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arXiv · 2410.11568

Serendipitous observation of a white dwarf companion to a JWST/MIRI coronagraphic calibrator

Alexander Venner·Mary Anne Limbach·Mathilde Mâlin·Simon Blouin·Anthony Boccaletti·Logan A. Pearce
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Abstract

We present the unplanned detection of a white dwarf companion to the star HD 218261 in mid-infrared (10-16 $\mu$m) observations with JWST/MIRI. This star was observed as a calibrator for coronagraphic observations of the exoplanet host HR 8799. HD 218261 B has only previously been detected by Gaia, and only in visible light. We confidently detect the companion in the mid-infrared, where it is less luminous than the primary by a factor of ~10$^4$. The visible and mid-infrared photometry are consistent with a white dwarf of $T_\text{eff}\approx10000$ K, $M\approx0.8 M_\odot$, though observation of its optical spectrum is required to precisely constrain its physical parameters. These results demonstrate that precise mid-infrared photometry of white dwarf companions to bright stars can be obtained with MIRI, opening up new possibilities for studying white dwarfs in close binaries.

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Alexander Venner, Mary Anne Limbach, Mathilde Mâlin, Simon Blouin, Anthony Boccaletti, Logan A. Pearce. 2024-10-15. Serendipitous observation of a white dwarf companion to a JWST/MIRI coronagraphic calibrator. https://doi.org/10.1093/mnrasl%2Fslae106

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