Earliest simultaneous multi-color optical observations of GRB 230328B: from 41 seconds to the host-galaxy identification
Abstract
We present a multiwavelength study of the long-duration gamma-ray burst GRB 230328B, combining prompt gamma-ray observations with exceptionally early simultaneous optical photometry and extensive X-ray, radio, and host-galaxy follow-up. NUTTELA- TAO began simultaneous g'r'i' observations only 41 s after the Swift/BAT trigger, corresponding to approximately 16 s in the rest frame for the adopted host-galaxy photometric redshift of z_phot = 1.54+-0.06. Unlike sequential multiband measurements, these observations provide an instantaneous optical spectral slope without temporal-interpolation uncertainties. The early optical continuum remains statistically consistent with a constant slope from approximately 10^2 to 7*10^3 s, providing no evidence for rapid dust destruction. The absence of significant color evolution across the pronounced optical rebrightening at approximately 4*10^3 s demonstrates that it is achromatic and favours a dynamical rather than spectral origin. Broadband modelling shows that the optical, X-ray, and radio evolution can be broadly explained by forward-shock emission with late energy injection, although alternative scenarios cannot be excluded. The red optical continuum is consistent with substantial line-of-sight extinction in a massive, dusty host galaxy. Late-time observations are insufficient to constrain a typical GRB-associated supernova at the adopted redshift. GRB 230328B therefore provides a benchmark for connecting the earliest simultaneous optical colors with afterglow dynamics and the host environment of a representative long GRB.
Versions
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BibTeX
@misc{komesh2026earliest,
title = {{Earliest simultaneous multi-color optical observations of GRB 230328B: from 41 seconds to the host-galaxy identification}},
author = {T. Komesh and A. Pozanenko and N. Pankov and A. Volnova and P. Minaev and R. Gill and D. Berdikhan and B. Grossan and Z. Maksut and Z. Abdullayev and S. Belkin and M. Krugov and A. Moskvitin and K. Baigarin and A. Tursynkan and E. Klunko and A. Tatarnikov and S. Zheltoukhov and V. Rumyantsev and A. Volvach and L. Volvach and O. A. Burkhonov and S. A. Ehgamberdiev and R. Inasaridze and L. Elenin and A. Krylov and M. Zheltobryukhov and S. B. Pandey and A. K. Ror and R. Gupta and V. Swain and V. Bhalerao and G. C. Anupama and S. Barway and R. Sánchez-Ramírez and A. J. Castro-Tirado and S. Antier and P. Beniamini and E. Abdikamalov},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2606.04585},
eprint = {2606.04585},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.04585},
}
RIS
TY - UNPB
TI - Earliest simultaneous multi-color optical observations of GRB 230328B: from 41 seconds to the host-galaxy identification
AU - T. Komesh
AU - A. Pozanenko
AU - N. Pankov
AU - A. Volnova
AU - P. Minaev
AU - R. Gill
AU - D. Berdikhan
AU - B. Grossan
AU - Z. Maksut
AU - Z. Abdullayev
AU - S. Belkin
AU - M. Krugov
AU - A. Moskvitin
AU - K. Baigarin
AU - A. Tursynkan
AU - E. Klunko
AU - A. Tatarnikov
AU - S. Zheltoukhov
AU - V. Rumyantsev
AU - A. Volvach
AU - L. Volvach
AU - O. A. Burkhonov
AU - S. A. Ehgamberdiev
AU - R. Inasaridze
AU - L. Elenin
AU - A. Krylov
AU - M. Zheltobryukhov
AU - S. B. Pandey
AU - A. K. Ror
AU - R. Gupta
AU - V. Swain
AU - V. Bhalerao
AU - G. C. Anupama
AU - S. Barway
AU - R. Sánchez-Ramírez
AU - A. J. Castro-Tirado
AU - S. Antier
AU - P. Beniamini
AU - E. Abdikamalov
PY - 2026
DA - 2026/08/21
PB - arXiv
DO - 10.48550/arxiv.2606.04585
UR - https://arxiv.org/abs/2606.04585
AB - We present a multiwavelength study of the long-duration gamma-ray burst GRB 230328B, combining prompt gamma-ray observations with exceptionally early simultaneous optical photometry and extensive X-ray, radio, and host-galaxy follow-up. NUTTELA- TAO began simultaneous g'r'i' observations only 41 s after the Swift/BAT trigger, corresponding to approximately 16 s in the rest frame for the adopted host-galaxy photometric redshift of z_phot = 1.54+-0.06. Unlike sequential multiband measurements, these observations provide an instantaneous optical spectral slope without temporal-interpolation uncertainties. The early optical continuum remains statistically consistent with a constant slope from approximately 10^2 to 7*10^3 s, providing no evidence for rapid dust destruction. The absence of significant color evolution across the pronounced optical rebrightening at approximately 4*10^3 s demonstrates that it is achromatic and favours a dynamical rather than spectral origin. Broadband modelling shows that the optical, X-ray, and radio evolution can be broadly explained by forward-shock emission with late energy injection, although alternative scenarios cannot be excluded. The red optical continuum is consistent with substantial line-of-sight extinction in a massive, dusty host galaxy. Late-time observations are insufficient to constrain a typical GRB-associated supernova at the adopted redshift. GRB 230328B therefore provides a benchmark for connecting the earliest simultaneous optical colors with afterglow dynamics and the host environment of a representative long GRB.
ER -