DOI

https://doi.org/10.48717/e6je-nt79

Project

RG013

Title

RG013A

Abstract

GRB 221009A is an incredibly bright, closeby (z = 0.151), very high-energy GRB. Thanks to its vicinity and brightness, GRB 221009A represents an excellent target not only for flux density monitoring to study the emission mechanism of very-high energy photons (>100 GeV), but also to directly resolve the expanding ejecta launched during the stellar death, to constrain the proper motion of the jet centroid and to study the structure of the jet, which can be done only with high angular resolution observations. Thus, we propose to perform an EVN + KVN follow-up of GRB 221009A at 6 (C-band) and 1.3 cm (K-band) over six epochs, for a total of 24 hours. The observation will be performed with the following cadence: regarding the K-band, a first 4-hour-long observation should be carried within 10 days post-burst, followed by two other 4-hour-long observations 30 and 100 days after the first one; concerning the C-band, we request two 4-hour-long observations around 30 and 100 days after the first K-band observation (in order to get two almost simultaneous K- and C-band observations), followed by a last 4-hour-long observation to be performed within a year post-burst. With the proposed follow-up campaign we want to (i) characterise the dynamics of the ejecta through the expansion (on-axis GRB) or the proper motion (off-axis GRB) of the jet, (ii) constrain the geometry of the outflow and (iii) derive the microphysical parameters governing the dynamics and the surrounding environment of the GRB afterglow through the modelling of the synchrotron spectrum.