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The Optical Light Curve of GRB 221009A: The Afterglow and the Emerging Supernova

Abstract:
Abstract We present extensive optical photometry of the afterglow of GRB 221009A. Our data cover 0.9–59.9 days from the time of Swift and Fermi gamma-ray burst (GRB) detections. Photometry in rizy -band filters was collected primarily with Pan-STARRS and supplemented by multiple 1–4 m imaging facilities. We analyzed the Swift X-ray data of the afterglow and found a single decline rate power law f ( t ) ∝ t −1.556±0.002 best describes the light curve. In addition to the high foreground Milky Way dust extinction along this line of sight, the data favor additional extinction to consistently model the optical to X-ray flux with optically thin synchrotron emission. We fit the X-ray-derived power law to the optical light curve and find good agreement with the measured data up to 5−6 days. Thereafter we find a flux excess in the riy bands that peaks in the observer frame at ∼20 days. This excess shares similar light-curve profiles to the Type Ic broad-lined supernovae SN 2016jca and SN 2017iuk once corrected for the GRB redshift of z = 0.151 and arbitrarily scaled. This may be representative of an SN emerging from the declining afterglow. We measure rest-frame absolute peak AB magnitudes of M g = −19.8 ± 0.6 and M r = − 19.4 ± 0.3 and M z = −20.1 ± 0.3. If this is an SN component, then Bayesian modeling of the excess flux would imply explosion parameters of M ej = 7.1 − 1.7 + 2.4 M ⊙ , M Ni = 1.0 − 0.4 + 0.6 M ⊙ , and v ej = 33,900 − 5700 + 5900 km s −1 , for the ejecta mass, nickel mass, and ejecta velocity respectively, inferring an explosion energy of E kin ≃ 2.6–9.0 × 10 52 erg.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.3847/2041-8213/acc101

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Role:
Author
ORCID:
0000-0003-1916-0664
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Institution:
University of Oxford
Role:
Author
ORCID:
0000-0002-8229-1731
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Institution:
University of Oxford
Role:
Author
ORCID:
0000-0003-2705-4941
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Role:
Author
ORCID:
0000-0003-1059-9603
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Role:
Author
ORCID:
0000-0002-5814-4061


Publisher:
American Astronomical Society
Journal:
The Astrophysical Journal Letters More from this journal
Volume:
946
Issue:
1
Pages:
L22-L22
Publication date:
2023-03-28
DOI:
EISSN:
2041-8213
ISSN:
2041-8205


Language:
English
Keywords:
Pubs id:
1336882
Local pid:
pubs:1336882
Source identifiers:
W4361216445
Deposit date:
2026-01-14
ARK identifier:
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