---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21274'
abstract:
- lang: eng
  text: "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\r\n                    <jats:sub>⊙</jats:sub>\r\n                    ),
    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\r\n                    <jats:sup>−12</jats:sup>\r\n
    \                   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\r\n                    <jats:sup>−1</jats:sup>\r\n
    \                   . 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.\r\n                  </jats:p>"
acknowledgement: "We thank Lynne Hillenbrand and Soumyadeep Bhattacharjee for helpful
  discussions, and Kishalay De for his help with the WIRC\r\nreduction pipeline. IC
  was supported by NASA through grants from the Space\r\nTelescope Science Institute,
  under NASA contracts NASA.22K1813, NAS5-\r\n26555 and NAS5-03127. TC was supported
  by NASA through the NASA Hubble\r\nFellowship grant HST-HF2-51527.001-A awarded
  by the Space Telescope Science Institute, which is operated by the Association of
  Universities for Research\r\nin Astronomy, Inc., for NASA, under contract NAS5-26555.
  This project has\r\nreceived funding from the European Research Council (ERC) under
  the European Union’s Horizon 2020 research and innovation programme (Grant agreement
  No. 101020057). This work was based on observations obtained with the\r\nSamuel
  Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar\r\nObservatory
  as part of the Zwicky Transient Facility project. ZTF is supported\r\nby the National
  Science Foundation under Grants No. AST-1440341, AST2034437, and currently Award
  #2407588. ZTF receives additional funding from\r\nthe ZTF partnership. Current members
  include Caltech, USA; Caltech/IPAC,\r\nUSA; University of Maryland, USA; University
  of California, Berkeley, USA;\r\nUniversity of Wisconsin at Milwaukee, USA; Cornell
  University, USA; Drexel\r\nUniversity, USA; University of North Carolina at Chapel
  Hill, USA; Institute\r\nof Science and Technology, Austria; National Central University,
  Taiwan, and\r\nOKC, University of Stockholm, Sweden. Operations are conducted by
  Caltech’s\r\nOptical Observatory (COO), Caltech/IPAC, and the University of Washington
  at\r\nSeattle, USA. This work has made use of data from the European Space Agency\r\n(ESA)
  mission Gaia (https://www.cosmos.esa.int/gaia), processed by\r\nthe Gaia Data Processing
  and Analysis Consortium (DPAC, https://www.\r\ncosmos.esa.int/web/gaia/dpac/consortium).
  Funding for the DPAC has been provided by national institutions, in particular the
  institutions participating in the Gaia Multilateral Agreement. The Pan-STARRS1 Surveys
  (PS1)\r\nand the PS1 public science archive have been made possible through contributions
  by the Institute for Astronomy, the University of Hawaii, the PanSTARRS Project
  Office, the Max-Planck Society and its participating institutes, the Max Planck
  Institute for Astronomy, Heidelberg and the Max Planck\r\nInstitute for Extraterrestrial
  Physics, Garching, The Johns Hopkins University,\r\nDurham University, the University
  of Edinburgh, the Queen’s University Belfast,\r\nthe Harvard-Smithsonian Center
  for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated,
  the National Central University of Taiwan, the Space Telescope Science Institute,
  the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued
  through\r\nthe Planetary Science Division of the NASA Science Mission Directorate,
  the\r\nNational Science Foundation Grant No. AST–1238877, the University of Maryland,
  Eotvos Lorand University (ELTE), the Los Alamos National Laboratory,\r\nand the
  Gordon and Betty Moore Foundation. This work made use of Astropy\r\n(http://www.astropy.org):
  a community-developed core Python package\r\nand an ecosystem of tools and resources
  for astronomy (Astropy Collaboration\r\n2013, 2018, 2022)."
