| 1. |
- Glauser, A. M., et al.
(författare)
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Characterizing exoplanets in the visible and infrared: A spectrometer concept for the EChO space mission
- 2013
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Ingår i: Journal of Astronomical Instrumentation. - 2251-1725 .- 2251-1717. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Transit-spectroscopy of exoplanets is one of the key observational techniques used to characterize extrasolar planets and their atmospheres. The observational challenges of these measurements require dedicated instrumentation and only the space environment allows undisturbed access to earth-like atmospheric features such as water or carbon dioxide. Therefore, several exoplanet-specific space missions are currently being studied. One of them is EChO, the Exoplanet Characterization Observatory, which is part of ESA's Cosmic Vision 2015-2025 program, and which is one of four candidates for the M3 launch slot in 2024. In this paper we present the results of our assessment study of the EChO spectrometer, the only science instrument onboard this spacecraft. The instrument is a multi-channel all-reflective dispersive spectrometer, covering the wavelength range from 400 nm to 16μm simultaneously with a moderately low spectral resolution. We illustrate how the key technical challenge of the EChO mission - the high photometric stability - influences the choice of spectrometer concept and fundamentally drives the instrument design. First performance evaluations underline the suitability of the elaborated design solution for the needs of the EChO mission.
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| 2. |
- Dorn, R. J., et al.
(författare)
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CRIRES+ on sky at the ESO Very Large Telescope : Observing the Universe at infrared wavelengths and high spectral resolution
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 671
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Tidskriftsartikel (refereegranskat)abstract
- The CRyogenic InfraRed Echelle Spectrograph (CRIRES) Upgrade project CRIRES+ extended the capabilities of CRIRES. It transformed this VLT instrument into a cross-dispersed spectrograph to increase the wavelength range that is covered simultaneously by up to a factor of ten. In addition, a new detector focal plane array of three Hawaii 2RG detectors with a 5.3 mu m cutoff wavelength replaced the existing detectors. Amongst many other improvements, a new spectropolarimetric unit was added and the calibration system has been enhanced. The instrument was installed at the VLT on Unit Telescope 3 at the beginning of 2020 and successfully commissioned and verified for science operations during 2021, partly remotely from Europe due to the COVID-19 pandemic. The instrument was subsequently offered to the community from October 2021 onwards. This article describes the performance and capabilities of the upgraded instrument and presents on sky results.
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| 3. |
- Follert, R., et al.
(författare)
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CRIRES plus : a cross-dispersed high-resolution infrared spectrograph for the ESO VLT
- 2014
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Ingår i: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V. - : SPIE. - 9780819496157
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Konferensbidrag (refereegranskat)abstract
- High-resolution infrared spectroscopy plays an important role in astrophysics from the search for exoplanets to cosmology. Yet, many existing infrared spectrographs are limited by a rather small simultaneous wavelength coverage. The AO assisted CRIRES instrument, installed at the ESO VLT on Paranal, is one of the few IR (0.92-5.2 mu m) high-resolution spectrographs in operation since 2006. However it has a limitation that hampers its efficient use: the wavelength range covered in a single exposure is limited to similar to 15 nanometers. The CRIRES Upgrade project (CRIRES+) will transform CRIRES into a cross-dispersed spectrograph and will also add new capabilities. By introducing cross-dispersion elements the simultaneously covered wavelength range will be increased by at least a factor of 10 with respect to the present configuration, while the operational wavelength range will be preserved. For advanced wavelength calibration, new custom made absorption gas cells and etalons will be added. A spectro-polarimetric unit will allow one for the first time to record circularly polarized spectra at the highest spectral resolution. This will be all supported by a new data reduction software which will allow the community to take full advantage of the new capabilities of CRIRES+.
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| 4. |
- Lebzelter, T., et al.
(författare)
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CRIRES-POP A library of high resolution spectra in the near-infrared
- 2012
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 539
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Tidskriftsartikel (refereegranskat)abstract
- Context. New instrumental capabilities and the wealth of astrophysical information extractable from the near-infrared wavelength region have led to a growing interest in the field of high resolution spectroscopy at 1-5 mu m. Aims. We aim to provide a library of observed high-resolution and high signal-to-noise-ratio near-infrared spectra of stars of various types throughout the Hertzsprung-Russell diagram. This is needed for the exploration of spectral features in this wavelength range and for comparison of reference targets with observations and models. Methods. High quality spectra were obtained using the CRIRES near-infrared spectrograph at ESO's VLT covering the range from 0.97 mu m to 5.3 mu m at high spectral resolution. Accurate wavelength calibration and correction for telluric lines were performed by fitting synthetic transmission spectra for the Earth's atmosphere to each spectrum individually. Results. We describe the observational strategy and the current status and content of the library which includes 13 objects. The first examples of finally reduced spectra are presented. This publication will serve as a reference paper to introduce the library to the community and explore the extensive amount of material.
