- 标题
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Atmospheric Characterization of Directly Imaged Exoplanets with <i>JWST</i> /MIRI
摘要： The Mid-Infrared instrument (MIRI) on board the James Webb Space Telescope will perform the first ever characterization of young giant exoplanets observed by direct imaging in the 5–28 μm spectral range. This wavelength range is key for both determining the bolometric luminosity of the cool known exoplanets and for accessing the strongest ammonia bands. In conjunction with shorter wavelength observations, MIRI will enable a more accurate characterization of the exoplanetary atmospheric properties. Here we consider a subsample of the currently known exoplanets detected by direct imaging, and we discuss their detectability with MIRI, either using the coronagraphic or the spectroscopic modes. By using the Exo-REM atmosphere model, we calculate the mid-infrared emission spectra of 14 exoplanets, and we simulate MIRI coronagraphic or spectroscopic observations. Specifically, we analyze four coronagraphic observational setups, which depend on (i) the target-star and reference-star offset (0, 3, 14 mas), (ii) the wavefront-error (130, 204 nm root mean square), and (iii) the telescope jitter amplitude (1.6, 7 mas). We then determine the signal-to-noise and integration time values for the coronagraphic targets whose planet-to-star contrasts range from 3.9 to 10.1 mag. We conclude that all the MIRI targets should be observable with different degrees of difficulty, which depends on the final in-flight instrument performances. Furthermore, we test for detection of ammonia in the atmosphere of the coolest targets. Finally, we present the case of HR 8799 b to discuss what MIRI observations can bring to the knowledge of a planetary atmosphere, either alone or in combination with shorter wavelength observations.
关键词： planets and satellites: fundamental parameters,planets and satellites: atmospheres,telescopes,planets and satellites: gaseous planets,instrumentation: spectrographs,instrumentation: high angular resolution
更新于2025-09-23 15:21:21
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Simulating the detection and classification of high-redshift supernovae with HARMONI on the ELT
摘要： We present detailed simulations of integral ?eld spectroscopic observations of a supernova in a host galaxy at z ～ 3, as observed by the HARMONI spectrograph on the Extremely Large Telescope, assisted by laser tomographic adaptive optics. The goal of the simulations, using the HSIM simulation tool, is to determine whether HARMONI can discern the supernova type from spectral features in the supernova spectrum. We ?nd that in a 3 h observation, covering the near-infrared H and K bands, at a spectral resolving power of ～3000, and using the 20 × 20 mas spaxel scale, we can classify Type Ia supernovae and their redshift robustly up to 80 d past maximum light (20 d in the supernova rest frame). We show that HARMONI will provide spectra at z ～ 3, which are of comparable (or better) quality to the best spectra we can currently obtain at z ～ 1, thus allowing studies of cosmic expansion rates to be pushed to substantially higher redshifts.
关键词： instrumentation: adaptive optics,instrumentation: spectrographs,galaxies: high-redshift,instrumentation: high angular resolution,supernovae: general
更新于2025-09-23 15:21:01
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Handbook of Exoplanets || ESPRESSO on VLT: An Instrument for Exoplanet Research
摘要： ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) is a VLT ultra-stable high-resolution spectrograph that will be installed in Paranal Observatory in Chile at the end of 2017 and offered to the community by 2018. The spectrograph will be located at the Combined Coudé Laboratory of the VLT and will be able to operate with one or (simultaneously) several of the four 8.2 m Unit Telescopes (UT) through four optical Coudé trains. Combining ef?ciency and extreme spectroscopic precision, ESPRESSO is expected to gaining about two magnitudes with respect to its predecessor HARPS. We aim at improving the instrumental radial velocity precision to reach the 10 cm s(cid:2)1 level, thus opening the possibility to explore new frontiers in the search for Earth-mass exoplanets in the habitable zone of quiet, nearby G to M dwarfs. ESPRESSO will be certainly an important development step toward high-precision ultra-stable spectrographs on the next generation of giant telescopes such as the E-ELT.
