Circumstellar interaction in the extreme white dwarf merger remnant ZTF J1901+1458
Rattachement africain : at, us, au, de, es, ca, sk, gb. Niveau de preuve : code pays fourni par la source.
Le résumé fourni par la source
Double-degenerate white dwarf (WD) merger remnants can exhibit extreme magnetic fields exceeding 108 G and rapid rotation, but their spectral energy distributions and high-energy emission mechanisms remain poorly characterised. ZTF J1901+1458 stands out as the most compact and strongly magnetised object discovered in this class to date. Intriguingly, recent Chandra observations have revealed that the white dwarf is also a source of soft X-ray emission that is too bright and hard to be of photospheric origin. We analysed new phase-resolved ultraviolet (UV) spectroscopy from the Hubble Space Telescope, together with optical and near-infrared photometry and spectroscopy, using new magnetic atmosphere models to determine its effective temperature, radius, mass, average surface magnetic-field strength, and cooling age. The spectral break at ≈3000 Å, observed in several highly magnetised WDs, is well reproduced by our new models, which account for the effect of magnetic opacities on the atmospheric structure. Our best-fit parameters for the WD yield a cooler effective temperature ($ T_{\mathrm{eff}}=27,445^{+680}_{-1390} $ K) and a larger radius than previously reported. Furthermore, the near-infrared data exclude the presence of a stellar or brown dwarf companion hotter than ≈700 K. We jointly analysed published Chandra/Advanced CCD Imaging Spectrometer Imaging array (ACIS-I) data and new XMM-Newton/European Photon Imaging Camera (EPIC) X-ray spectra. The faint X-ray emission, LX = (1.44 ± 0.13)×1027 erg s−1, is highly pulsed at the rotation period of the WD, and the soft spectrum can be modelled by a power-law model with photon index $ \Gamma=2.43^{+0.17}_{-0.15} $. We suggest that the X-rays are powered by accretion or by interaction between the WD magnetosphere and circumstellar material. A rapidly rotating magnetic field could power a weak wind along open field lines and extract material from the surface of the WD. Alternatively, low-level accretion of fallback material from the past merger event or the tidal disruption of a planetary body could supply the circumstellar material.
Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.
Le contrôle bibliographique ouvert
Où se fait cette recherche
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Institute of Science and Technology Austria pays non établi dans la noticeUniversité ou école supérieure
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California Institute of Technology Mailcode 350-17 pays non établi dans la noticeUniversité ou école supérieure
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Australian National University Mathematical Sciences Institute pays non établi dans la noticeUniversité ou école supérieure
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Australian Mathematical Sciences Institute pays non établi dans la noticeInstitution
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International Centre for Radio Astronomy Research pays non établi dans la noticeInstitution
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Center for Astrophysics Harvard & Smithsonian pays non établi dans la noticeUniversité ou école supérieure
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Leibniz Institute for Astrophysics Potsdam pays non établi dans la noticeStructure de recherche
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Universitat Politècnica de Catalunya pays non établi dans la noticeUniversité ou école supérieure
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Boston University Department of Astronomy pays non établi dans la noticeUniversité ou école supérieure
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University of British Columbia Department of Physics and Astronomy pays non établi dans la noticeUniversité ou école supérieure
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Astronomical Institute of the Slovak Academy of Sciences pays non établi dans la noticeStructure de recherche
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Massachusetts Institute of Technology Department of Physics pays non établi dans la noticeUniversité ou école supérieure
Institute of Science and Technology Austria, Mailcode 350-17 — California Institute of Technology et Mathematical Sciences Institute — Australian National University, avec 9 autres affiliations.
Une affiliation ne permet pas de déduire la nationalité d’un auteur.