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| 5. |
- Nicholls, Christine P, et al.
(författare)
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CRIRES-POP : a library of high resolution spectra in the near-infrared II. Data reduction and the spectrum of the K giant 10 Leonis
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 598
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Tidskriftsartikel (refereegranskat)abstract
- Context. High resolution stellar spectral atlases are valuable resources to astronomy. They are rare in the 1 − 5 μm region for historical reasons, but once available, high resolution atlases in this part of the spectrum will aid the study of a wide range of astrophysical phenomena. Aims. The aim of the CRIRES-POP project is to produce a high resolution near-infrared spectral library of stars across the H-R diagram. The aim of this paper is to present the fully reduced spectrum of the K giant 10 Leo that will form the basis of the first atlas within the CRIRES-POP library, to provide a full description of the data reduction processes involved, and to provide an update on the CRIRES-POP project. Methods. All CRIRES-POP targets were observed with almost 200 different observational settings of CRIRES on the ESO Very Large Telescope, resulting in a basically complete coverage of its spectral range as accessible from the ground. We reduced the spectra of 10 Leo with the CRIRES pipeline, corrected the wavelength solution and removed telluric absorption with Molecfit, then resampled the spectra to a common wavelength scale, shifted them to rest wavelengths, flux normalised, and median combined them into one final data product. Results. We present the fully reduced, high resolution, near-infrared spectrum of 10 Leo. This is also the first complete spectrum from the CRIRES instrument. The spectrum is available online. Conclusions. The first CRIRES-POP spectrum has exceeded our quality expectations and will form the centre of a state-of-the-art stellar atlas. This first CRIRES-POP atlas will soon be available, and further atlases will follow. All CRIRES-POP data products will be freely and publicly available online.
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| 6. |
- Oliva, E., et al.
(författare)
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Concept and optical design of the cross-disperser module for CRIRES
- 2014
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Ingår i: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V. - : SPIE. - 9780819496157
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Konferensbidrag (refereegranskat)abstract
- CRIRES, the ESO high resolution infrared spectrometer, is a unique instrument which allows astronomers to access a parameter space which up to now was largely uncharted. In its current setup, it consists of a single-order spectrograph providing long-slit, single-order spectroscopy with resolving power up to R=100,000 over a quite narrow spectral range. This has resulted in sub-optimal efficiency and use of telescope time for all the scientific programs requiring broad spectral coverage of compact objects (e.g. chemical abundances of stars and intergalactic medium, search and characterization of extra-solar planets). To overcome these limitations, a consortium was set-up for upgrading CRIRES to a cross-dispersed spectrometer, called CRIRES+. This paper presents the updated optical design of the cross-dispersion module for CRIRES+. This new module can be mounted in place of the current pre-disperser unit. The new system yields a factor of >10 increase in simultaneous spectral coverage and maintains a quite long slit (10"), ideal for observations of extended sources and for precise sky-background subtraction.
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| 7. |
- Seemann, U., et al.
(författare)
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Wavelength calibration from 1-5 mu m for the CRIRES plus high-resolution spectrograph at the VLT
- 2014
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Ingår i: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V. - : SPIE. - 9780819496157
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Konferensbidrag (refereegranskat)abstract
- CRIRES at the VLT is one of the few adaptive optics enabled instruments that offer a resolving power of 10 5 from 1 - 5 mu m. An instrument upgrade (CRIRES+) is proposed to implement cross-dispersion capabilities, spectro-polarimetry modes, a new detector mosaic, and a new gas absorption cell. CRIRES+ will boost the simultaneous wavelength coverage of the current instrument (similar to lambda/70 in a single-order) by a factor of greater than or similar to 10 in the cross-dispersed configuration, while still retaining a 10 arcsec slit suitable for long-slit spectroscopy. CRIRES+ dramatically enhances the instrument's observing efficiency, and opens new scientific opportunities. These include high-precision radial-velocity studies on the 3m/s level to characterize extra-solar planets and their athmospheres, which demand for specialized, highly accurate wavelength calibration techniques. In this paper, we present a newly developed absorption gas-cell to enable high-precision wavelength calibration for CRIRES+. We also discuss the strategies and developments to cover the full operational spectral range (1-5 mu m), employing hollow-cathode emission lamps, Fabry-Perot etalons, and absorption gas-cells.