关键词： Planetary systems,Techniques: spectroscopic,Instrumentation: spectrographs
更新于2025-09-23 15:21:01
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Echelle++, a Fast Generic Spectrum Simulator
摘要： We present the software package, Echelle++, an open-source C++ code to simulate realistic raw spectra based on the Zemax model of any spectrograph, with a particular emphasis on cross-dispersed échelle spectrographs. Echelle++ generates realistic spectra of astronomical and calibration sources, with accurate representation of optical aberrations, the shape of the point-spread function, detector characteristics, and photon noise. It produces high-?delity spectra fast, a very important feature when testing data reduction pipelines with a large set of different input spectra, when making critical choices about order spacing in the design phase of the instrument, or while aligning the spectrograph during construction. Echelle++ also works with low-resolution, low signal-to-noise, multi-object, IFU, or long-slit spectra, for simulating a wide array of spectrographs. We chose to initially generate our own spectrograph model from the optical prescription in Zemax. Echelle++ can then be used independently, without access to commercial ray tracing software.
关键词： methods: numerical,techniques: radial velocities,instrumentation: spectrographs
更新于2025-09-23 15:19:57
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Efficient injection from large telescopes into single-mode fibres: Enabling the era of ultra-precision astronomy
摘要： Photonic technologies offer numerous advantages for astronomical instruments such as spectrographs and interferometers owing to their small footprints and diverse range of functionalities. Operating at the diffraction-limit, it is notoriously difficult to efficiently couple such devices directly with large telescopes. We demonstrate that with careful control of both the non-ideal pupil geometry of a telescope and residual wavefront errors, efficient coupling with single-mode devices can indeed be realised. A fibre injection was built within the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument. Light was coupled into a single-mode fibre operating in the near-IR (J ? H bands) which was downstream of the extreme adaptive optics system and the pupil apodising optics. A coupling efficiency of 86% of the theoretical maximum limit was achieved at 1550 nm for a diffraction-limited beam in the laboratory, and was linearly correlated with Strehl ratio. The coupling efficiency was constant to within <30% in the range 1250–1600 nm. Preliminary on-sky data with a Strehl ratio of 60% in the H-band produced a coupling efficiency into a single-mode fibre of ～50%, consistent with expectations. The coupling was >40% for 84% of the time and >50% for 41% of the time. The laboratory results allow us to forecast that extreme adaptive optics levels of correction (Strehl ratio >90% in H-band) would allow coupling of >67% (of the order of coupling to multimode fibres currently) while standard levels of wavefront correction (Strehl ratio >20% in H-band) would allow coupling of >18%. For Strehl ratios <20%, few-port photonic lanterns become a superior choice but the signal-to-noise, and pixel availability must be considered. These results illustrate a clear path to efficient on-sky coupling into a single-mode fibre, which could be used to realise modal-noise-free radial velocity machines, very-long-baseline optical/near-IR interferometers and/or simply exploit photonic technologies in future instrument design.
关键词： instrumentation: interferometers,instrumentation: high angular resolution,instrumentation: spectrographs,instrumentation: adaptive optics
更新于2025-09-19 17:15:36
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Performance of the VLT Planet Finder SPHERE
摘要： Context. The new planet finder for the Very Large Telescope (VLT), the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), just had its first light in Paranal. A dedicated instrument for the direct detection of planets, SPHERE, is composed of a polarimetric camera in visible light, the Zurich IMager POLarimeter (ZIMPOL), and two near-infrared sub-systems: the Infra-Red Dual-beam Imager and Spectrograph (IRDIS), a multi-purpose camera for imaging, polarimetry, and long-slit spectroscopy, and the integral field spectrograph (IFS), an integral field spectrograph. Aims. We present the results obtained from the analysis of data taken during the laboratory integration and validation phase, after the injection of synthetic planets. Since no continuous field rotation could be performed in the laboratory, this analysis presents results obtained using reduction techniques that do not use the angular differential imaging (ADI) technique. Methods. To perform the simulations, we used the instrumental point spread function (PSF) and model spectra of L and T-type objects scaled in contrast with respect to the host star. We evaluated the expected error in astrometry and photometry as a function of the signal to noise of companions, after spectral differential imaging (SDI) reduction for IRDIS and spectral deconvolution (SD) or principal component analysis (PCA) data reductions for IFS. Results. We deduced from our analysis, for example, that β Picb, a 12 Myr old planet of ～10 MJup and semi-major axis of 9–10 AU, would be detected with IRDIS with a photometric error of 0.16 mag and with a relative astrometric position error of 1.1 mas. With IFS, we could retrieve a spectrum with error bars of about 0.15 mag on each channel and astrometric relative position error of 0.6 mas. For a fainter object such as HR 8799d, a 13 MJup planet at a distance of 27 AU, IRDIS could obtain a relative astrometric error of 3 mas.
