- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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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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New constraints on the dust surrounding HR 4796A
摘要： Context.HR 4796A is surrounded by a well-structured and very bright circumstellar disc shaped like an annulus with many interesting features: very sharp inner and outer edges, brightness asymmetries, centre o?set, and suspected distortions in the ring. Aims. We aim to constrain the properties of the dust surrounding the star HR 4796A, in particular the grain size and composition. We also want to con?rm and re?ne the morphological parameters derived from previous scattered light observations, and reveal the dust spatial extent in regions unexplored so far due to their proximity to the star. Methods. We have obtained new images in polarised light of the binary system HR 4796A and B in the Ks and L(cid:3) band with the NaCo instrument at the Very Large Telescope (VLT). In addition, we revisit two archival data sets obtained in the L(cid:3) band with that same instrument and at 2.2 μm with the NICMOS instrument on the Hubble Space Telescope. We analyse these observations with simulations using the radiative transfer code MCFOST to investigate the dust properties. We explore a grid of models with various dust compositions and sizes in a Bayesian approach. Results. We detect the disc in polarised light in the Ks band and reveal for the ?rst time the innermost regions down to 0.3(cid:3)(cid:3) along the semi-minor axis. We measure a polarised fraction of 29% ± 8% in the two disc ansae, with a maximum occurring more than 13? westwards from the ansae. A very pronounced brightness asymmetry between the north-west and south-east side is detected. This contradicts the asymmetry previously reported in all images of the disc in unpolarised light at wavelengths smaller than or equal to 2.2 μm and is inconsistent with the predicted scattered light from spherical grains using the Mie theory. Our modelling suggests the north-west side is most likely inclined towards the Earth, contrary to previous conclusions. It shows that the dust is composed of porous aggregates larger than 1 μm.
关键词： scattering,stars: individual: HR 4796A,planetary systems,instrumentation: polarimeters,instrumentation: high angular resolution
更新于2025-09-23 15:21:21
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Calibration of mixed-polarization interferometric observations
摘要： Heterodyne receivers register the sky signal on either a circular polarization basis (where it is split into left-hand and right-hand circular polarization) or a linear polarization basis (where it is split into horizontal and vertical linear polarization). We study the problem of interferometric observations performed with telescopes that observe on di?erent polarization bases, hence producing visibilities that we call “mixed basis” (i.e., linear in one telescope and circular in the other). We present novel algorithms for the proper calibration and treatment of such interferometric observations and test our algorithms with both simulations and real data. The use of our algorithms will be important for the optimum calibration of forthcoming observations with the Atacama Large Mm/submm Array (ALMA) in very-long-baseline interferometry (VLBI) mode. Our algorithms will also allow us to optimally calibrate future VLBI observations at very high data rates (i.e., wide bandwidths), where linear-polarization feeds will be preferable at some stations, to overcome the polarimetric limitations due to the use of quarter-wave plates.
关键词： instrumentation: interferometers – techniques: interferometric – techniques: polarimetric
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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Operation and performance of the JUNGFRAU photon detector during first FEL and synchrotron experiments
摘要： JUNGFRAU is a hybrid pixel photon detector developed at the Paul Scherrer Institut for free electron laser (FEL) and synchrotron applications. A charge integrating detector, JUNGFRAU features three automatically switching gains per pixel which adjust the amplification factor to the amount of deposited charge. This enables single photon sensitivity, while ensuring a dynamic range over four orders of magnitude. Each detector module consists of eight 256 × 256 pixel ASICs bump-bonded to a single 320 μm thick silicon sensor, resulting in half a million pixels of 75 μm pitch arranged in 1024 × 512 arrays for a sensitive area of approximately 8 × 4 cm2. Modules can be combined in various configurations to produce larger systems. These proceedings present the required steps, both operational and in terms of data processing, necessary to perform experiments with the JUNGFRAU detector. This includes the calculation and application of pedestal and gain corrections and the geometric arrangement of the recorded image. Examples of these techniques in action will be presented from the first experiments performed with JUNGFRAU detectors; the pilot experiment of the SwissFEL Bernina beamline and proof-of-principle macromolecular crystallography measurements from the X06SA beamline of the Swiss Light Source. Successful operation and data processing methods from FEL and synchrotron facilities will be compared and contrasted, and experience of overcoming challenges in the two scenarios will be shared. Finally, the capability of JUNGFRAU for FEL and synchrotron applications will be demonstrated.
