CRIRES+: a cross-dispersed high-resolution infrared spectrograph for the ESO VLT

Follert, Roman; Dorn, Reinhold J.; Oliva, E.; Lizon, Jean Louis; Hatzes, A. P.; Piskunov, Nikolai; Reiners, A.; Seemann, U.; Stempels, Eric; Heiter, U.; Marquart, Thomas; Lockhart, M.; Anglada‐Escudé, G.; Löwinger, Tom; Baade, D.; Grunhut, J.; Bristow, Paul; Klein, Barbara; Jung, Yves; Ives, Derek; Kerber, F.; Pozna, Eszter; Paufique, J.; Kaeufl, H. U.; Origlia, L.; Valenti, E.; Gojak, D.; Hilker, M.; Pasquini, L.; Smette, A.; Smoker, J. V.

doi:10.1117/12.2054197

Cited by 48 publications

(11 citation statements)

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“…Additionally, confidences may improve with wider wavelength coverage, as cross-correlation will involve more spectral features. The upcoming CRIRES+ (Follert et al 2014) will provide dramatic improvements upon the existing instrument, including 10× the wavelength coverage. As discussed in Brogi et al (2017), high-resolution spectroscopy may also be combined with low-resolution observations to better constrain molecular detections and abundances.…”

Section: Summary and Discussionmentioning

confidence: 99%

On the robustness of analysis techniques for molecular detections using high-resolution exoplanet spectroscopy

Cabot

Madhusudhan

Hawker

et al. 2018

Monthly Notices of the Royal Astronomical Society

115

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High-resolution doppler spectroscopy provides a powerful means for chemical detections in exoplanetary atmospheres. This approach involves monitoring hundreds of molecular lines in the planetary spectrum doppler shifted by the orbital motion of the planet. The molecules are detected by cross-correlating the observed spectrum of the system with a model planetary spectrum. The method has led to molecular detections of H 2 O, CO, and TiO in hot Jupiters using large ground-based telescopes. Critical to this method, however, is the accurate removal of the stellar and telluric features from the observed spectrum, also known as detrending. Previous molecular detections have relied on specific choices of detrending methods and parameters. However, the robustness of molecular detections across the different choices has not been investigated in detail. We conduct a systematic investigation of the effect of detrending algorithms, parameters, and optimizations on chemical detections using high-resolution spectroscopy. As a case study, we consider the hot Jupiter HD 189733 b. Using multiple methods, we confirm high-significance detections of H 2 O (4.8σ) and CO (4.7σ). Additionally, we report evidence for HCN at high significance (5.0σ). On the other hand, our results highlight the need for improved metrics and extended observations for robust confirmations of such detections. In particular, we show that detection significances of 4σ can be obtained by optimizing detrending at incorrect locations in the planetary velocity space; such false positives can occur in nearly 30% of cases. We discuss approaches to help distinguish molecular detections from spurious noise.

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Section: Summary and Discussionmentioning

confidence: 99%

On the robustness of analysis techniques for molecular detections using high-resolution exoplanet spectroscopy

Cabot

Madhusudhan

Hawker

et al. 2018

Monthly Notices of the Royal Astronomical Society

115

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“…Firstly, the current TESS mission will provide many exoplanet candidates orbiting bright enough stars for characterisation with this method. Secondly, a wealth of high-resolution observations is expected with the commissioning of CRIRES+ at the VLT (Follert et al 2014) as well as other high throughput instruments such as CARMENES (Quirrenbach et al 2014). The use of smaller telescopes with high throughput spectrographs such as GI-ANO has been shown to prove fruitful in HRS exoplanet spectroscopy (Brogi et al 2018;Guilluy et al 2019).…”

Section: High-resolution Parametersmentioning

confidence: 99%

HyDRA-H: Simultaneous Hybrid Retrieval of Exoplanetary Emission Spectra

Gandhi

Madhusudhan

Hawker

et al. 2019

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High-resolution Doppler spectroscopy has been used to detect several chemical species in exoplanetary atmospheres. Such detections have traditionally relied on cross correlation of observed spectra against spectral model templates, an approach that is successful for detecting chemical species but not optimised for constraining abundances. Recent work has explored ways to perform atmospheric retrievals on high-resolution spectra (HRS) and combine them with retrievals routinely performed for low-resolution spectra (LRS) by developing a mapping from the cross correlation function to a likelihood metric. We build upon previous studies and report HyDRA-H, a hybrid retrieval code for simultaneous analysis of low-and high-resolution thermal emission spectra of exoplanets in a fully Bayesian approach. We demonstrate HyDRA-H on the hot Jupiter HD 209458b as a case study. We validate our HRS retrieval capability by confirming previous results and report a simultaneous hybrid retrieval using both HRS and LRS data. The LRS data span the HST WFC3 (1.1-1.7 µm) and Spitzer photometry (IRAC 3.6-8µm) bands, while the HRS data were obtained with CRIRES on VLT at 2.3 µm. The constraints on the composition and temperature profiles for the hybrid retrieval are more stringent than retrievals with either LRS or HRS datasets individually. We retrieve abundances of log(H 2 O) = −4.11 +0.91 −0.30 and log(CO) = −2.16 +0.99 −0.47 , and C/O = 0.99 +0.01 −0.02 , consistent with previous works. We constrain the photospheric temperature to be 1498 +216 −57 K, consistent with the equilibrium temperature. Our results demonstrate the significant advantages of hybrid retrievals by combining strengths of both HRS and LRS observations which probe complementary aspects of exoplanetary atmospheres.

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“…The NIR high resolution instrument SPIRou (Artigau et al 2014), which has an even larger simultaneous wavelength coverage with a resolving power of R ∼ 73,000, is currently in operation and should also produce detections at a S/N competitive with or superior to what was possible with CRIRES. And finally, CRIRES+ (Follert et al 2014), which is expected to receive its first light in early 2020, will succeed the highly successful CRIRES instrument to provide improved stability and simultaneous NIR coverage by a factor of ten from its predecessor.…”

Section: Discussionmentioning

confidence: 99%

A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band

Webb

Brogi

Gandhi

et al. 2020

Monthly Notices of the Royal Astronomical Society

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High resolution spectroscopy (R 20, 000) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES (R = 100, 000) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 µm. We observe a weak (3.0 σ, or S/N = 4.8) spectral signature of H 2 O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K -band, we measure a detection significance of 8.4 σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H 2 O being the only major sources of opacity in this wavelength range. As the two sets of data were taken three years apart, this points to the absence of strong radial-velocity anomalies due, e.g., to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of K P = (145.2 ± 2.0) km s −1 (1 σ) and improve the error bars on this parameter by ∼70%. However, we only marginally tighten constraints on orbital inclination (66.2 +3.7 −3.1 degrees) and planet mass (0.963 +0.036 −0.031 Jupiter masses), due to the dominant uncertainties of stellar mass and semi-major axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterisation via high resolution spectroscopy.

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CRIRES+: a cross-dispersed high-resolution infrared spectrograph for the ESO VLT

Cited by 48 publications

References 1 publication

On the robustness of analysis techniques for molecular detections using high-resolution exoplanet spectroscopy

On the robustness of analysis techniques for molecular detections using high-resolution exoplanet spectroscopy

HyDRA-H: Simultaneous Hybrid Retrieval of Exoplanetary Emission Spectra

A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band

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