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| 8. |
- Hahlin, Axel, et al.
(författare)
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Determination of small-scale magnetic fields on Sun-like stars in the near-infrared using CRIRES
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 675
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Tidskriftsartikel (refereegranskat)abstract
- Aims: We aim to characterise the small-scale magnetic fields of a sample of 16 Sun-like stars and investigate the capabilities of the newly upgraded near-infrared (NIR) instrument CRIRES+ at the Very Large Telescope in the context of small-scale magnetic field studies. Our targets also had their magnetic fields studied with optical spectra, which allowed us to compare magnetic field properties at different spatial scales on the stellar surface and to contrast small-scale magnetic field measurements at different wavelengths.Methods: We analysed the Zeeman broadening signature for six magnetically sensitive and insensitive Fe I lines in the H-band to measure small-scale magnetic fields on the stellar surfaces of our sample. We used polarised radiative transfer modelling and non-local thermodynamic equilibrium departure coefficients in combination with Markov chain Monte Carlo sampling to determine magnetic field characteristics and non-magnetic stellar parameters. We used two different approaches to describe the small-scale magnetic fields. The first is a two-component model with a single magnetic region and a free magnetic field strength. The second model contains multiple magnetic components with fixed magnetic field strengths.Results: We found average magnetic field strengths ranging from & SIM;0.4 kG down to < 0.1 kG. The results align closely with other results from high-resolution NIR spectrographs, such as SPIRou. It appears that the typical magnetic field strength in the magnetic region is slightly stronger than 1.3 kG, and for most stars in our sample, this strength is between 1 and 2 kG. We also found that the small-scale fields correlate with the large-scale fields and that the small-scale fields are at least ten times stronger than the large-scale fields inferred with Zeeman Doppler imaging. The two- and multi-component models produce systematically different results, as the strong fields from the multi-component model increase the obtained mean magnetic field strength. When comparing our results with the optical measurements of small-scale fields, we found a systematic offset two to three times stronger than fields in the optical results. This discrepancy cannot be explained by uncertainties in stellar parameters. Care should therefore be taken when comparing results obtained at different wavelengths until a clear cause can be established.
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| 9. |
- Krueger, Martin W., et al.
(författare)
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In-silico modeling of atrial repolarization in normal and atrial fibrillation remodeled state
- 2013
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Ingår i: Medical & Biological Engineering & Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 51:10, s. 1105-1119
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Tidskriftsartikel (refereegranskat)abstract
- Atrial fibrillation (AF) is the most common cardiac arrhythmia, and the total number of AF patients is constantly increasing. The mechanisms leading to and sustaining AF are not completely understood yet. Heterogeneities in atrial electrophysiology seem to play an important role in this context. Although some heterogeneities have been used in in-silico human atrial modeling studies, they have not been thoroughly investigated. In this study, the original electrophysiological (EP) models of Courtemanche et al., Nygren et al. and Maleckar et al. were adjusted to reproduce action potentials in 13 atrial regions. The parameter sets were validated against experimental action potential duration data and ECG data from patients with AV block. The use of the heterogeneous EP model led to a more synchronized repolarization sequence in a variety of 3D atrial anatomical models. Combination of the heterogeneous EP model with a model of persistent AF-remodeled electrophysiology led to a drastic change in cell electrophysiology. Simulated Ta-waves were significantly shorter under the remodeling. The heterogeneities in cell electrophysiology explain the previously observed Ta-wave effects. The results mark an important step toward the reliable simulation of the atrial repolarization sequence, give a deeper understanding of the mechanism of atrial repolarization and enable further clinical investigations.
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| 10. |
- Lesjak, F., et al.
(författare)
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Retrieval of the dayside atmosphere of WASP-43b with CRIRES
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 678
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Tidskriftsartikel (refereegranskat)abstract
- Accurately estimating the C/O ratio of hot Jupiter atmospheres is a promising pathway towards understanding planet formation and migration, as well as the formation of clouds and the overall atmospheric composition. The atmosphere of the hot Jupiter WASP-43b has been extensively analysed using low-resolution observations with HST and Spitzer, but these previous observations did not cover the K band, which hosts prominent spectral features of major carbon-bearing species such as CO and CH4. As a result, the ability to establish precise constraints on the C/O ratio was limited. Moreover, the planet has not been studied at high spectral resolution, which can provide insights into the atmospheric dynamics. In this study, we present the first high-resolution dayside spectra of WASP-43b with the new CRIRES+ spectrograph. By observing the planet in the K band, we successfully detected the presence of CO and provide evidence for the existence of H2O using the cross-correlation method. This discovery represents the first direct detection of CO in the atmosphere of WASP-43b. Furthermore, we retrieved the temperature-pressure profile, abundances of CO and H2O, and a super-solar C/O ratio of 0.78 by applying a Bayesian retrieval framework to the data. Our findings also shed light on the atmospheric characteristics of WASP-43b. We found no evidence for a cloud deck on the dayside, and recovered a line broadening indicative of an equatorial super-rotation corresponding to a jet with a wind speed of similar to 5kms(-1), matching the results of previous forward models and low-resolution atmospheric retrievals for this planet.
