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Thermal Emission from the First Giant Planet Transiting a White Dwarf

Presentation #302.02 in the session Planets Around White Dwarfs.

Published onApr 03, 2024
Thermal Emission from the First Giant Planet Transiting a White Dwarf

Most known exoplanets orbit stars which will eventually evolve into white dwarfs, but little is known about the fates of these systems after their hosts leave the main sequence. The first transiting planet candidate found orbiting a white dwarf, WD 1856 b, could therefore play an important role in our understanding of post-main-sequence planetary evolution. However, much is still unknown about its origins, including how it reached its current orbit. The best way to distinguish between possible formation scenarios is by constraining WD 1856 b’s mass, as a lower (~1 Jupiter mass) mass would likely indicate the planet had migrated in at high eccentricity, while a larger (10-15 Jupiter masses) mass leaves common envelope evolution as a viable explanation. To constrain WD 1856 b’s mass, we search for its thermal emission with JWST/NIRSPEC spectroscopy. Because massive planets cool more slowly than low-mass planets over time, WD 1856 b’s infrared brightness, combined with our rough knowledge of the planet’s age, yields its mass. The thermal emission also provides insight into the properties of the planet’s atmosphere. We present results and discuss the implications for the formation of WD 1856 b and the fate of giant planets in post-main-sequence systems.

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