Cross-correlation Technique Research Articles

Compact optical fiber sensor based on Vernier effect with speckle patterns.

We propose a Vernier effect-based sensor for temperature and salinity measurements. This sensor utilizes the correlation speckle pattern generated by spatial multimode interference and has undergone testing to validate its effectiveness. The speckle demodulation method is used to solve the problem of inconsistent envelope measurement when tracking with different upper and lower envelopes. The device consists of two Fabry Perot interferometers (FPIs) created by connecting hole core fiber (HCF) and erbium-doped fiber (EDF) in series. The speckle image produced by the interferometers is analyzed using the Zero means normalized cross-correlation (ZNCC) technique. The ZNCC value demonstrates a linear relationship with salinity and temperature, allowing for the measurement of these parameters. The sensor exhibits a temperature detection sensitivity of -0.0224 /°C and a salinity detection sensitivity of -0.0439/%. The sensor offers several advantageous features, including its compact size, low-cost manufacturing, high sensitivity, stability, and convenient reflection measurements. These characteristics make it a valuable tool for various applications. The proposed Vernier effect-based temperature and salinity sensor shows great potential for simultaneous monitoring and measurement of temperature and salinity in environments such as marine settings or industrial processes where accurate control of these parameters is crucial.

ExoGemS High-resolution Transmission Spectroscopy of WASP-76b with GRACES

We present high-resolution transmission spectroscopy of WASP-76b with Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES)/Gemini North obtained as part of the ExoGemS survey. With a broad spectral range of 400–1050 nm and a relatively high resolution of ∼66,000, these observations are particularly well suited to searching for atomic and molecular atmospheric species via the Doppler cross-correlation technique. We recover absorption features due to neutral iron (Fe i), sodium (Na i), and ionized calcium (Ca ii) at high significance (>5σ), and investigate possible atmospheric temperatures and wind speeds. We also report tentative (>3σ) detections of Li i, K i, Cr i, and V i in the atmosphere of WASP-76b. Finally, we report nondetections of a number of other species, some of which have previously been detected with other instruments. Through model injection/recovery tests, we demonstrate that many of these species are not expected to be detected in our observations. These results allow us to place GRACES and the ExoGemS survey in context with other high-resolution optical spectrographs.

Detection of Carbon Monoxide in the Atmosphere of WASP-39b Applying Standard Cross-correlation Techniques to JWST NIRSpec G395H Data

Carbon monoxide was recently reported in the atmosphere of the hot Jupiter WASP-39b using the NIRSpec PRISM transit observation of this planet, collected as part of the JWST Transiting Exoplanet Community Early Release Science Program. This detection, however, could not be confidently confirmed in the initial analysis of the higher-resolution observations with NIRSpec G395H disperser. Here we confirm the detection of CO in the atmosphere of WASP-39b using the NIRSpec G395H data and cross-correlation techniques. We do this by searching for the CO signal in the unbinned transmission spectrum of the planet between 4.6 and 5.0 μm, where the contribution of CO is expected to be higher than that of other anticipated molecules in the planet’s atmosphere. Our search results in a detection of CO with a cross-correlation function (CCF) significance of 6.6σ when using a template with only 12C16O lines. The CCF significance of the CO signal increases to 7.5σ when including in the template lines from additional CO isotopologues, with the largest contribution being from 13C16O. Our results highlight how cross-correlation techniques can be a powerful tool for unveiling the chemical composition of exoplanetary atmospheres from medium-resolution transmission spectra, including the detection of isotopologues.

Benefits of software beamforming for ultrasonic inspections

Nondestructive testing (NDT) is used in more and more industries and inspection techniques must constantly adapt to complex materials (coarse grained materials, composites, etc.), defects (corrosion, fatigue crack, HTHA, etc.) or new inspection standards. Ultrasonic imaging methods have long been limited by low data throughput and a small number of transducers, but this is no longer the case with nowadays electronic devices and computers which enable large amounts of raw data to be acquired and processed in real time. The Delay-and-Sum (DAS) algorithm, which has been used almost automatically in many applications over the past few years, is now outperformed by advanced processing methods. In this context, this article presents few real-time advanced reconstruction techniques that enhance the quality of ultrasonic images on typical industrial applications. The first example concerns coherence beamformers such as Phase Coherence Imaging (PCI) which exploit the phase information of the signals. This type of method proves to be highly effective in detecting diffraction echoes from crack-like defects or in improving contrast and resolution of images from corroded samples inspections. The second example uses cross-correlation techniques that have been known for years to improve detection in various fields. Correlating the data with the transmitted signal reduces electronic noise and improves signal-to-noise ratio. This application also benefits from recent progress of ultrasonic devices that are able to modulate complex excitation signals in emission. This type of method is very promising for the inspection of attenuative materials and coarse-grained steels.

