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Planets in the Neptune Desert Are Hot Jupiters Gone Wrong

Presentation #301.06 in the session Formation and Demographics I.

Published onApr 03, 2024
Planets in the Neptune Desert Are Hot Jupiters Gone Wrong

A remarkable development over the past five years has been the discovery of planets deep within the Neptune desert, a region of the planetary mass-period diagram previously devoid of planets. We present multiple lines of evidence suggesting that these extreme planets are the exposed high-metallicity cores of gas giants. First, we show that Neptune desert-dwellers preferentially orbit metal-rich stars, similar to the hot Jupiters — hinting at common formation/evolution pathways. We then present the inaugural discovery from the new HARPS-N Hot Neptune Initiative: the first planet deep within the Neptune desert with a detected stellar companion. The companion probably drove high-eccentricity migration of a Jupiter-like progenitor that partially disrupted, as the planet resides at (nearly exactly) twice the tidal disruption radius for a Jupiter-sized planet. Finally, using new helium 10830 observations we demonstrate that the outflows of Neptune desert-dwellers are far weaker than expected, likely due to their high envelope metallicities. Altogether, planets in the Neptune desert are consistent with would-be hot Jupiters that underwent catastrophic envelope loss, exposing metal-rich gas at depth: they are “hot Jupiters gone wrong.”

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