article_number: A188
article_processing_charge: Yes
article_type: original
author:
- first_name: Andrei-Alexandru
  full_name: Cristea, Andrei-Alexandru
  id: 4d500bea-31f8-11ee-a48d-d4904fb363c7
  last_name: Cristea
- first_name: Ilaria
  full_name: Caiazzo, Ilaria
  id: 8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d
  last_name: Caiazzo
  orcid: 0000-0002-4770-5388
- first_name: Tim
  full_name: Cunningham, Tim
  last_name: Cunningham
- first_name: John C.
  full_name: Raymond, John C.
  last_name: Raymond
- first_name: Stephane
  full_name: Vennes, Stephane
  last_name: Vennes
- first_name: Adela
  full_name: Kawka, Adela
  last_name: Kawka
- first_name: Aayush A
  full_name: Desai, Aayush A
  id: 502cfd30-32c1-11ee-a9a4-d8dad5c6739e
  last_name: Desai
- first_name: David R.
  full_name: Miller, David R.
  last_name: Miller
- first_name: J. J.
  full_name: Hermes, J. J.
  last_name: Hermes
- first_name: Jim
  full_name: Fuller, Jim
  last_name: Fuller
- first_name: Jeremy
  full_name: Heyl, Jeremy
  last_name: Heyl
- first_name: Jan
  full_name: van Roestel, Jan
  last_name: van Roestel
- first_name: Kevin B.
  full_name: Burdge, Kevin B.
  last_name: Burdge
- first_name: Antonio C.
  full_name: Rodriguez, Antonio C.
  last_name: Rodriguez
- first_name: Ingrid
  full_name: Pelisoli, Ingrid
  last_name: Pelisoli
- first_name: Boris T.
  full_name: Gänsicke, Boris T.
  last_name: Gänsicke
- first_name: Paula
  full_name: Szkody, Paula
  last_name: Szkody
- first_name: Scott J.
  full_name: Kenyon, Scott J.
  last_name: Kenyon
- first_name: Zach
  full_name: Vanderbosch, Zach
  last_name: Vanderbosch
- first_name: Andrew
  full_name: Drake, Andrew
  last_name: Drake
- first_name: Lilia
  full_name: Ferrario, Lilia
  last_name: Ferrario
- first_name: Dayal
  full_name: Wickramasinghe, Dayal
  last_name: Wickramasinghe
- first_name: Viraj R.
  full_name: Karambelkar, Viraj R.
  last_name: Karambelkar
- first_name: Stephen
  full_name: Justham, Stephen
  last_name: Justham
- first_name: Ruediger
  full_name: Pakmor, Ruediger
  last_name: Pakmor
- first_name: Kareem
  full_name: El-Badry, Kareem
  last_name: El-Badry
- first_name: Thomas
  full_name: Prince, Thomas
  last_name: Prince
- first_name: S. R.
  full_name: Kulkarni, S. R.
  last_name: Kulkarni
- first_name: Matthew J.
  full_name: Graham, Matthew J.
  last_name: Graham
- first_name: Frank J.
  full_name: Masci, Frank J.
  last_name: Masci
- first_name: Steven L.
  full_name: Groom, Steven L.
  last_name: Groom
- first_name: Josiah
  full_name: Purdum, Josiah
  last_name: Purdum
- first_name: Richard
  full_name: Dekany, Richard
  last_name: Dekany
- first_name: Eric C.
  full_name: Bellm, Eric C.
  last_name: Bellm
citation:
  ama: Cristea A-A, Caiazzo I, Cunningham T, et al. A half ring of ionized circumstellar
    material trapped in the magnetosphere of a white dwarf merger remnant. <i>Astronomy
    &#38; Astrophysics</i>. 2026;706. doi:<a href="https://doi.org/10.1051/0004-6361/202556432">10.1051/0004-6361/202556432</a>
  apa: Cristea, A.-A., Caiazzo, I., Cunningham, T., Raymond, J. C., Vennes, S., Kawka,
    A., … Bellm, E. C. (2026). A half ring of ionized circumstellar material trapped
    in the magnetosphere of a white dwarf merger remnant. <i>Astronomy &#38; Astrophysics</i>.
    EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/202556432">https://doi.org/10.1051/0004-6361/202556432</a>
  chicago: Cristea, Andrei-Alexandru, Ilaria Caiazzo, Tim Cunningham, John C. Raymond,
    Stephane Vennes, Adela Kawka, Aayush A Desai, et al. “A Half Ring of Ionized Circumstellar
    Material Trapped in the Magnetosphere of a White Dwarf Merger Remnant.” <i>Astronomy
    &#38; Astrophysics</i>. EDP Sciences, 2026. <a href="https://doi.org/10.1051/0004-6361/202556432">https://doi.org/10.1051/0004-6361/202556432</a>.
  ieee: A.-A. Cristea <i>et al.</i>, “A half ring of ionized circumstellar material
    trapped in the magnetosphere of a white dwarf merger remnant,” <i>Astronomy &#38;
    Astrophysics</i>, vol. 706. EDP Sciences, 2026.
  ista: Cristea A-A, Caiazzo I, Cunningham T, Raymond JC, Vennes S, Kawka A, Desai
    AA, Miller DR, Hermes JJ, Fuller J, Heyl J, van Roestel J, Burdge KB, Rodriguez
    AC, Pelisoli I, Gänsicke BT, Szkody P, Kenyon SJ, Vanderbosch Z, Drake A, Ferrario
    L, Wickramasinghe D, Karambelkar VR, Justham S, Pakmor R, El-Badry K, Prince T,
    Kulkarni SR, Graham MJ, Masci FJ, Groom SL, Purdum J, Dekany R, Bellm EC. 2026.
    A half ring of ionized circumstellar material trapped in the magnetosphere of
    a white dwarf merger remnant. Astronomy &#38; Astrophysics. 706, A188.
  mla: Cristea, Andrei-Alexandru, et al. “A Half Ring of Ionized Circumstellar Material
    Trapped in the Magnetosphere of a White Dwarf Merger Remnant.” <i>Astronomy &#38;
    Astrophysics</i>, vol. 706, A188, EDP Sciences, 2026, doi:<a href="https://doi.org/10.1051/0004-6361/202556432">10.1051/0004-6361/202556432</a>.
  short: A.-A. Cristea, I. Caiazzo, T. Cunningham, J.C. Raymond, S. Vennes, A. Kawka,
    A.A. Desai, D.R. Miller, J.J. Hermes, J. Fuller, J. Heyl, J. van Roestel, K.B.
    Burdge, A.C. Rodriguez, I. Pelisoli, B.T. Gänsicke, P. Szkody, S.J. Kenyon, Z.
    Vanderbosch, A. Drake, L. Ferrario, D. Wickramasinghe, V.R. Karambelkar, S. Justham,
    R. Pakmor, K. El-Badry, T. Prince, S.R. Kulkarni, M.J. Graham, F.J. Masci, S.L.
    Groom, J. Purdum, R. Dekany, E.C. Bellm, Astronomy &#38; Astrophysics 706 (2026).
corr_author: '1'
date_created: 2026-02-17T08:12:05Z
date_published: 2026-02-10T00:00:00Z
date_updated: 2026-04-28T12:01:21Z
day: '10'
ddc:
- '520'
department:
- _id: IlCa
- _id: GradSch
doi: 10.1051/0004-6361/202556432
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fulldoi: https://doi.org/10.1051/0004-6361/202556432
has_accepted_license: '1'
intvolume: '       706'
language:
- iso: eng
month: '02'
oa: 1
oa_version: Published Version
publication: Astronomy & Astrophysics
publication_identifier:
  eissn:
  - 1432-0746
  issn:
  - 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
related_material:
  link:
  - description: News on ISTA website
    relation: press_release
    url: https://ista.ac.at/en/news/twos-company-new-class-of-star-remnants/
status: public
title: A half ring of ionized circumstellar material trapped in the magnetosphere
  of a white dwarf merger remnant
tmp:
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type: journal_article
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