James Webb Space Telescope Feed Post

JWST detection of heavy neutron capture elements in a compact object merger

Ground based optical and IR imaging of the afterglow of GRB 230307A. Panel (a) shows a legacy survey image of the field, the green trapezoid shows the IPN error box at the time of afterlgow discovery, with the blue dotted lines showing its ultimate refinement. The shaded regions represent observations taken with ULTRACAM 1.4 days post burst. Panel (b) shows the same image, zoomed in to a region around the afterglow. The red source in the centre is an unrelated foreground star (confirmed both by its measured proper motion and spectrum), and several other galaxies can also be seen. Panel (c) shows an ULTRACAM image, where the afterglow can be seen to the north-east of the star. The remaining panels (d,e,f) show the afterglow imaged on ~ 10 - 20 day timescales. At 10 days the source is undetected in deep FORS2 i-band imaging, but well detected in the K-band with Gemini-South. This very red colour was suggestive of an additional component over and above any afterglow, and motivated further follow-up