关键词： techniques: imaging spectroscopy,planetary systems,instrumentation: spectrographs,methods: data analysis,instrumentation: high angular resolution
更新于2025-09-19 17:15:36
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Data Reduction Pipeline of the TOU Optical Very High Resolution Spectrograph and Its sub-m?s?1?Performance
摘要： TOU is an extremely high resolution optical spectrograph (R = 100 000, 380–900 nm), which is designed to detect low-mass exoplanets using the radial velocity technique. We describe an IDL-based radial velocity (RV) data reduction pipeline for the TOU spectrograph and its performance with stable stars. This pipeline uses a least-squares fitting algorithm to match observed stellar spectra to a high-signal-to-noise template created for each star. By carefully controlling all of the error contributions to RV measurements in both the hardware and data pipeline, we have achieved ～0.9 m s?1 long-term RV precision with one of the most RV-stable stars, Tau Ceti, similar to what has been achieved with HARPS. This paper presents steps and details in our data pipeline on how to reach the sub-m s?1 RV precision and also all major error sources that contribute to the final RV measurement uncertainties. The lessons learned in this pipeline development can be applied to other environmentally controlled, very high resolution optical spectrographs to improve RV precision.
关键词： techniques: radial velocities,planets and satellites: detection,instrumentation: spectrographs,techniques: spectroscopic
更新于2025-09-19 17:15:36
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A VERSATILE TECHNIQUE TO ENABLE SUB-MILLI-KELVIN INSTRUMENT STABILITY FOR PRECISE RADIAL VELOCITY MEASUREMENTS: TESTS WITH THE HABITABLE-ZONE PLANET FINDER
摘要： Insufficient instrument thermomechanical stability is one of the many roadblocks for achieving 10 cm s?1 Doppler radial velocity precision, the precision needed to detect Earth-twins orbiting solar-type stars. Highly temperature and pressure stabilized spectrographs allow us to better calibrate out instrumental drifts, thereby helping in distinguishing instrumental noise from astrophysical stellar signals. We present the design and performance of the Environmental Control System (ECS) for the Habitable-zone Planet Finder (HPF), a high-resolution (R = 50,000) fiber-fed near-infrared (NIR) spectrograph for the 10 m Hobby–Eberly Telescope at McDonald Observatory. HPF will operate at 180 K, driven by the choice of an H2RG NIR detector array with a 1.7 μm cutoff. This ECS has demonstrated 0.6 mK rms stability over 15 days at both 180 and 300 K, and maintained high-quality vacuum (<10?7 Torr) over months, during long-term stability tests conducted without a planned passive thermal enclosure surrounding the vacuum chamber. This control scheme is versatile and can be applied as a blueprint to stabilize future NIR and optical high-precision Doppler instruments over a wide temperature range from ～77 K to elevated room temperatures. A similar ECS is being implemented to stabilize NEID, the NASA/NSF NN-EXPLORE spectrograph for the 3.5 m WIYN telescope at Kitt Peak, operating at 300 K. A [full SolidWorks 3D-CAD model] and a comprehensive parts list of the HPF ECS are included with this manuscript to facilitate the adaptation of this versatile environmental control scheme in the broader astronomical community.
