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White Dwarfs Accreting Planetary Material Determined from X-ray Observations

Presentation #302.05 in the session Planets Around White Dwarfs.

Published onApr 03, 2024
White Dwarfs Accreting Planetary Material Determined from X-ray Observations

Over a quarter of white dwarf stars show the presence of metals in their atmospheres. This is interpreted as a signature of accretion of debris from asteroids, comets, and planets which have been scattered towards the central stellar remnant. We have recently made the first direct detection of planetary material accreting onto a white dwarf using X-ray observations. This discovery confirms G29—38 - the prototype of all metal-polluted white dwarfs with detected debris disks – as a significant source of soft X-rays. Our detection relied on a 106 ks exposure with the Chandra X-ray Observatory and provides the first direct evidence of ongoing accretion of planetary material onto a white dwarf. From the measured low-energy X-ray spectrum, we provide the first independent constraint on the accretion rate at such a system, finding an instantaneous accretion rate consistent with modelling of observed photospheric abundances. I will present this recent discovery, together with additional joint modelling of X-ray and UV observations, and its implications for the study of evolved planetary systems, including the accretion rates and bulk elemental compositions. I will also present recent results from on ongoing survey of isolated white dwarfs with X-ray emission.

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