TITLE:   GCN CIRCULAR
NUMBER:  34468
SUBJECT: GRB 230812B: NOEMA detection
DATE:    23/08/17 18:26:36 GMT
FROM:    Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>

A. de Ugarte Postigo, (OCA-CNRS), J. M. Winters (IRAM), C. C. Thoene (ASU-CAS), S. Antier (OCA), J. F. Agui-Fernandez (IAA-CSIC), M. Bremer (IRAM), D. A. Perley (LJMU), S. Martin (ESO, ALMA) report,

We observed the afterglow of GRB 230812B (Roberts et al. GCN34391, Scotton et al. GCN 34392, Zheng & Filippenko GCN 34395, Beardmore et al. GCN 34400) with NOEMA in the 3mm band. The observation started on August 16 at 13:49 UT (3.79 days after the burst) and included observations at 75 and 89.5 GHz side bands.

The afterglow, previously detected in radio by AMI-LA (Rhodes et al. GCN34433) is weakly detected at 75 GHz with a flux density of 0.14 mJy. At a redshift of z = 0.36 (de Ugarte Postigo et al. GCN 34409) the afterglow currently has a luminosity of <10^30 erg/s/Hz which is amongst the least luminous afterglows detected at these frequencies.