy Laskar at U of Utah <tanmoylaskar@gmail.com>

T. Laskar (University of Utah), N. Franz, C. Christy, K. D. Alexander (University of Arizona), E. Berger (Harvard University), R. Chornock (UC Berkeley), W. Fong (Northwestern University), R. Margutti (UC Berkeley), P. Schady (University of Bath), and G. Schroeder (Cornell University), report on behalf of a larger collaboration:

“We observed GRB 250327B (Bouchet et al., GCN 39888) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 97.5 GHz beginning on 2025 March 29 at 01:45 UT (28.5 hours after the burst). 

Preliminary analysis reveals a mm source with flux density of ~ 0.5 mJy at position:

RA (J2000) = 11:47:06.72
Dec (J2000) = +29:50:24.71

with an uncertainty of 0.05" in each coordinate. This is consistent with the X-ray position (Bouchet et al., GCN 39888; Page et al. GCN 39895), optical position (Moskvitin et al., GCN 39889; Xin et al., GCN 39890), and radio position (Christy et al., GCN 39932). 

We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations."