Flare Shape Research Articles

Stellar flare morphology with TESS across the main sequence

Stellar flares are abundant in space photometric light curves. As they are now available in large enough numbers, the statistical study of their overall temporal morphology is timely. We use light curves from the Transiting Exoplanet Survey Satellite (TESS) to study the shapes of stellar flares beyond a simple parameterization by duration and amplitude, and we reveal possible connections to astrophysical parameters. We retrained and used the long-short term memory neural network to find stellar flares in 2-min cadence TESS light curves from the first five years of the mission (sectors 1--69). We scaled these flares to a comparable standard shape and used principal component analysis to describe their temporal morphology in a concise way. We investigated how the flare shapes change along the main sequence and tested whether individual flares hold any information about their host stars. We also applied similar techniques to solar flares, using extreme ultraviolet irradiation time series. Our final catalog contains ∼ 120,000 flares on ∼ 14,000 stars. Due to the strict filtering and the final manual vetting, this sample contains virtually no false positives, although at the expense of reduced completeness. Using this flare catalog, we detected a dependence of the average flare shape on the spectral type. These changes are not apparent for individual flares; they only appear when averaging thousands of events. We find no strong clustering in the flare shape space. We have created new analytical flare templates for different types of stars, and we present a technique to sample realistic flares and a method to locate flares with similar shapes. The flare catalog along with the extracted flare shapes and the data used to train are publicly available.

Preparing for the Early eVolution Explorer: Characterizing the Photochemical Inputs and Transit Detection Efficiencies of Young Planets Using Multiwavelength Flare Observations by TESS and Swift

Abstract Ultraviolet flare emission can drive photochemistry in exoplanet atmospheres and even serve as the primary source of uncertainty in atmospheric retrievals. Additionally, flare energy budgets are not well understood due to a paucity of simultaneous observations. We present new near-UV (NUV) and optical observations of flares from three M dwarfs obtained at 20 s cadence with Swift and the Transiting Exoplanet Survey Satellite (TESS), along with a reanalysis of flares from two M dwarfs in order to explore the energy budget and timing of flares at NUV-optical wavelengths. We find a 9000 K blackbody underestimates the NUV flux by ≥2× for 54 ± 14% of flares and 14.8× for one flare. We report time lags between the bands of 0.5–6.6 minutes and develop a method to predict the qualitative flare shape and time lag to 36% ± 30% accuracy. The scatter present in optical-NUV relations is reduced by a factor of 2.0 ± 0.6 when comparing the total NUV energy with the TESS energy during the FWHM duration due to the exclusion of the T eff ≈ 5000 K tail. We show the NUV light curve can be used to remove flares from the optical light curve and consistently detect planets with 20% smaller transits than is possible without flare detrending. Finally, we demonstrate a 10× increase in the literature number of multiwavelength flares with the Early eVolution Explorer (EVE), an astrophysics Small Explorer concept to observe young clusters with simultaneous NUV and optical bands in order to detect young planets, assess their photochemical radiation environments, and observe accretion.

54‐1: Development of UDC Image Restoration Technology Using Space Variant CNN

With the continuous evolution of mobile device technologies, the integration of under‐display cameras has emerged as a groundbreaking innovation in the pursuit of bezel‐less and immersive visual experiences. As this technology becomes increasingly prevalent, it introduces a unique set of challenges, particularly in the realm of photography. In particular, the flare cannot be restored by conventional image processing due to saturated pixels. Therefore, a deep learning network capable of restoring such deterioration is proposed. The network is trained by a synthetic datasets generated by accurate optical simulation. However, the distortion of the camera lens distorts the shape of flare differently depending on its position in the photo, and it degrades restore quality. In this paper, we propose space‐variant CNN for solving distortion problem.

