Prospects for near-infrared characterisation of hot Jupiters with VSI

TL;DR

This study assesses the potential of the VSI instrument at VLT to obtain near-infrared spectra of hot Jupiters, demonstrating feasible low-resolution spectral retrievals that could inform on planetary atmospheres and compositions.

Contribution

It presents a simulation-based feasibility analysis of using VSI for near-infrared characterization of hot Jupiters, highlighting instrumental stability and observational strategies.

Findings

Low-resolution spectra can be retrieved for several hot Jupiters within 10 hours.

Spectroscopic data can constrain planetary temperature, albedo, and atmospheric composition.

Instrumental stability is crucial for accurate spectral reconstruction.

Abstract

In this paper, we study the feasibility of obtaining near-infrared spectra of bright extrasolar planets with the 2nd generation VLTI Spectro-Imager instrument (VSI), which has the required angular resolution to resolve nearby hot Extrasolar Giant Planets (EGPs) from their host stars. Taking into account fundamental noises, we simulate closure phase measurements of several extrasolar systems using four 8-m telescopes at the VLT and a low spectral resolution (R = 100). Synthetic planetary spectra from T. Barman are used as an input. Standard chi2-fitting methods are then used to reconstruct planetary spectra from the simulated data. These simulations show that low-resolution spectra in the H and K bands can be retrieved with a good fidelity for half a dozen targets in a reasonable observing time (about 10 hours, spread over a few nights). Such observations would strongly constrain the planetary temperature and albedo, the energy redistribution mechanisms, as well as the chemical composition of their atmospheres. Systematic errors, not included in our simulations, could be a serious limitation to these performance estimations. The use of integrated optics is however expected to provide the required instrumental stability (around 10^-4 on the closure phase) to enable the first thorough characterisation of extrasolar planetary emission spectra in the near-infrared.