Planetary Engulfment Prognosis within the ρ CrB System

Abstract

Exoplanets have been detected around stars at various stages of their lives, ranging from young stars emerging from formation to the latter stages of evolution, including white dwarfs and neutron stars. Post-main-sequence stellar evolution can result in dramatic, and occasionally traumatic, alterations to the planetary system architecture, such as tidal disruption of planets and engulfment by the host star. The ρ CrB system is a particularly interesting case of advanced main-sequence evolution, due to the relative late age and brightness of the host star, its similarity to solar properties, and the harboring of four known planets. Here, we use stellar evolution models to estimate the expected trajectory of the stellar properties of ρ CrB, especially over the coming 1.0–1.5 billion yr as it evolves off the main sequence. We show that the inner three planets (e, b, and c) are engulfed during the red giant phase and asymptotic giant branch, likely destroying those planets via either evaporation or tidal disruption at the fluid-body Roche limit. The outer planet, planet d, is briefly engulfed by the star several times toward the end of the asymptotic giant branch, but the stellar mass loss and subsequent changing planetary orbit may allow the survival of the planet into the white dwarf phase of the stellar evolution. We discuss the implications of this outcome for similar systems and describe the consequences for planets that may lie within the habitable zone of the system.

The TESS-Keck Survey: * Science Goals and Target Selection

“…9 https://github.com/danxhuber/isoclassify We used the values of T eff and [Fe/H] (discussed in the previous section) as spectroscopic inputs, along with parallaxes from Gaia Data Release 3 (DR3; Gaia Collaboration et al 2021Collaboration et al , 2023. In order to further constrain the results and fit for extinction directly, we also included Johnson BV photometry, JHK s from 2MASS (Skrutskie et al 2006) and GB p R p from Gaia (Gaia Collaboration et al 2021, 2023. For Gaia DR3 photometry, we adopted a systematic noise floor of 0.01 mag.…”

“…The existence of exoplanets orbiting stars in advanced evolutionary stages such as helium-core burning red giants (Hon et al 2023), white dwarfs (Vanderburg et al 2020) and pulsars (Wolszczan & Frail 1992) suggests that planets are able to withstand extreme environments present at the latest stages of stellar evolution. Most known exoplanets will face a similar fate as their host stars eventually evolve off the mainsequence (Kane 2023), yet the planet populations around post-main-sequence stars remain poorly understood.…”