The expansion of the GRB 221009A afterglow
Artikel i vetenskaplig tidskrift, 2024

We observed γ-ray burst (GRB) 221009A using very long baseline interferomety (VLBI) with the European VLBI Network (EVN) and the Very Long Baseline Array (VLBA), over a period spanning from 40 to 262 days after the initial GRB. The high angular resolution (mas) of our observations allowed us, for the second time ever, after GRB 030329, to measure the projected size, s, of the relativistic shock caused by the expansion of the GRB ejecta into the surrounding medium. Our observations support the expansion of the shock with a > 4σ-equivalent significance, and confirm its relativistic nature by revealing an apparently superluminal expansion rate. Fitting a power law expansion model, s α ta, to the observed size evolution, we find a slope a = 0.69α' 0.14+0.13. Fitting the data at each frequency separately, we find different expansion rates, pointing to a frequency-dependent behaviour. We show that the observed size evolution can be reconciled with a reverse shock plus forward shock, provided that the two shocks dominate the emission at different frequencies and, possibly, at different times.

Techniques: interferometric

Techniques: high angular resolution

Radio continuum: general

Gamma-ray burst: general

Gamma-ray burst: individual: GRB 221009A

Författare

S. Giarratana

Istituto di Radioastronomia

Universita di Bologna

O. S. Salafia

Istituto nazionale di astrofisica (INAF)

Istituto Nazionale di Fisica Nucleare

M. Giroletti

Istituto di Radioastronomia

G. Ghirlanda

Istituto nazionale di astrofisica (INAF)

Istituto Nazionale di Fisica Nucleare

L. Rhodes

University of Oxford

P. Atri

Netherlands Institute for Radio Astronomy (ASTRON)

B. Marcote

JOINT INSTITUTE FOR V.L.B.I. IN EUROPE (J.I.V.E.)

Jun Yang

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

T. An

Shanghai Astronomical Observatory

Chinese Academy of Sciences

G. A. Anderson

International Centre for Radio Astronomy Research

J. S. Bright

University of Oxford

W. Farah

SETI Institute

University of California

R. P. Fender

University of Cape Town

University of Oxford

J. K. Leung

University of Toronto

The Hebrew University Of Jerusalem

S. E. Motta

Istituto nazionale di astrofisica (INAF)

University of Oxford

M.A. Pérez-Torres

Universidad de Zaragoza

Instituto de Astrofisica de Andalucía (IAA)

European University Cyprus

A. J. van der Horst

George Washington University

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 690 A74

Opticon RadioNet Pilot

Europeiska kommissionen (EU) (EC/H2020/101004719), 2021-03-01 -- 2025-02-28.

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/202348524

Relaterade dataset

URI: https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ A+A/690/A74

Mer information

Senast uppdaterat

2024-11-05