GCN Circular 45597
Subject
GRB 260909A: NOEMA detection
Event
Date
2026-09-16T18:28:12Z (2 days ago)
From
Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo@gmail.com>
Via
email
A. de Ugarte Postigo (LAM), M. Bremer (IRAM), C. C. Thoene (AbAO), S. Basa (LAM), S. Geier (GTC), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), M. Michalowski (AOI-AMU), D. A. Perley (LJMU), D. B. Malesani (DAWN/NBI and Radboud), B. Schneider (LAM), N.R. Tanvir (U. Leicester), L. Resmi (IIST), K. Misra (ARIES) report:
We observed the field of GRB 260909A (Saccardi et al. GCN 45534, Wang et al. GCN 45538, Brunet et al. GCN 45553) with the NOEMA interferometer, located at Plateau de Bure (France). Observations started on the 14th September 2026 at 22:55 UT (5.48 days after the GRB) at 81 and 96 GHz simultaneously. An object is clearly detected consistent with the position of the X-ray afterglow (Mao et al., GCN 45543), at a combined flux density of ~0.4 mJy. . The spectral slope between our two observing bands is beta ~ -1.3 +/- 0.6 (where F_nu is proportional to nu^beta). Although this is a rather steep value for this observing time, the large uncertainties make it compatible with a normal spectral slope of a GRB afterglow, where the peak frequency falls at lower frequencies.
The best coordinates of the source are (J2000):
R.A. = 00:52:08.462
Dec. = +24:11:47.12
With an uncertainty of ~ 0.2 "
We acknowledge excellent support from the IRAM staff. Based on observations carried out under project number S26DT with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).