Velocity Changes Associated to the 2019 Ambon 6.5 Mw Earthquake Using Ambient Seismic Noise

Seismic velocity changes which occurred before, during and after large magnitude earthquake carry information about damage fault surrounding the area. Research focused on Ambon 6.5 Mw earthquake on September 26, 2019. We use ambient noise cross-correlation technique to compute empirical Green’s Function between station pairs from January to December 2019. We use doublet method to determine perturbation calculated in frequency domain by using Moving Windows Cross Spectrum in frequency between 0.1 to 1.0 Hz. Our results show no obvious significant velocity change before the mainshock. Velocity fluctuation average about ±0.1% caused by non-isotropic of noise source around the area. Sudden velocity decrease occurred and reached average value of -0.35% in 7 days after mainshock. After reaching its lowest value, velocity gradually increased about +0.4% in 14 days. Velocity fluctuations about ±0.2% also occurred for three months after the earthquake which may caused by the aftershocks around the earthquake epicentre. Following the large magnitude mainshock, velocity reduction may be induced by cracks opening and fractures due to deformation. While the velocity increase may caused by post-seismic relaxation due to elastic behaviour and crack healing of the fault throughout the surrounding region.

Influence of ultrasound machine settings on quantitative measures derived from spatial frequency analysis of muscle tissue

BackgroundUltrasound is a powerful tool for diagnostic purposes and provides insight into both normal and pathologic tissue structure. Spatial frequency analysis (SFA) methods characterize musculoskeletal tissue organization from ultrasound images. Both sonographers in clinical imaging and researchers may alter a minimized range of ultrasound settings to optimize image quality, and it is important to know how these small adjustments of these settings affect SFA parameters. The purpose of this study was to investigate the effects of making small adjustments in a typical default ultrasound machine setting on extracted spatial frequency parameters (peak spatial frequency radius (PSFR), Mmax, Mmax%, and Sum) in the biceps femoris muscle.MethodsLongitudinal B-mode images were collected from the biceps femoris muscle in 36 participants. The window depth, foci locations, and gain were systematically adjusted consistent with clinical imaging procedures for a total of 27 images per participant. Images were analyzed by identifying a region of interest (ROI) in the middle portion of the muscle belly in a template image and using a normalized two-dimensional cross-correlation technique between the template image and subsequent images. The ROI was analyzed in the frequency domain using conventional SFA methods. Separate linear mixed effects models were run for each extracted parameter.ResultsPSFR was affected by modifications in focus location only (p < 0.001) with differences noted between all locations. Mmax% was influenced by the interaction of gain and focus location (p < 0.001) but was also independently affected by increasing window depth (p < 0.001). Both Mmax and Sum parameters were sensitive to small changes in machine settings with the interaction of focus location and window depth (p < 0.001 for both parameters) as well as window depth and gain (p < 0.001 for both) influencing the extracted values.ConclusionsFrequently adjusted imaging settings influence some SFA statistics. PSFR and Mmax% appear to be most robust to small changes in image settings, making them best suited for comparison across individuals and between studies, which is appealing for the clinical utility of the SFA method.

High-resolution emission spectroscopy retrievals of MASCARA-1b with CRIRES+: strong detections of CO, H2O, and Fe emission lines and a C/O consistent with solar

ABSTRACT The characterization of exoplanet atmospheres has proven to be successful using high-resolution spectroscopy. Phase curve observations of hot/ultra-hot Jupiters can reveal their compositions and thermal structures, thereby allowing the detection of molecules and atoms in the planetary atmosphere using the cross-correlation technique. We present pre-eclipse observations of the ultra-hot Jupiter, MASCARA-1b, observed with the recently upgraded CRIRES+ high-resolution infrared spectrograph at the VLT. We report a detection of Fe (≈ 8.3σ) in the K-band and confirm previous detections of CO (&amp;gt;15σ) and H2O (&amp;gt;10σ) in the day-side atmosphere of MASCARA-1b. Using a Bayesian inference framework, we retrieve the abundances of the detected species and constrain planetary orbital velocities, T–P profiles, and the carbon-to-oxygen ratio (C/O). A free retrieval results in an elevated CO abundance ($\log _{10}(\chi _{\rm {{}^{12}CO}}) = -2.85^{+0.57}_{-0.69}$), leading to a supersolar C/O ratio. More realistically, allowing for vertically-varying chemistry in the atmosphere by incorporating a chemical-equilibrium model results in a C/O of $0.68^{+0.12}_{-0.22}$ and a metallicity of $[\rm M/H] = 0.62^{+0.28}_{-0.55}$, both consistent with solar values. Finally, we also report a slight offset of the Fe feature in both Kp and vsys that could be a signature of atmospheric dynamics. Due to the 3D structure of exoplanet atmospheres and the exclusion of time/phase dependence in our 1D forward models, further follow-up observations and analysis are required to confirm or refute this result.

