A Multiwavelength View of the First Type Ic-BL Supernova with an Einstein Probe X-Ray Shock Breakout
Year: 2026
Type: article
Abstract: In 2026 March, the Einstein Probe (EP) discovered its nearest ( z = 0.0343) Fast X-ray Transient (FXT), EP 260321a, the first EP FXT to provide a strong match to expectations for X-ray “shock breakout” (SBO) emission. Here, we present our multiwavelength follow-up campaign of EP 260321a and its broad-line Type Ic (Ic-BL) supernova (SN) counterpart, SN 2026gzf. We show that our radio follow-up extending over 5.8–54.5 days post-FXT rules out an on-axis jet counterpart of isotropic-equivalent kinetic energy E K ≳ 10 49 erg for circumburst densities n > 10 −2 cm −3 and assuming microphysical parameters ϵ e = ϵ B = 0.1. Our radio data also constrain a median mass-loss rate of M ̇ ≲ 1.2 × 1 0 − 5 M ⊙ yr − 1 for a Wolf–Rayet progenitor. In addition, we derive SN 2026gzf’s properties, including 56 Ni mass, diffusion timescale, and expansion velocities, from our ∼nightly cadence optical data and compare them with those of optically discovered Type Ic-BL SNe, finding that SN 2026gzf is well within the 90% confidence interval across all properties. We further fit SN 2026gzf’s light curve and determine that combined emission from both interaction with CSM and 56 Ni radioactive decay provides the best fit with plausible model parameters. Finally, using the rate of Ic-BL SNe from the Zwicky Transient Facility Bright Transient Survey and assuming all Type Ic-BL SNe produce EP 260321a-like FXTs, we infer an expected rate of EP-detected SBOs of 4.4–16 yr −1 . This is inconsistent at the 90% confidence level with current EP detection rates, potentially indicating that most Type Ic-BL SNe produce less luminous X-ray SBO signals compared to EP 260321a.
Authors: Jillian C. Rastinejad, Gokul Srinivasaragavan, Nikhil Sarin, Tanner O’Dwyer, S. Bradley Cenko, James K. Leung, Anya E. Nugent, Daniel A. Perley, Genevieve Schroeder, Shreya Anand, Tomás Ahumada, Igor Andreoni, Aleksandra Bochenek, Alessandra Corsi, Christoffer Fremling, Anna Y. Q. Ho, Mansi M. Kasliwal, Geoffrey Mo, Anirudh Salgundi, Kendall I. Sippy, J. Sollerman, Eric C. Bellm, Tracy X. Chen, Michael W. Coughlin, Michael C. Davis, Fabio De Colle, Danielle Frostig, Christopher L. Fryer, Michael J. Graham, Xander J. Hall, K.-R. Hinds, Luca Izzo, Wynn Jacobson-Galán, Nathan P. Lourie, Keiichi Maeda, Josiah Purdum, Ben Rusholme, Avinash Singh, Robert Stein
Institutions: University of Maryland, College Park, California Institute of Technology, Goddard Space Flight Center, University of Cambridge, Johns Hopkins University, George Washington University, University of Toronto, Hebrew University of Jerusalem, Center for Astrophysics Harvard & Smithsonian, Liverpool John Moores University, Cornell University, Stanford University, Cerro Tololo Inter-American Observatory, NSF NOIRLab, University of North Carolina at Chapel Hill, Carnegie Institution for Science, Pennsylvania State University, Stockholm University, University of Washington, University of Minnesota, Universidad Nacional Autónoma de México, Los Alamos National Laboratory, Carnegie Mellon University, University of Copenhagen, Astronomical Observatory of Capodimonte, Massachusetts Institute of Technology, Kyoto University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,400
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, John Templeton Foundation, Gordon and Betty Moore Foundation, Research Corporation for Science Advancement, California Institute of Technology, University of Washington, Drexel University, Research Corporation for Scientific Advancement, Space Telescope Science Institute, Institute of Science and Technology Austria, Hebrew University of Jerusalem, University of Toronto, Korea Astronomy and Space Science Institute, Knut och Alice Wallenbergs Stiftelse, Liverpool John Moores University, National Central University, Ministério da Ciência, Tecnologia, Inovações e Comunicações, Agencia Nacional de Investigación y Desarrollo, Office of Science, University of North Carolina at Chapel Hill, Science and Technology Facilities Council, Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México, SLAC National Accelerator Laboratory
Awards: G1229526393, NSF's National Optical-Infrared Astronomy Research Laboratory (NOIRLab): Management and Operations of Vera C. Rubin Observatory, The SED Machine: an Efficient Transient Classifier, Postdoctoral Fellowship: AAPF: The explosive origins of heavy elements: systematic searches for r-process sites with WINTER, Construction of Vera C. Rubin Observatory under the Major Research Equipment and Facilities Construction (MREFC) Account, G206958410, Final Design, Construction and Operations of Vera C. Rubin Observatory, G2318220113, G2371548206, G2384795368, G262532246, G2720911013, G303061748, Extending the Teach of Gravitational-Wave Detectors through Low Latency Data Products, Unmodeled Searches, and Detector Characterization, G336187100, G4235786860, G433322167, Collaborative Research: New Windows on the Dynamic Universe with the Vera C. Rubin Observatory, the InterPlanetary Network, and the International Gravitational Wave Network, G4654690619, NSF's National Optical-Infrared Astronomy Research Laboratory (NOIRLab) as a Federally Funded Research and Development Center (FFRDC), DFG-NSF Physics: Maximizing the Science Return of Target of Opportunity Observations Connected to Compact Binary Mergers, G495301720, G498139845, G5473946529, G5570207115, G58316358, Enabling Synergistic Science between the Rubin Observatory and the Zwicky Transient Facility, CDS&E: Collaborative Research: Development and Application of Machine Learning Classification of Optical Transients, G6273510985, Imaging of the interaction between Engineered Nano-materials and Model Liposomes, Elucidating Desert Microbial Strategies for Critical Material Acquisition through Spatial Metabolomics and Multi-Omics, HDR Institute: Accelerated AI Algorithms for Data-Driven Discovery, Collaborative Research: New Windows on the Dynamic Universe with the Vera C. Rubin Observatory, the InterPlanetary Network, and the International Gravitational Wave Network, G7938408761, G8100935542, G8382000481, G8726098666, CDS&E: Enabling Population Studies of Supernovae in the Era of Vera Rubin via Simulated-based Inference, Establishing a Templeton LSST Early-Career Research Fellowship, G969889393
OpenAlex ID: W7172525334