TITLE:   GCN CIRCULAR
NUMBER:  44235
SUBJECT: GRB 260310A: Continued VLA Multi-frequency Radio Observations
DATE:    26/04/08 02:27:55 GMT
FROM:    Genevieve Schroeder at Cornell University <genevieveschroeder@u.northwestern.edu>

G. Schroeder (Cornell), D. A. Perley (LJMU), and T. Laskar (Utah) report on behalf of a larger collaboration:

The Karl G. Jansky Very Large Array observed the location of the afterglow (Hinds et al., TNS AstroNote 2026-65; Konno et al., GCN 43974) associated with GRB 260310A (Fermi GBM Team, GCN 43951; Hamburg & Meegan, GCN 43975) using all available receivers from L-band to Q-band, providing nearly continuous spectral coverage from 1 to 50 GHz, as a part of our multi-frequency public campaign (Perley et al., GCN 44160). Observations were carried out on UT 2026-04-04 between 08:42 and 12:19 UT, approximately 25.2 days after the GRB.

Preliminary flux densities are:

| freq(GHz) |  flux(mJy) 	|
|-----------|----------------|
| 1.5     | 1.74 +/- 0.06 |
| 3     	| 5.00 +/- 0.04 |
| 6     	| 8.39 +/- 0.05 |
| 10    	| 8.93 +/- 0.12 |
| 15    	| 8.16 +/- 0.22 |
| 22   	| 7.34 +/- 0.23 |
| 33    	| 6.14 +/- 0.19 |
| 45    	| 5.25 +/- 0.19 |

Compared to previous radio observations (Rhodes et al., GCN 44005; Giarratana et al., GCN 44045; Ho et al., GCN 44057; Ho et al., GCN 44134, Perley et al., GCN 44160), the afterglow is brightening at lower frequencies (< 10 GHz) and fading at higher frequencies (> 10 GHz).

We thank the NRAO staff for scheduling and executing these observations. 

Further observations are planned.