Proof of Concept of the Use of the Parametric Effect in Two Media with Application to Underwater Acoustic Communications

Nonlinear acoustics offers a new range of acoustic applications that are currently being exploited. The parametric nonlinear effect—the occurrence of low frequencies with modulated high-frequency emission—is of particular interest. This work provides a systematic exposition of the theoretical framework on which the so-called parametric nonlinear effect is based. In relation to this behavior is an analytical discussion of how to solve the problem for two cases: (i) nonlinear behavior with modulation, and (ii) parametric emission of two monochromatic waves (bi-frequency). Subsequently, parametric emission experiments were carried out in air and water using the same transducer to compare the results with those obtained theoretically. In this sense, directivity and attenuation measurements are obtained. Conclusively, this research offers a proof of concept for underwater acoustic communications. It is characterized by the transmission of a binary sequence through Frequency Shift Keying (FSK) modulation, and the subsequent decoding of each received bit (either 1 or 0) utilizing advanced signal processing with the cross-correlation technique. This paper accentuates the significant potential of employing the parametric effect for specialized communication applications.

Evaluating similarity measure for multimodal 3D to 2D registration

The 3D to 2D registration technique in spine surgery is vital to aid surgeons in avoiding the wrong site surgery by estimating the vertebral pose. The vertebral poses are estimated by generating the spatial correspondence relationship between pre-operative MR with intra-operative x-ray images, then evaluated using a similarity measure. Different similarity measures are used in 3D to 2D registration techniques to assess the spatial correspondence between the pre-operative and intra-operative images. However, to evaluate the registration performance of the similarity measures, the proposed framework employs three different similarity measures: Binary Image Matching, Dice Coefficients, and Normalized Cross-correlation technique to compare the images based on pixel positions. The registration accuracy of the proposed similarity measures is compared based on the mean Target Registration Error, mean Iteration Times, and success rate. In the absence of simulated test images, the experiment is conducted on the simulated AP and Lateral test images. The experiment conducted on the simulated test images shows that all three similarity measures work well for the feature based 3D to 2D registration in that BIM gives better results. The experiment also indicates high registration accuracy when the initial displacements are varied up to ±20 mm and ±100 of the translational and rotational parameters, respectively, for three similarity measures.

Automatic note generator for Javanese gamelan music accompaniment using deep learning

Javanese gamelan is a traditional form of music from Indonesia with a variety of styles and patterns. One of these patterns is the harmony music of the Bonang Barung and Bonang Penerus instruments. When playing gamelan, the resulting patterns can vary based on the music’s rhythm or dynamics, which can be challenging for novice players unfamiliar with the gamelan rules and notation system, which only provides melodic notes. Unlike in modern music, where harmony notes are often the same for all instruments, harmony music in Javanese gamelan is vital in establishing the character of a song. With technological advancements, musical composition can be generated automatically without human participation, which has become a trend in music generation research. This study proposes a method to generate musical accompaniment notes for harmony music using a bidirectional long-term memory (BiLSTM) network and compares it with recurrent neural network (RNN) and long-term memory (LSTM) models that use numerical notation to represent musical data, making it easier to learn the variations of harmony music in Javanese gamelan. This method replaces the gamelan composer in completing the notation for all the instruments in a song. To evaluate the generated harmonic music, note distance, dynamic time warping (DTW), and cross-correlation techniques were used to measure the distance between the system-generated results and the gamelan composer's creations. In addition, audio features were extracted and used to visualize the audio. The experimental results show that all models produced better accuracy results when using all features of the song, reaching a value of around 90%, compared to using only 2 features (rhythm and note of melody), which reached 65-70%. Furthermore, the BiLSTM model produced musical harmonies that were more similar to the original music (+93%) than those generated by the LSTM (+92%) and RNN (+90%). This study can be applied to performing Javanese gamelan music.

Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b

We present Keck Planet Imager and Characterizer (KPIC) high-resolution (R ∼35,000) K-band thermal emission spectroscopy of the ultrahot Jupiter WASP-33b. The use of KPIC’s single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We retrieve the dayside emission spectrum with a nested-sampling pipeline, which fits for orbital parameters, the atmospheric pressure–temperature profile, and the molecular abundances. We strongly detect the thermally inverted dayside and measure mass-mixing ratios for CO (), H2O (), and OH (), suggesting near-complete dayside photodissociation of H2O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of , consistent with the accretion of high-metallicity gas near the CO2 snow line and post-disk migration or with accretion between the soot and H2O snow lines. We also find tentative evidence for 12CO/13CO ∼ 50, consistent with values expected in protoplanetary disks, as well as tentative evidence for a metal-enriched atmosphere (2–15 × solar). These observations demonstrate KPIC’s ability to characterize close-in planets and the utility of KPIC’s improved instrumental stability for cross-correlation techniques.

Determination of Maximum Accuracy of Concrete Textures as Natural Targets for Movement Tracking Through DIC

The use of natural targets is one of the obstacles to the extensive use of digital image cross-correlation for measuring movements in civil structures. Long distance measurement through image and without access to the structure itself, brings results in an improvement in accessibility, being the procedure cheaper and safer than common methods that require direct access to the measuring point. One of the most used materials in construction is concrete. Therefore, it is important to analyze its performance when using image cross-correlation. In this work, we have made a series of concrete probes with different production characteristics to have a representative variety of concrete surfaces. With them, we have studied their floor error in a cross-correlation procedure using different illumination and blur conditions, to evaluate the influence of those parameters on the results. All results are compared to those obtained using the conventional texture for image cross-correlation techniques, that is a pseudo-speckle target. All experiments are done in laboratory conditions to control all variables involved and to avoid the influence of other variables linked to open air conditions, such as atmospheric disturbances. As a result, we have determined the best conditions to use the natural concrete texture and we have quantified that using this texture leads to a decrease in the accuracy of the results from two to three times the one obtained with a typical pseudo-speckle texture.

Argon, neon, and nitrogen impurity transport in the edge and SOL regions of a tokamak

Numerical simulations of the interchange plasma turbulence in the presence of medium-Z impurities (N2, Ne, and Ar) seeding have been performed using BOUT++. These simulation results are used to study the impurity transport mechanism in the edge and scrape-off layer (SOL) regions. An analytical relation for the impurity ion density with the vorticity, sources and sinks, and mass to charge ratio has also been derived. Simulation shows that Ar+ moves more strongly inward compared to N+ and Ne+ that has been verified from the analytical relation. The most abundant species move in both the inward and outward directions, but on average, they mainly move outward. These behaviors have been confirmed using cross-correlation techniques. The inward transport or negative flux of the impurity ions is found directly associated with the monopolar density holes in the presence of the electron temperature gradient, whereas the outward transport is associated with the plasma blobs. The inward impurity transport has been analyzed using hole fraction analysis. The percentages of Ar+, Ne+, and N+ ions of their total impurity densities transported inward mainly through the avalanche events of the turbulent plasma are presented.

EI Eridani: A star under the influence

Context. Homogeneous photometric time series spanning decades provide a unique opportunity to study the long-term cyclic behavior of active spotted stars such as our target EI Eridani. In addition, with ultraprecise space photometry data, it is possible to investigate the accompanying flare activity in detail. However, the rotation period of ≈2 days for EI Eri makes it impossible to achieve time-resolved surface images from a single ground-based observing site. Therefore, for this purpose, spectroscopic data from a multi-site observing campaign are needed. Aims. We use our photometric time series of more than 40 yr to analyze the long-term behavior of EI Eri. We investigate flare activity using photometric data obtained with the Transiting Exoplanet Survey Satellite (TESS). The MUlti-SIte Continuous Spectroscopy (MUSICOS) campaign in 1998 was designed to achieve high-resolution, multi-wavelength spectroscopic observations from many sites around the globe, which meant that uninterrupted phase coverage of EI Eri became available. We use these data to reconstruct successive surface-temperature maps of the star in order to study the changes of starspots on a very short timescale. Methods. We used long-term seasonal period analysis of our photometric time series to study changes in the rotational period. We also applied short-term Fourier-transform to look for activity cycle-like changes. We also studied the phase and frequency distribution of hand-selected flares. We applied our multi-line Doppler imaging code to reconstruct four consecutive Doppler images. These images were also used to measure surface differential rotation with our cross-correlation technique. In addition, we carried out tests to demonstrate how Doppler imaging is affected by the fact that the data came from several different instruments with different spectral resolutions. Results. Seasonal period analysis of the light curve reveals a smooth, significant change in period, possibly indicating the evolution of active latitudes. Temperature curves from B − V and V − I show slight differences, indicating the activity of EI Eri is spot dominated. Short-term Fourier transform reveals smoothly changing cycles of between 4.5 and 5.5 yr and of between 8.9 and 11.6 yr. The time-resolved spotted surface of EI Eri from Doppler imaging enabled us to follow the evolution of the different surface features. Cross-correlating the consecutive Doppler maps reveals surface shear of α = 0.036 ± 0.007. Our tests validate our approach and show that the surface-temperature distribution is adequately reconstructed by our method. The tests also indicate how accurately the cross-correlation method can reproduce the surface shear as a function of the spectral resolution.