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| 11. |
- Shulyak, D., et al.
(författare)
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Exploring the magnetic field complexity in M dwarfs at the boundary to full convection
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 563, s. A35-
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Tidskriftsartikel (refereegranskat)abstract
- Context. Magnetic fields play a pivotal role in the formation and evolution of low-mass stars, but the dynamo mechanisms generating these fields are poorly understood. Measuring cool star magnetism is a complicated task because of the complexity of cool star spectra and the subtle signatures of magnetic fields. Aims. Based on detailed spectral synthesis, we carry out quantitative measurements of the strength and complexity of surface magnetic fields in the four well-known M dwarfs GJ 388, GJ 729, GJ 285, and GJ 406 that populate the mass regime around the boundary between partially and fully convective stars. Very high-resolution (R = 100 000), high signal-to-noise (up to 400), near-infrared Stokes I spectra were obtained with CRIRES at ESO's Very Large Telescope covering regions of the FeH Wing-Ford transitions at 1 mu m and Na I lines at 2.2 mu m. Methods. A modified version of the Molecular Zeeman Library (MZL) was used to compute Lande g-factors for FeH lines. We determined the distribution of magnetic fields by magnetic spectral synthesis performed with the SYNMAST code. We tested two different magnetic geometries to probe the influence of field orientation effects. Results. Our analysis confirms that FeH lines are excellent indicators of surface magnetic fields in low-mass stars of type M, particularly in comparison to profiles of Na I lines that are heavily affected by water lines and that suffer problems with continuum normalization. The field distributions in all four stars are characterized by three distinct groups of field components, and the data are consistent neither with a smooth distribution of different field strengths nor with one average field strength covering the full star. We find evidence of a subtle difference in the field distribution of GJ 285 compared to the other three targets. GJ 285 also has the highest average field of 3.5 kG and the strongest maximum field component of 7-7.5 kG. The maximum local field strengths in our sample seem to be correlated with rotation rate. While the average field strength is saturated, the maximum local field strengths in our sample show no evidence of saturation. Conclusions. We find no difference between the field distributions of partially and fully convective stars. The one star with evidence of field distribution different from the other three is the most active star (i.e. with X-ray luminosity and mean surface magnetic field) rotating relatively fast. A possible explanation is that rotation determines the distribution of surface magnetic fields, and that local field strengths grow with rotation even in stars in which the average field is already saturated.
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| 12. |
- Yan, F., et al.
(författare)
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CRIRES+ detection of CO emissions lines and temperature inversions on the dayside of WASP-18b and WASP-76b
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 672
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Tidskriftsartikel (refereegranskat)abstract
- The dayside atmospheres of ultra-hot Jupiters (UHJs) are predicted to possess temperature inversion layers with extremely high temperatures at high altitudes. We observed the dayside thermal emission spectra of WASP-18b and WASP-76b with the new CRIRES+ high-resolution spectrograph at near-infrared wavelengths. Using the cross-correlation technique, we detected strong CO emission lines in both planets, which confirms the existence of temperature inversions on their dayside hemispheres. The two planets are the first UHJs orbiting F-type stars with CO emission lines detected; previous detections were mostly for UHJs orbiting A-type stars. Evidence of weak H2O emission signals is also found for both planets. We further applied forward-model retrievals on the detected CO lines and retrieved the temperature-pressure profiles along with the CO volume mixing ratios. The retrieved logarithmic CO mixing ratio of WASP-18b (-2.2(-1.5)(+1.4)) is slightly higher than the value predicted by the self-consistent model assuming solar abundance. For WASP-76b, the retrieved CO mixing ratio (-3.6(-1.6)(+1.8)) is broadly consistent with the value of solar abundance. In addition, we included the equatorial rotation velocity (upsilon(eq)) in the retrieval when analyzing the line profile broadening. The obtained upsilon(eq) is 7.0 +/- 2.9 km s(-1) for WASP-18b and 5.2(-3.0)(+2.5) km s(-1) for WASP-76b, which are consistent with the tidally locked rotational velocities.
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