Статья

Swift spectra of AT2018cow: a white dwarf tidal disruption event?

N. P. M. KuinMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UKKinwah WuMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UKS. R. OatesDepartment of Physics, University of Warwick, Coventry CV4 7AL, UKA. Y. LienCenter for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, MD 20771, USAS. W. K. EmeryMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UKJ. A. KenneaDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAM. de PasqualeDepartment of Astronomy and Space Sciences, Istanbul University, Beyazit, 34119 Istanbul, TurkeyQin HanMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UKPeter J. BrownDepartment of Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX 77843, USAA. TohuvavohuDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAA. A. BreeveldMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UKD. N. BurrowsDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAS. B. CenkoAstrophysics Science Division, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USAS. CampanaINAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807, Merate, ItalyA. J. LevanDepartment of Physics, University of Warwick, Coventry CV4 7AL, UKC. B. MarkwardtAstrophysics Science Division, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USAJ. P. OsborneDepartment of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UKM. J. PageMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UKK. L. PageDepartment of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UKB. SbarufattiDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAM. H. SiegelDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAE. TrojaAstrophysics Science Division, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA

2019en

ABI

Аннотация

The bright transient AT2018cow has been unlike any other known type of transient. Its high brightness, rapid rise and decay and initially nearly featureless spectrum are unprecedented and difficult to explain using models for similar burst sources. We present evidence for faint -ray emission continuing for at least 8 days, and featureless spectra in the ultraviolet bands -both unusual for eruptive sources. The X-ray variability of the source has a burst-like character. The UV-optical spectrum does not show any CNO line but is well described by a blackbody. We demonstrate that a model invoking the tidal disruption of a 0.1 -0.4 M Helium White Dwarf (WD) by a 10 5 -10 6 M Black Hole (BH) located in the outskirts of galaxy Z 137-068 could provide an explanation for most of the characteristics shown in the multi-wavelength observations. A blackbody-like emission is emitted from an opaque photosphere, formed by the debris of the WD disruption. Broad features showing up in the optical/infrared spectra in the early stage are probably velocity broadened lines produced in a transient high-velocity outward moving cocoon. The asymmetric optical/infrared lines that appeared at a later stage are emission from an atmospheric layer when it detached from thermal equilibrium with the photosphere, which undergoes more rapid cooling. The photosphere shrinks when its temperature drops, and the subsequent infall of the atmosphere produced asymmetric line profiles. Additionally, a non-thermal jet might be present, emitting X-rays in the 10 -150 keV band.

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Идентификаторы

DOI: 10.1093/mnras/stz053

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