En echelon faults reactivated by wastewater disposal near Musreau Lake, Alberta

SUMMARY We use machine-learning and cross-correlation techniques to enhance earthquake detectability by two magnitude units for the earthquake sequence near Musreau Lake, Alberta, which is induced by wastewater disposal. This deep catalogue reveals a series of en echelon ∼N–S oriented strike-slip faults that are favourably oriented for reactivation. These faults require only ∼0.6 MPa overpressure for triggering to occur. Earthquake activity occurs in bursts, or episodes; episodes restricted to the largest fault tend to have earthquakes starting near the southern end (distant from injectors) and progressing northwards (towards the injectors). While most events are concentrated along these ∼N–S oriented faults, we also delineate smaller faults. Together, these findings suggest pore pressure as the triggering mechanism, where a time-dependent increase in pore pressure likely caused these faults to progressively reawaken. Analysis of the ‘next record-breaking event’, a statistical model that forecasts the sequencing of earthquake magnitudes, suggests that the next largest event would be ML ∼4.3. The seismically illuminated length of the largest fault indicates potential magnitudes as large as Mw 5.3.

Maximum power point tracking using cross-correlation algorithm for PV system

This paper suggests an online, rapid, dynamic, and pragmatic cross-correlation (CC) technique to effectively realize maximum power point tracking (MPPT) of the photovoltaic (PV) array. The PV voltage and current are extracted, averaged, and the rate of change of the power and terminal voltage dynamics are integrally cross-correlated to regulate the duty ratio of the converter. According to this approach, the maximum power point (MPP) is defined in terms of the polarity of the CC coefficient (rcc). If the CC coefficient is positive, the operating point is at the left of the MPP, while a negative CC coefficient indicates that the operating point is located at the right of the MPP, otherwise, the MPP is attained at zero CC coefficient with lower steady-state fluctuations. In this regard, a tracking optimization can be realized with a confined drift either under gradual or step solar irradiance changes. The proposed CC technique quickly converges to the MPP without the identification of PV array parameters. Besides, the proposed CC tracking algorithm tracks MPP with wide-range small step-size iterations since the search area is restricted to the vicinity of the MPP rather than the entire PV curve. Moreover, the proposed technique is featured by robustness against system parameters and load variations with simple hardware implementation as compared to several existing techniques. The effectiveness of the proposed technique is thoroughly explored via time-domain, experimental, and hardware-in-loop investigations and meanwhile compared to the two most popular techniques: perturb and observe (P&O) and incremental conductance (INC) methods, for both gradual and step irradiance changes and also shadow effects. The performed case studies revealed superior behavior, rapid convergence with high tracking efficiency and low oscillations, and overriding capability of the influence of the system parameters and load variations.

There’s More to Life than O2: Simulating the Detectability of a Range of Molecules for Ground-based, High-resolution Spectroscopy of Transiting Terrestrial Exoplanets

