High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts

Ridden-Harper, Andrew; Mooij, Ernst de; Jayawardhana, Ray; Gibson, Neale P.; Karjalainen, R.; Karjalainen, Marie

doi:10.3847/1538-3881/acc654

Cited by 5 publications

(1 citation statement)

References 67 publications

(152 reference statements)

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“…Furthermore, differences between instruments could be taken advantage of in the case that observers explore the possibility of stacking multiple observations from multiple instruments, as done by e.g. Ridden-Harper et al (2023).…”

Section: Differences Between Instrumentsmentioning

confidence: 99%

Optimising spectroscopic observations of transiting exoplanets

Boldt-Christmas,

Lesjak,

Wehrhahn

et al. 2024

A&A

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When observing the atmospheres of transiting exoplanets using high-resolution spectroscopy, the aim is to detect well-resolved spectral features with high signal-to-noise ratios (S/Ns), as is possible today with modern spectrographs. However, obtaining such high-quality observations comes with a trade-off: a lower cadence of fewer, longer exposures across the transit collects more photons thanks to reduced overheads, enhancing the S/N of each observation, while a higher cadence of several shorter exposures minimises spectral feature smearing due to the continuously changing radial velocity of the planet. Considering that maximising S/N and minimising smearing are both beneficial to analysis, there is a need to identify the optimal compromise between the two for a given target. In this work, we aim to establish where this compromise lies for a typical exoplanet transit observation in order to benefit future data collection and subsequent interpretation. We modelled real transit events based on targets as they would be observed with VLT/ at Paranal Observatory, Chile. Creating four hypothetical scenarios, we simulated each set of transmission spectra across 100 realisations of the same transit event in order to vary the time resolution only. We removed telluric and stellar lines from these data sets using the algorithm and analysed them through cross-correlation with model templates, measuring how successfully each time resolution and case detected the planetary signal and exploring how the results vary. We demonstrate that there is a continuous change in the significance of the cross-correlation detection based on the trade-off between high and low time resolutions, and that, averaged over a large number of realisations, the function of this significance has clear maxima. The strength and location of these maxima vary depending on, for example, planet system parameters, instrumentation, and the number of removal iterations. We discuss why observers should therefore take several factors into account using a strategy akin to the `exposure triangle' employed in traditional photography where a balance must be struck by considering the full context of the observation. Our method is robust and may be employed by observers to estimate the best observational strategies for other targets.

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Section: Differences Between Instrumentsmentioning

confidence: 99%

Optimising spectroscopic observations of transiting exoplanets

Boldt-Christmas,

Lesjak,

Wehrhahn

et al. 2024

A&A

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The 2024 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

Tennyson,

Yurchenko,

Zhang

et al. 2024

Journal of Quantitative Spectroscopy and Radiative Transfer

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Detection of Fe and Ti on the dayside of the ultrahot Jupiter MASCARA-1b with CARMENES

Guo,

Yan,

Nortmann

et al. 2024

A&A

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Ultrahot Jupiters are a type of gaseous exoplanet that orbit extremely close to their host star, resulting in significantly high equilibrium temperatures. In recent years, high-resolution emission spectroscopy has been broadly employed in observing the atmospheres of ultrahot Jupiters. We used the CARMENES spectrograph to observe the high-resolution spectra of the dayside hemisphere of MASCARA-1b in both visible and near-infrared. Through cross-correlation analysis, we detected signals of Fe i and Ti i . Based on these detections, we conducted an atmospheric retrieval and discovered the presence of a strong inversion layer in the planet's atmosphere. The retrieved Ti and Fe abundances are broadly consistent with solar abundances. In particular, we obtained a relative abundance of Ti/Fe as $-1.0 0.8$ under the free retrieval and $ under the chemical equilibrium retrieval, suggesting the absence of significant titanium depletion on this planet. Furthermore, we considered the influence of planetary rotation on spectral line profiles. The resulting equatorial rotation speed was determined to be $4.4^ $, which agrees with the rotation speed induced by tidal locking.

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High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts

Cited by 5 publications

References 67 publications

Optimising spectroscopic observations of transiting exoplanets

Optimising spectroscopic observations of transiting exoplanets

The 2024 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

Detection of Fe and Ti on the dayside of the ultrahot Jupiter MASCARA-1b with CARMENES

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