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

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 $T_{\text{eff}}\approx 10000$ K, $M\approx 0.8M_{\odot }$, 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.

4 pages, 2 figures, 2 tables. Published in MNRAS Letters

References in corpus (12)

• The Gaia mission
• The James Webb Space Telescope
• A million binaries from Gaia eDR3: sample selection and validation of Gaia parallax uncertainties
• A catalogue of white dwarfs in Gaia EDR3
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• Gl86B: a white dwarf orbits an exoplanet host star
• Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-Selected Highly-Reddened AGNs
• A New Method for Finding Nearby White Dwarf Exoplanets and Detecting Biosignatures
• The McDonald Accelerating Stars Survey (MASS): White Dwarf Companions Accelerating the Sun-like Stars 12 Psc and HD 159062
• Discovery of a White Dwarf Companion to HD 159062
• A new white dwarf companion to the $\Delta \mu$ star GJ 3346
• Identification of new nearby white dwarfs using Gaia DR3

Cited by in corpus (1)

• Potential for life to exist and be detected on Earth-like planets orbiting white dwarfs