Within the next decade, atmospheric O2 on Earth-like M-dwarf planets may be accessible with visible–near-infrared (NIR), high-spectral-resolution, ground-based extremely large telescope (ELT) instruments. However, the prospects for using ELTs to detect environmental properties that provide context for O2 have not been thoroughly explored. Additional molecules may help indicate planetary habitability, rule out abiotically generated O2, or reveal alternative biosignatures. To understand the accessibility of environmental context using ELT spectra, we simulate high-resolution transit transmission spectra of previously generated evolved terrestrial atmospheres. We consider inhabited preindustrial and Archean Earth–like atmospheres, and lifeless worlds with abiotic O2 buildup from CO2 and H2O photolysis. All atmospheres are self-consistent with M2V–M8V dwarf host stars. Our simulations include explicit treatment of systematic and telluric effects to model high-resolution spectra for Giant Magellan Telescope (GMT), Thirty Meter Telescope (TMT), and European ELT (E-ELT) configurations for systems 5 and 12 pc from Earth. Using the cross-correlation technique, we determine the detectability of major species in these atmospheres: O2, O3, CH4, CO2, CO, H2O, and C2H6. Our results suggest that CH4 and CO2 are the most accessible molecules for terrestrial planets transiting a range of M-dwarf hosts using an E-ELT-, TMT-, or GMT-sized telescope, and that the O2 NIR and H2O 0.9 μm bands may also be accessible with more observation time. Although this technique still faces considerable challenges, the ELTs will provide access to the atmospheres of terrestrial planets transiting earlier-type M-dwarf hosts that may not be possible using JWST.

Shark bycatch of the acoupa weakfish, Cynoscion acoupa (Lacèpede, 1801), fisheries of the Amazon Shelf

In recent years, the populations of many shark species have been depleted drastically around the world. In the present study, we analyzed the shark bycatch in the monthly landing data of the acoupa weakfish (Cynoscion acoupa) gillnet fisheries of the state of Pará, on the northern coast of Brazil, between January 1995 and December 2007. Based on 4,659 landings, we estimated that a total of 1,972.50 tons of shark were taken as bycatch during the study period. The acoupa weakfish fisheries operate on the Amazon Shelf, an important fishing ground, and we analyzed the shark landings in relation to the Amazon River Discharge anomaly (ARD) and the climatic variability in the Atlantic Ocean. We applied cross-correlation, cross-wavelet, wavelet coherence, and redundancy analysis techniques to the analysis of the data time series. The shark bycatch landings peaked between 1998 and 2000, a period associated with an increase in fishing effort by the acoupa weakfish fisheries, in particular during the dry season of the Amazon basin. The cross-correlation analysis indicated that shark landings were associated with Sea Surface Temperatures (SSTs), the characteristics of the wind, and the Atlantic Multidecadal Oscillation (AMO), while the fishing effort of the acoupa weakfish fisheries was associated with the meridional wind component, the AMO, and the ARD. The cross-wavelet and coherence wavelet analyses indicated that environmental variability was linked systematically with shark landings and acoupa weakfish fishing effort. We observed a phase change in this signal between 1998 and 2000, due to a strong and persistent La Niña event. Despite the resistance from the fishing industry, development and deployment of devices designed to reduce bycatch should be incentivized in order to reduce the unintentional capture of endangered species such as sharks. The findings of the present study highlight the importance of a continuous and accurate fishery database, and the need for continuous fishery statistics to ensure adequate management practices. Adequate public fishery management policies must be implemented urgently to guarantee the survival of shark species, with the effective participation of all the actors involved in the process, including managers, researchers, and fishers.

CRIRES+ detection of CO emissions lines and temperature inversions on the dayside of WASP-18b and WASP-76b

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 (υeq) in the retrieval when analyzing the line profile broadening. The obtained υeq 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.

Recovering Cosmic Microwave Background Polarization Signals with Machine Learning

Primordial B-mode detection is one of the main goals of current and future cosmic microwave background (CMB) experiments. However, the weak B-mode signal is overshadowed by several Galactic polarized emissions, such as thermal dust emission and synchrotron radiation. Subtracting foreground components from CMB observations is one of the key challenges in searching for the primordial B-mode signal. Here, we construct a deep convolutional neural network (CNN) model, called CMBFSCNN (Cosmic Microwave Background Foreground Subtraction with CNN), which can cleanly remove various foreground components from simulated CMB observational maps at the sensitivity of the CMB-S4 experiment. Noisy CMB Q (or U) maps are recovered with a mean absolute difference of 0.018 ± 0.023 μK (or 0.021 ± 0.028 μK). To remove the residual instrumental noise from the foreground-cleaned map, inspired by the needlet internal linear combination method, we divide the whole data set into two “half-split maps,” which share the same sky signal, but have uncorrelated noise, and perform a cross-correlation technique to reduce the instrumental noise effects at the power spectrum level. We find that the CMB EE and BB power spectra can be precisely recovered with significantly reduced noise effects. Finally, we apply this pipeline to current Planck observations. As expected, various foregrounds are cleanly removed from the Planck observational maps, with the recovered EE and BB power spectra being in good agreement with the official Planck results.