Imaging & Spectroscopy

Feasibility Of High-Resolution Transmission Spectroscopy For Low-Velocity Exoplanets

By Keith Cowing
Status Report
March 29, 2024
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Feasibility Of High-Resolution Transmission Spectroscopy For Low-Velocity Exoplanets
Recovery of an NH3 signal injected with zero orbital velocity. The detection S/N across 𝐾p- 𝑉sys space is shown when an NH3 signal is injected into the spectra with no semi-amplitude radial velocity (𝐾p= 0 km s−1 ) and no barycentric velocity correction and then recovered as in Figure 2. A signal with a S/N of 4.7, unconstrained in 𝐾p, is recovered at the correct 𝑉sys .astro-ph.EP

In recent years, high-resolution transmission spectroscopy in the near-infrared has led to detections of prominent molecules in several giant exoplanets on close-in orbits.

This approach has traditionally relied on the large Doppler shifts of the planetary spectral lines induced by the high velocities of the close-in planets, which were considered necessary for separating them from the quasi-static stellar and telluric lines.

In this work we demonstrate the feasibility of high-resolution transmission spectroscopy for chemical detections in atmospheres of temperate low-mass exoplanets around M dwarfs with low radial velocity variation during transit.

We pursue this goal using model injection and recovery tests with H- and K- band high-resolution spectroscopy of the temperate sub-Neptune TOI-732 c, observed using the IGRINS spectrograph on Gemini-S. We show that planetary signals in transit may be recovered when the change in the planet’s radial velocity is very small, down to sub-pixel velocities. This is possible due to the presence of the planetary signal in only a subset of the observed spectra.

A sufficient number of out-of-transit spectra can create enough contrast between the planet signal and telluric/stellar contaminants that the planet signal does not constitute a principal component of the time-series spectra and can therefore be isolated using PCA-based detrending without relying on a significant Doppler shift. We additionally explore novel metrics for finding such signals, and investigate trends in their detectability.

Our work extends the scope of high-resolution transmission spectroscopy and creates a pathway towards the characterisation of habitable sub-Neptune worlds with ground-based facilities.

Connor Cheverall, Nikku Madhusudhan

Comments: Accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2403.18894 [astro-ph.EP] (or arXiv:2403.18894v1 [astro-ph.EP] for this version)
Submission history
From: Connor Cheverall
[v1] Wed, 27 Mar 2024 18:00:01 UTC (684 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