The first JWST spectrum of a GRB afterglow: No bright supernova in observations of the brightest GRB of all time, GRB 221009A

Abstract

We present JWST and Hubble Space Telescope (HST) observations of the afterglow of GRB 221009A, the brightest gamma-ray burst (GRB) ever observed. This includes the first mid-IR spectra of any GRB, obtained with JWST/NIRSPEC (0.6-5.5 micron) and MIRI (5-12 micron), 12 days after the burst. Assuming that the intrinsic spectral slope is a single power-law, with $F_{\nu }\propto {\nu }^{-\beta }$, we obtain $\beta \approx 0.35$, modified by substantial dust extinction with $A_V=4.9$. This suggests extinction above the notional Galactic value, possibly due to patchy extinction within the Milky Way or dust in the GRB host galaxy. It further implies that the X-ray and optical/IR regimes are not on the same segment of the synchrotron spectrum of the afterglow. If the cooling break lies between the X-ray and optical/IR, then the temporal decay rates would only match a post jet-break model, with electron index $p<2$, and with the jet expanding into a uniform ISM medium. The shape of the JWST spectrum is near-identical in the optical/nIR to X-shooter spectroscopy obtained at 0.5 days and to later time observations with HST. The lack of spectral evolution suggests that any accompanying supernova (SN) is either substantially fainter or bluer than SN 1998bw, the proto-type GRB-SN. Our HST observations also reveal a disc-like host galaxy, viewed close to edge-on, that further complicates the isolation of any supernova component. The host galaxy appears rather typical amongst long-GRB hosts and suggests that the extreme properties of GRB 221009A are not directly tied to its galaxy-scale environment.

Accepted for publication to the Astrophysical Journal Letters for the GRB 221009A Special Issue. The results of this paper are under press embargo until March 28, 18 UT. 19 pages, 8 figures, 2 tables

References in corpus (25)

• Multi-messenger Observations of a Binary Neutron Star Merger
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• Long gamma-ray bursts and core-collapse supernovae have different environments
• The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope I. Overview of the instrument and its capabilities
• No supernovae associated with two long-duration gamma ray bursts
• An enigmatic long-lasting gamma-ray burst not accompanied by a bright supernova
• A Kilonova Following a Long-Duration Gamma-Ray Burst at 350 Mpc
• A nearby long gamma-ray burst from a merger of compact objects
• A long-duration gamma-ray burst with a peculiar origin
• The optically unbiased GRB host (TOUGH) survey. I. Survey design and catalogs
• Short GRB Host Galaxies I: Photometric and Spectroscopic Catalogs, Host Associations, and Galactocentric Offsets
• The case for a minute-long merger-driven gamma-ray burst from fast-cooling synchrotron emission
• Gamma-ray burst progenitors
• The peculiar short-duration GRB 200826A and its supernova
• Short GRB Host Galaxies. II. A Legacy Sample of Redshifts, Stellar Population Properties, and Implications for their Neutron Star Merger Origins
• Diversity of GRB energetics vs. SN homogeneity: supernova 2013cq associated with the gamma-ray burst 130427A
• GeV emission from a compact binary merger
• How common are long Gamma-Ray Bursts in the Local Universe?
• Probing Kilonova Ejecta Properties Using a Catalog of Short Gamma-Ray Burst Observations
• GRB jet structure and the jet break
• Signatures of R-process Enrichment in Supernovae from Collapsars
• Tungsten vs Selenium as a potential source of kilonova nebular emission observed by Spitzer
• Are the host galaxies of Long Gamma-Ray Bursts more compact than star-forming galaxies of the field?
• Detailed multi-wavelength modelling of the dark GRB 140713A and its host galaxy

Cited by in corpus (22)

• JWST detection of heavy neutron capture elements in a compact object merger
• Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow
• Observability of the very-high-energy emission from GRB 221009A
• Observation of spectral lines in the exceptional GRB 221009A
• The Possibility of Modeling the Very High Energy Afterglow of GRB 221009A in a Wind Environment
• A Sensitive Search for Supernova Emission Associated with the Extremely Energetic and Nearby GRB 221009A
• GRB 221009A: An ordinary nearby GRB with extraordinary observational properties
• A Narrow Uniform Core with a Wide Structured Wing: Modeling the TeV and Multi-wavelength Afterglows of GRB 221009A
• Constraints on Axion-like Particles from the Observation of GRB 221009A by LHAASO
• Towards a model of photon-axion conversion in the host galaxy of GRB 221009A
• A short survey of matter-antimatter evolution in the primordial universe
• Carpet-3 detection of a photon-like air shower with estimated primary energy above 100 TeV in a spatial and temporal coincidence with GRB 221009A
• The brightest GRB ever detected: GRB 221009A as a highly luminous event at z = 0.151
• Swift/UVOT: 18 Years of Long GRB Discoveries and Advances
• GRB 221009A: Spectral signatures based on ALPs candidates
• The expansion of the GRB 221009A afterglow
• Axion-like Particle Effects on Photon Polarization in High-Energy Astrophysics
• GRB 180728A and SN 2018fip: the nearest high-energy cosmological gamma-ray burst with an associated supernova
• The possibility of multi-TeV secondary gamma rays from GRB221009A
• The metallicity dependence of long-duration gamma-ray bursts
• A photohadronic interpretation of the H.E.S.S. afterglow observations from GRB 221009A
• Constraining dark photon parameters based on the very high energy observations of blazars