Abstract
GRB 221009A (z = 0.151) is one of the closest known long γ-ray bursts (GRBs). Its extreme brightness across all electromagnetic wavelengths provides an unprecedented opportunity to study a member of this still-mysterious class of transients in exquisite detail. We present multiwavelength observations of this extraordinary event, spanning 15 orders of magnitude in photon energy from radio to γ-rays. We find that the data can be partially explained by a forward shock (FS) from a highly collimated relativistic jet interacting with a low-density, wind-like medium. Under this model, the jet’s beaming-corrected kinetic energy (E K ∼ 4 × 1050 erg) is typical for the GRB population. The radio and millimeter data provide strong limiting constraints on the FS model, but require the presence of an additional emission component. From equipartition arguments, we find that the radio emission is likely produced by a small amount of mass (≲6 × 10−7 M ⊙) moving relativistically (Γ ≳ 9) with a large kinetic energy (≳1049 erg). However, the temporal evolution of this component does not follow prescriptions for synchrotron radiation from a single power-law distribution of electrons (e.g., in a reverse shock or two-component jet), or a thermal-electron population, perhaps suggesting that one of the standard assumptions of afterglow theory is violated. GRB 221009A will likely remain detectable with radio telescopes for years to come, providing a valuable opportunity to track the full lifecycle of a powerful relativistic jet.
| Original language | English (US) |
|---|---|
| Article number | L23 |
| Journal | Astrophysical Journal Letters |
| Volume | 946 |
| Issue number | 1 |
| DOIs | |
| State | Published - Mar 1 2023 |
Funding
GMRT observations for this study were obtained via project 43_039 (PI: Laskar). We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. VLA and VLBA observations for this study were obtained via projects VLA/22B-062 and VLBA/22B-305, respectively (PI: Laskar). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The Australia Telescope Compact Array is part of the Australia Telescope National Facility ( https://ror.org/05qajvd42 ), which is funded by the Australian Government for operation as a National Facility managed by CSIRO. We acknowledge the Gomeroi people as the Traditional Owners of the Observatory site. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. This work makes use of data supplied by the UK Swift Science Data Centre at the University of Leicester and of data obtained through the High Energy Astrophysics Science Archive Research Center On-line Service, provided by the NASA/Goddard Space Flight Center. This work was supported under NASA contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2022.1.01433.T. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. This work is based on observations carried out under project number S22BE with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). We thank Melanie Krips and the NOEMA staff for executing our observations, undertaking the reduction, and providing us with reduced data products. We thank the SMA staff for rapidly approving our ToO request and Mark Gurwell for reducing the data and providing us with the flux-density measurements. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. We recognize that Maunakea is a culturally important site for the indigenous Hawaiian people; we are privileged to study the cosmos from its summit. We thank J. Racusin and E. Burns for contribution to the NuSTAR observations and for helpful comments. We thank the anonymous referee for their rapid and constructive review of this work. T.E. is supported by NASA through the NASA Hubble Fellowship grant No. HST-HF2-51504.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. S.B. is supported by a Dutch Research Council (NWO) Veni Fellowship (VI.Veni.212.058). The work of R.Y. is partially supported by JSPS KAKENHI (grant No. JP22H01251). R.B.D. acknowledges support from the National Science Foundation under grant No. 2107932. A.G. acknowledges the financial support from the Slovenian Research Agency (research core funding No. P1-0031, infrastructure program I0-0033, and project grant No. J1-8136, J1-2460). The TReX group at Berkeley is partially supported by NSF grant Nos. AST-2221789 and AST-2224255.
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science