Constraining the Bulk Composition of Disintegrating Exoplanets Using Combined Transmission Spectra from JWST and SPICA

TL;DR

This study demonstrates that combining JWST and SPICA infrared transmission spectra can effectively constrain the mineral composition of dust tails around disintegrating exoplanets, revealing their surface mineralogy.

Contribution

It introduces a method to use combined JWST and SPICA spectra to diagnose dust tail composition, enhancing the understanding of disintegrating exoplanets' surfaces.

Findings

JWST can detect silicate and carbide features with high confidence in suitable targets.

SPICA can distinguish between Fe- and Mg-rich crystalline silicates in the dust tails.

Combined spectra improve constraints on planetary surface mineralogy.

Abstract

Disintegrating planets are ultra-short-period exoplanets that appear to have a comet-like dust tail. They are commonly interpreted as low-mass planets whose solid surface is evaporating and whose tail is made of recondensing minerals. Transmission spectroscopy of the dust tails could thus allow us to directly probe the elementary compositions of the planets. Previous work already investigated the feasibility of such observations using the JWST mid-infrared instrument. In this study, we explore if one can obtain a strong constrain on the tail composition by adding spectroscopy at longer wavelengths using SPICA mid-infrared instrument. We use a simple model for the spatial distribution of the dust tails and produce their synthetic transmission spectra assuming various dust compositions. We find that combined infrared spectra from JWST and SPICA will allow us to diagnose various components of the dust tails. JWST will be able to detect silicate and carbide absorption features with a feature-to-noise ratio of $\gtrsim$ 3 in the tail transmission spectrum of a disintegrating planet located within 100 pc from the Earth with a transit depth deeper than 0.5%. SPICA can distinguish between Fe- and Mg-bearing crystalline silicates for planets at $\lesssim$ 100 pc with a transit depth of $\gtrsim$ 2%. Transit searches with current and future space telescopes (e.g., $TESS$ and PLATO) will provide ideal targets for such spectroscopic observations.