A half ring of ionized circumstellar material trapped in the magnetosphere of a white dwarf merger remnant
Year: 2026
Type: article
Abstract: Many white dwarfs are observed in compact double white dwarf binaries, and through the emission of gravitational waves, a large fraction are destined to merge. The merger remnants that do not explode in a Type Ia supernova are expected to initially be rapidly rotating and highly magnetized. In this work, we present our discovery of the variable white dwarf ZTF J200832.79+444939.67, hereafter ZTF J2008+4449, as a likely merger remnant showing signs of circumstellar material without a stellar or substellar companion. The nature of ZTF J2008+4449 as a merger remnant is supported by its physical properties: it is hot (35 500 ± 300 K) and massive (1.12 ± 0.03 M⊙), rapidly rotating with a period of ≈6.6 minutes, and likely possesses exceptionally strong magnetic fields (∼400−600 MG) at its surface. Remarkably, we detect a significant period derivative of (1.80 ± 0.09)×10−12 s/s, indicating that the white dwarf is spinning down, and a soft X-ray emission that is inconsistent with photospheric emission. As the presence of a mass-transferring stellar or brown dwarf companion is excluded by infrared photometry, the detected spin-down and X-ray emission could be tell-tale signs of a magnetically driven wind or of interaction with circumstellar material, possibly originating from the fallback of gravitationally bound merger ejecta or from the tidal disruption of a planetary object. We also detect Balmer emission, which requires the presence of ionized hydrogen in the vicinity of the white dwarf, showing Doppler shifts as high as ≈2000 km s−1. The unusual variability of the Balmer emission on the spin period of the white dwarf is consistent with the trapping of a half ring of ionized gas in the magnetosphere of the white dwarf.
Authors: Andrei A. Cristea, Ilaria Caiazzo, Tim Cunningham, John C. Raymond, Stephane Vennes, Adela Kawka, Aayush Desai, David R. Miller, J. J. Hermes, Jim Fuller, Jeremy Heyl, Jan van Roestel, Kevin B. Burdge, Antonio C. Rodriguez, Ingrid Pelisoli, Boris T. Gänsicke, Paula Szkody, Scott J. Kenyon, Zach Vanderbosch, Andrew Drake, Lilia Ferrario, Dayal Wickramasinghe, Viraj R. Karambelkar, Stephen Justham, Ruediger Pakmor, Kareem El-Badry, Thomas Prince, S. R. Kulkarni, Matthew J. Graham, Frank J. Masci, Steven L. Groom, Josiah Purdum, Richard Dekany, Eric C. Bellm
Institutions: Institute of Science and Technology Austria, California Institute of Technology, Center for Astrophysics Harvard & Smithsonian, Australian National University, Curtin University, International Centre for Radio Astronomy Research, University of British Columbia, University of Amsterdam, Massachusetts Institute of Technology, University of Warwick, University of Washington, Max Planck Institute for Astrophysics, Infrared Processing and Analysis Center, Boston University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, California Institute of Technology, University of Washington, Johns Hopkins University, Drexel University, Space Telescope Science Institute, Institute of Science and Technology Austria, European Space Agency, European Commission, Queen's University Belfast, Durham University, Queen's University, National Central University, Eötvös Loránd Tudományegyetem, Max-Planck-Institut für Astronomie, University of North Carolina at Chapel Hill, Smithsonian Astrophysical Observatory, Science Mission Directorate, Planetary Science Division, Los Alamos National Laboratory
Awards: G103270039, G1927429072, G2171960263, G256731684, Exploring & Exploiting the Dynamic Optical Sky, ZWICKY TRANSIENT FACILITY, G433322167, G4474636675, G492514714, G58316358, Enabling Synergistic Science between the Rubin Observatory and the Zwicky Transient Facility, G618131832, G6273510985, A NEO SEARCH PROGRAM USING THE PAN-STARRS PS1 TELESCOPETHE GOAL OF THE PROPOSED RESEARCH IS TO USE T, G6972301876, G7187964967, Pan-STARRS1: Operations; Public Data Release; Education and Outreach, G833430883
OpenAlex ID: W7122851263
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