Multiwavelength analysis of AT 2023sva: a luminous orphan afterglow with evidence for a structured jet

ABSTRACT We present multiwavelength analysis of ZTF23abelseb (AT 2023sva), an optically discovered fast-fading ($\Delta m_r = 2.2$ mag in $\Delta t = 0.74$ d), luminous ($M_r \sim -30.0$ mag), and red ($g-r = 0.50$ mag) transient at $z = 2.28$ with accompanying luminous radio emission. AT 2023sva does not possess a $\gamma$-ray burst (GRB) counterpart to an isotropic equivalent energy limit of $E_{\rm {\gamma , \, iso}} \lt 1.6 \times 10^{52}$ erg, determined through searching $\gamma$-ray satellite archives between the last non-detection and first detection, making it the sixth example of an optically discovered afterglow with a redshift measurement and no detected GRB counterpart. We analyse AT 2023sva’s optical, radio, and X-ray observations to characterize the source. From radio analyses, we find the clear presence of strong interstellar scintillation (ISS) 72 d after the initial explosion, allowing us to place constraints on the source’s angular size and bulk Lorentz factor. When comparing the source sizes derived from ISS of orphan events to those of the classical GRB population, we find orphan events have statistically smaller source sizes. We also utilize Bayesian techniques to model the multiwavelength afterglow. Within this framework, we find evidence that AT 2023sva possesses a shallow power-law structured jet viewed slightly off-axis ($\theta _{\rm {v}} = 0.07 \pm 0.02$) just outside of the jet’s core opening angle ($\theta _{\rm {c}} = 0.06 \pm 0.02$). We determine this is likely the reason for the lack of a detected GRB counterpart, but also investigate other scenarios. AT 2023sva’s evidence for possessing a structured jet stresses the importance of broadening orphan afterglow search strategies to a diverse range of GRB jet angular energy profiles, to maximize the return of future optical surveys.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-02-18
DOI
https://doi.org/10.1093/mnras/staf290
Citations
7
Primary Topic
Gamma-ray bursts and supernovae
Type
article
Field-Weighted Citation Impact
8.08

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article

Multiwavelength analysis of AT 2023sva: a luminous orphan afterglow with evidence for a structured jet

Avery Wold, J. F. Agüí Fernández, Lauren Rhodes, Jacob Wise et al.
7 citations
Monthly Notices of the Royal Astronomical Society
Gamma-ray bursts and supernovae
8.08
article

Multiwavelength analysis of AT 2023sva: a luminous orphan afterglow with evidence for a structured jet

Avery Wold, J. F. Agüí Fernández, Lauren Rhodes, Jacob Wise, Niharika Sravan, Sudhanshu Barway, Gokul P. Srinivasaragavan, M. Coleman Miller, R. P. Fender, A. de Ugarte Postigo, V. Bhalerao, Maggie L. Li, J. Sollerman, Anirudh Salgundi, Vishwajeet Swain, A. Ridnaia, A. Tsvetkova, M. J. Graham, M. Ulanov, D. Malesani, P. Chandra, Harsh Kumar, Josiah Purdum, Brendan O’Connor, G. Waratkar, A. J. Drake, D. Frederiks, D. Svinkin, G. C. Anupama, Russ R. Laher, S. R. Kulkarni, D. A. Perley, S. B. Cenko, M. W. Coughlin, Anna Y. Q. Ho, Eric C. Bellm, A. Lysenko, David A. Green, C. C. Thöne, Geoffrey Ryan, Maria Babakhanyan Stone, Eric Burns, R. A. Perley, Tomás Ahumada, Nikhil Sarin, Roger M. Smith, M. M. Kasliwal, David Titterington, A. J. Nayana, Jada L. Vail, S. Geier, Suryansh Srijan, Gopal Parwani
article en
7 citations

Abstract

ABSTRACT We present multiwavelength analysis of ZTF23abelseb (AT 2023sva), an optically discovered fast-fading ($\Delta m_r = 2.2$ mag in $\Delta t = 0.74$ d), luminous ($M_r \sim -30.0$ mag), and red ($g-r = 0.50$ mag) transient at $z = 2.28$ with accompanying luminous radio emission. AT 2023sva does not possess a $\gamma$-ray burst (GRB) counterpart to an isotropic equivalent energy limit of $E_{\rm {\gamma , \, iso}} \lt 1.6 \times 10^{52}$ erg, determined through searching $\gamma$-ray satellite archives between the last non-detection and first detection, making it the sixth example of an optically discovered afterglow with a redshift measurement and no detected GRB counterpart. We analyse AT 2023sva’s optical, radio, and X-ray observations to characterize the source. From radio analyses, we find the clear presence of strong interstellar scintillation (ISS) 72 d after the initial explosion, allowing us to place constraints on the source’s angular size and bulk Lorentz factor. When comparing the source sizes derived from ISS of orphan events to those of the classical GRB population, we find orphan events have statistically smaller source sizes. We also utilize Bayesian techniques to model the multiwavelength afterglow. Within this framework, we find evidence that AT 2023sva possesses a shallow power-law structured jet viewed slightly off-axis ($\theta _{\rm {v}} = 0.07 \pm 0.02$) just outside of the jet’s core opening angle ($\theta _{\rm {c}} = 0.06 \pm 0.02$). We determine this is likely the reason for the lack of a detected GRB counterpart, but also investigate other scenarios. AT 2023sva’s evidence for possessing a structured jet stresses the importance of broadening orphan afterglow search strategies to a diverse range of GRB jet angular energy profiles, to maximize the return of future optical surveys.

Monthly Notices of the Royal Astronomical SocietyVol. 538(1)
Tata Institute of Fundamental Research (IN), Nordic Institute for Theoretical Physics (SE), Louisiana State University (US), California Institute of Technology (US), University of Copenhagen (DK), Space Science Institute (US), University of Minnesota (US), Goddard Space Flight Center (US), Indian Institute of Astrophysics (IN), Radboud University Nijmegen (NL), National Centre for Radio Astrophysics (IN), University of Turku (FI), Stockholm University (SE), Indian Institute of Technology Bombay (IN), University of Cagliari (IT), Perimeter Institute (CA), University of Washington (US), Cornell University (US), Aix-Marseille Université (FR), University of Cambridge (GB), National Radio Astronomy Observatory (US), Czech Academy of Sciences, Astronomical Institute (CZ), University of Oxford (GB), Calar Alto Observatory (ES), DAWN Center for Independent Living (US), Joint Space Science Institute (US), Center for Astrophysics Harvard & Smithsonian (US), Observatoire de la Côte d’Azur (FR), Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari (IT), Instituto de Astrofísica de Canarias (ES), AlbaNova (SE), Gran Telescopio Canarias (Spain) (ES), Infrared Processing and Analysis Center (US), Deleted Institution, City University of Seattle (US), McGill University (CA), Liverpool John Moores University (GB), University of Maryland, College Park (US), Drexel University (US), Carnegie Mellon University (US), KTH Royal Institute of Technology (SE), Ioffe Institute (RU)
National Science Foundation, National Aeronautics and Space Administration, University of Wisconsin-Madison, Northwestern University, University of Maryland, American Sheep Industry Association, University of Warwick, Trinity College Dublin, European School of Oncology, Suomen Kulttuurirahasto, Stockholms Universitet, Institut sur la Nutrition et les Aliments Fonctionnels, Science and Technology Facilities Council
Openalex Percentile: Top 3%
Gamma-ray bursts and supernovae
8.08
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