| 1. |
- 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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| 2. |
- Wehrhahn, Ansgar, 1991-
(författare)
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High Resolution Transmission Spectroscopy of Exoplanets
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A large number of exoplanets has been observed in the last three decades, but still for most of them we know comparatively little about the atmospheres of these distant planets. This is of particular interest as there exist types of planets that don't have an analogy in our own solar system, like hot Jupiters or super Earths. Studying these is instrumental in understanding planet and solar system formation. However just as planets are much smaller than their host stars, so is their signal in the observations. We therefore require high-precision measurements and analysis methods to study them. In this thesis I focus on ground-based high-resolution spectroscopy, as this allows us to use the information encoded in individual absorption lines of the spectrum. I developed tools for the entire process from the initial data reduction, over the analysis of the host star, to the final planet atmosphere characterization.The first tool I developed is PyReduce. It performs data reduction on raw observation images of high-resolution spectrographs by correcting for noise and bias in the data. Of special interest is the new extraction algorithm, which properly accounts for the optical distortions in the spectrograph, and thus improves the quality of the recovered spectrum.The second tool is PySME, which determines the fundamental parameters of the host stars, by modelling the stellar atmosphere and comparing it to the observed spectrum. Accurate stellar parameters help us understand the star-planet system, especially regarding the stellar irradiation on the planet which is important for the temperature. Finally I created ChEATS to determine the chemical components of the planet atmosphere using the cross-correlation method. This method combines all observed spectral lines to detect the faint planet signal in the data. We show that these tools provide excellent analyses in the papers presented here. Additionally PyReduce and PySME are in active use by scientists all over the world. Finally we present an analysis of WASP-107 b, in which we detect H2O and CO in the planet atmosphere.
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| 3. |
- Wehrhahn, Ansgar, et al.
(författare)
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PySME : Spectroscopy Made Easier
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 671
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Tidskriftsartikel (refereegranskat)abstract
- Context: The characterization of exoplanets requires the reliable determination of the fundamental parameters of their host stars. Spectral fitting plays an important role in this process. For the majority of stellar parameters, matching synthetic spectra to the observations provides a robust and unique solution for the fundamental parameters, such as effective temperature, surface gravity, abundances, radial and rotational velocities, among others.Aims: Here, we present a new software package for fitting high-resolution stellar spectra that is easy to use, available for common platforms, and free from commercial licenses. We call it PySME. It is based on the proven Spectroscopy Made Easy package, later referred to as IDL SME or "original" SME.Methods: The IDL (Interactive Data Language) part of the original SME code has been rewritten in Python, but we kept the efficient C++ and FORTRAN code responsible for molecular-ionization equilibrium, opacities, and spectral synthesis. In the process we updated some components of the optimization procedure to offer more flexibility and better analysis of the convergence. The result is a more modern package with the same functionality as the original SME.Results: We applied PySME to a few stars of different spectral types and compared the derived fundamental parameters with the results from IDL SME and other techniques. We show that PySME works at least as well as the original SME.
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