关键词： instrumentation: spectrographs,techniques: radial velocities,techniques: spectroscopic
更新于2025-09-10 09:29:36
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The UVES Spectral Quasar Absorption Database (SQUAD) data release 1: the first 10 million seconds
摘要： We present the first data release (DR1) of the UVES Spectral Quasar Absorption Database (SQUAD), comprising 467 fully reduced, continuum-fitted high-resolution quasar spectra from the Ultraviolet and Visual Echelle Spectrograph (UVES) on the European Southern Observatory's Very Large Telescope. The quasars have redshifts z = 0–5, and a total exposure time of 10 million seconds provides continuum-to-noise ratios of 4–342 (median 20) per 2.5 km s?1 pixel at 5500 ?. The SQUAD spectra are fully reproducible from the raw, archival UVES exposures with open-source software, including our UVES POPLER tool for combining multiple extracted echelle exposures which we document here. All processing steps are completely transparent and can be improved upon or modified for specific applications. A primary goal of SQUAD is to enable statistical studies of large quasar and absorber samples, and we provide tools and basic information to assist three broad scientific uses: studies of damped Lyman-α systems (DLAs), absorption-line surveys, and time-variable absorption lines. For example, we provide a catalogue of 155 DLAs whose Lyman-α lines are covered by the DR1 spectra, 18 of which are reported for the first time. The H I column densities of these new DLAs are measured from the DR1 spectra. DR1 is publicly available and includes all reduced data and information to reproduce the final spectra.
关键词： instrumentation: spectrographs,line: profiles,quasars: absorption lines,cosmology: observations,cosmology: miscellaneous
更新于2025-09-10 09:29:36
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A new infrared Fabry-Pérot-based radial-velocity-reference module for the SPIRou radial-velocity spectrograph
摘要： Context. The ?eld of exoplanet research is moving towards the detection and characterization of habitable planets. These exo-Earths can be easily found around low-mass stars by using either photometric transit or radial-velocity (RV) techniques. In the latter case the gain is twofold because the signal induced by the planet of a given mass is higher due to the more favourable planet-star mass ratio and because the habitable zone lies closer to the star. However, late-type stars emit mainly in the infrared (IR) wavelength range, which calls for IR instruments. Aims. SPIRou is a stable RV IR spectrograph addressing these ambitious scienti?c objectives. As with any other spectrograph, calibration and drift monitoring is fundamental to achieve high precision. However, the IR domain su?ers from a lack of suitable reference spectral sources. Our goal was to build, test and ?nally operate a Fabry-Pérot-based RV-reference module able to provide the needed spectral information over the full wavelength range of SPIRou. Methods. We adapted the existing HARPS Fabry-Pérot calibrator for operation in the IR domain. After manufacturing and assembly, we characterized the FP RV-module in the laboratory before delivering it to the SPIRou integration site. In particular, we measured ?nesse, transmittance, and spectral ?ux of the system. Results. The measured ?nesse value of F = 12.8 corresponds perfectly to the theoretical value. The total transmittance at peak is of the order of 0.5%, mainly limited by ?bre-connectors and interfaces. Nevertheless, the provided ?ux is in line with the the requirements set by the SPIRou instrument. Although we could test the stability of the system, we estimated it by comparing the SPIRou Fabry-Pérot with the already operating HARPS system and demonstrated a stability of better than 1 m s?1 during a night. Conclusions. Once installed on SPIRou, we will test the full spectral characteristics and stability of the RV-reference module. The goal will be to prove that the line position and shape stability of all lines is better than 0.3 m s?1 between two calibration sequences (typically 24 h), such that the RV-reference module can be used to monitor instrumental drifts. In principle, the system is also intrinsically stable over longer time scales such that it can also be used for calibration purposes.
关键词： instrumentation: spectrographs,telescopes,instrumentation: interferometers,techniques: radial velocities
更新于2025-09-09 09:28:46