Detectability of Exoplanet Periastron Passage in the Infra-Red

TL;DR

This paper explores the thermal detectability of long-period eccentric exoplanets during periastron in the infrared, assessing their properties and identifying optimal targets for follow-up observations with space telescopes.

Contribution

It introduces a method to evaluate the thermal signatures of eccentric exoplanets during periastron and recommends promising targets for infrared follow-up studies.

Findings

Certain eccentric exoplanets exhibit detectable IR flux during periastron

Thermal properties depend on orbital eccentricity and heat redistribution efficiency

Specific known exoplanets are identified as prime candidates for IR observation

Abstract

Characterization of exoplanets has matured in recent years, particularly through studies of exoplanetary atmospheres of transiting planets at infra-red wavelenegths. The primary source for such observations has been the Spitzer Space Telescope but these studies are anticipated to continue with the James Webb Space Telescope (JWST). A relatively unexplored region of exoplanet parameter space is the thermal detection of long-period eccentric planets during periastron passage. Here we describe the thermal properties and albedos of long-period giant planets along with the eccentricities of those orbits which allow them to remain within the habitable zone. We further apply these results to the known exoplanets by calculating temperatures and flux ratios for the IRAC passbands occupied by warm Spitzer, considering both low and high thermal redistribution efficiencies from the perspective of an observer. We conclude with recommendations on which targets are best suited for follow-up observations.