关键词： Instrumentation for synchrotron radiation accelerators,X-ray detectors,Instrumentation for FEL
更新于2025-09-23 15:21:01
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The EBEX Balloon-borne Experiment—Detectors and Readout
摘要： EBEX was a long-duration balloon-borne experiment to measure the polarization of the cosmic microwave background. The experiment had three frequency bands centered at 150, 250, and 410 GHz and was the first to use a kilopixel array of transition edge sensor bolometers aboard a balloon platform. We describe the design and characterization of the array and the readout system. From the lowest to highest frequency, the median measured detectors' average thermal conductances were 39, 53, and 63 pW/K, the medians of transition temperatures were 0.45, 0.48, and 0.47 K, and the medians of normal resistances were 1.9, 1.5, and 1.4 Ω; we also give the measured distributions. With the exception of the thermal conductance at 150 GHz, all measured values are within 30% of their design. We measure median low-loop-gain time constants τ0 = 88, 46, and 57 ms. Two measurements of bolometer absorption efficiency gave results consistent within 10% and showing high (～0.9) efficiency at 150 GHz and medium (～0.35 and ～0.25) efficiency at the two higher bands. We measure a median total optical power absorbed of 3.6, 5.3, and 5.0 pW. EBEX pioneered the use of the digital version of the frequency domain multiplexing system. We multiplexed the bias and readout of 16 bolometers onto two wires. The median per-detector noise-equivalent temperatures are 400, 920, and 14,500 mK. We compare these values to our preflight predictions and to a previous balloon payload. We discuss the sources of excess noise and the path for a future payload to make full use of the balloon environment.
关键词： cosmology: observations,instrumentation: polarimeters,cosmic background radiation,balloons,instrumentation: detectors
更新于2025-09-23 15:21:01
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Suppressing beam deflections by introducing phosphorous in the GaAs-based terahertz MEMS bolometers
摘要： This paper presents a novel and analytical approach to identifying a lightning strike after it has struck an overhead transmission line. The identi?cation method is mainly based on the traveling waves’ time-domain parameters, such as polarity, amplitude, and half-wavelength. The main differences in these parameters across different strike types are analyzed. Subsequently, a robust identi?cation algorithm is proposed. An instrumentation system is implemented to verify the algorithm. The overall performances of the instrumentation system and the methodology are demonstrated using an on-site application with excellent results.
关键词： instrumentation system,current traveling wave,half-wave length,shielding failure,Back ?ashover,amplitude,polarity
更新于2025-09-23 15:21:01
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[IEEE 2019 Innovations in Power and Advanced Computing Technologies (i-PACT) - Vellore, India (2019.3.22-2019.3.23)] 2019 Innovations in Power and Advanced Computing Technologies (i-PACT) - High Performance Visible-Range Photodetector for Wide-Bandwidth Applications
摘要： This paper presents a novel and analytical approach to identifying a lightning strike after it has struck an overhead transmission line. The identi?cation method is mainly based on the traveling waves’ time-domain parameters, such as polarity, amplitude, and half-wavelength. The main differences in these parameters across different strike types are analyzed. Subsequently, a robust identi?cation algorithm is proposed. An instrumentation system is implemented to verify the algorithm. The overall performances of the instrumentation system and the methodology are demonstrated using an on-site application with excellent results.
关键词： instrumentation system,current traveling wave,half-wave length,shielding failure,Back ?ashover,amplitude,polarity
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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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || SPECTROPHOTOMETRY/Diode Array ☆
摘要： Diode array spectrometry represents a particular approach for characterizing the result of the interaction between electromagnetic radiation and the sample, based on simultaneous measurement of light intensity over small spectral intervals having equal width. This is achieved through the following sequential stages, as schematically shown in Figs. 1 and 2D: a. interaction between the polychromatic beam and the sample; b. spatial dispersion of the transmitted (eventually reflected or emitted) radiation according to wavelength on multiple channels of equal widths, by means of a fixed optical element; c. imaging the dispersed radiation in a focal plane; and d. (quasi)simultaneous sampling of the dispersed radiation interval using photosensitive detectors, precisely positioned in the focal plane.
关键词： photodiode principle,Diode array spectrometry,concave diffraction gratings,spectrophotometry,instrumentation
更新于2025-09-23 15:21:01