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A pulsating white dwarf in an eclipsing binary

Abstract

White dwarfs are the burnt-out cores of Sun-like stars and are the fate of 97 per cent of the stars in our Galaxy. The internal structure and composition of white dwarfs are hidden by their high gravities, which causes all elements apart from the lightest ones to settle out of their atmospheres. The most direct method of probing the inner structure of stars and white dwarfs in detail is via asteroseismology. Here we present a pulsating white dwarf in an eclipsing binary system, enabling us to place extremely precise constraints on the mass and radius of the white dwarf from the lightcurve, independent of the pulsations. This 0.325-solar-mass white dwarf—one member of the SDSS J115219.99+024814.4 system—will serve as a powerful benchmark with which to constrain empirically the core composition of low-mass stellar remnants and to investigate the effects of close binary evolution on the internal structure of white dwarfs.

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Fig. 1: Trailed spectrogram of the Hα line of SDSS J1152+0248.
Fig. 2: HiPERCAM high-speed lightcurves of SDSS J1152+0248 with model fits overplotted.
Fig. 3: SED of SDSS J1152+0248 (red points are GALEX, SDSS and UKIDSS measurements) with best-fit model spectrum (black line and blue squares).
Fig. 4: The pulsations of the cool white dwarf in SDSS J1152+0248.
Fig. 5: Constraints on the masses and radii of the white dwarfs in SDSS J1152+0248.

Data availability

The raw (https://bit.ly/2T5nDKn) and reduced (https://bit.ly/3a94M6E) X-shooter data presented in this paper are available from the European Southern Observatory. Raw and reduced HiPERCAM data are available from the Gran Telescopio Canarias here: https://bit.ly/2T5f9mu. These data can also be obtained from the corresponding author upon reasonable request.

Code availability

The X-Shooter reduction pipeline (version 3.2.0) is available at https://www.eso.org/sci/software/pipelines/xshooter/ and the HiPERCAM pipeline at https://github.com/HiPERCAM/hipercam. The lightcurve-fitting method is available at https://github.com/trmrsh/cpp-lcurve. The codes used to generate the plots presented in this paper are available from the corresponding author upon reasonable request.

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Acknowledgements

S.G.P. acknowledges the support of a Science and Technology Facilities Council Ernest Rutherford Fellowship. HiPERCAM and V.S.D. are funded by the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) under ERC-2013-ADG grant agreement number 340040 (HiPERCAM). Partial support for this work was provided by NASA K2 Cycle 6 Grant 80NSSC19K0162. A.G.I. acknowledges support from the Netherlands Organisation for Scientific Research. This work is based on observations made with the Gran Telescopio Canarias (programme ID GTC59-18B), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, on the island of La Palma, and also based on observations made with the European Southern Observatory telescopes at the La Silla Paranal Observatory under programme ID 097.D-0786.

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All authors contributed to the work presented in this paper. S.G.P. reduced all the spectroscopic and photometric data and carried out the SED fitting. S.G.P. and V.S.D. performed the Gran Telescopio Canarias observations. A.J.B. performed the radial-velocity and lightcurve fitting. S.P.L. wrote the Python code that implemented the Gaussian processes in the lightcurve fitting. V.S.D., S.P.L., T.R.M., S.G.P., E.B., M.J.D., M.J.G. and D.I.S. all contributed to the development and support of HiPERCAM. J.J.H. analysed the pulsations in the HiPERCAM lightcurves. A.G.I. investigated the internal structure of the white dwarfs and the evolution of the binary. All authors reviewed the manuscript.

Corresponding author

Correspondence to Steven G. Parsons.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Alejandro Córsico, Ingrid Pelisoli and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Parsons, S.G., Brown, A.J., Littlefair, S.P. et al. A pulsating white dwarf in an eclipsing binary. Nat Astron 4, 690–696 (2020). https://doi.org/10.1038/s41550-020-1037-z

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