Giant electrocaloric effect and high-field electrostrictive properties in Ba(Ti1−xSnx)O3 ceramics

One of the emerging solid-state refrigeration technologies to replace classic compression refrigeration is electrocaloric refrigeration, which has the advantages of high energy conversion efficiency, easy miniaturization, eco-friendliness, and low cost. In this paper, Ba(Ti1−xSnx)O3 (BTSn) ceramics with x = 0.02–0.08 were prepared by a solid-state reaction route. The structural, dielectric, ferroelectric, electrocaloric as well as electrostrictive characteristics were thoroughly examined. Our results show that the dielectric peaks correlated to the maximal permittivity move towards to low temperature direction when the Sn4+ concentration gradually increases, and a phase diagram of BTSn based on the dielectric characteristics is given. More importantly, in the x = 0.04 ceramic sample synthesized by the viscous polymer process, a giant adiabatic temperature change (ΔT) of 6.36 K with a temperature range of 25 °C at 200 kV/cm is achieved. Typically flare shape electrostrain curves accompanying with small hysteresis are observed in all studied compositions. The average electrostrictive coefficient Q33 varies within 0.0257–0.0306 m4/C2 at a temperature region from 30 to 160 °C, indicating temperature-insensitive and composition-insensitive characteristics. This research shows that a significant electrocaloric effect can be achieved in BTSn ceramics through high electric field, and would provide a strategy for boosting the electrocaloric effect in other systems.

General relativistic effects and the near-infrared and X-ray variability of Sgr A* I

The near-infrared (NIR) and X-ray emission of Sagittarius A* shows occasional bright flares that are assumed to originate from the innermost region of the accretion flow. We identified 25 4.5 μm and 24 X-ray flares in archival data obtained with the Spitzer and Chandra observatories. With the help of general relativistic ray-tracing code, we modeled trajectories of “hot spots” and studied the light curves of the flares for signs of the effects of general relativity. Despite their apparent diversity in shape, all flares share a common, exponential impulse response, a characteristic shape that is the building block of the variability. This shape is symmetric, that is, the rise and fall times are the same. Furthermore, the impulse responses in the NIR and X-ray are identical within uncertainties, with an exponential time constant τ ∼ 15 m. The observed characteristic flare shape is inconsistent with hot-spot orbits viewed edge-on. Individually modeling the light curves of the flares, we derived constraints on the inclination of the orbital plane of the hot spots with respect to the observer (i ∼ 30° , < 75°) and on the characteristic timescale of the intrinsic variability (a few tens of minutes).

The effect of NiTi rotary systems activated with different kinematics on canal transportation and centring ability. A concise review

One of the most crucial steps in endodontic therapy is canal preparation. The root canal should have a flare shape from apex to coronal areas, with the apical foramen maintained in its original relationship to the surrounding tissues and root surface. Anatomical complexity causes most endodontic problems. Ledges, zips, perforations, and root canal transportation are more probable in curved canals because all preparation procedures and instruments deviate the prepared canal away from its initial axis. The type of kinematics employed, including continuous rotation, reciprocation movement, and adaptive movement, as well as root canal anatomy and instrument design features, all have been found as factors that may affect canal transportation. There are controversial results concerning the influence of kinematic on canal transportation. These results may be attributed to a lack of standardisation in file characteristics such as taper, size, and cross-section. Studies started using the same system under continuous rotation and reciprocation movement or adaptive motion to overcome these issues. This article reviews the effects of movement types on canal transportation and centring ability when all other variables are the same.

Characteristics of flares on giant stars

Context. Although late-type dwarfs and giant stars are substantially different, their flares are thought to originate in similar physical processes and differ only by a scale factor in the energy levels. We study the validity of this approach. Aims. We search for characteristics of flares on active giants, which might be statistically different from those on main-sequence stars. Methods. We used nearly 4000 flares of 61 giants and 20 stars of other types that were observed with Kepler in long-cadence mode, which is the only suitable database for this comparative study. For every flare, we derived the duration and energy and gathered stellar parameters. Correlations between the flare characteristics and various stellar parameters were investigated. Results. Strong correlations are found between the flare duration and the surface gravity, luminosity, and radii of the stars. Scaled flare shapes appear to be similar on giants and dwarfs with a 30 min cadence. The logarithmic relation of flare energy and duration is steeper for stars with lower surface gravity. Observed flares are longer and more energetic on giants than on dwarfs on average. Conclusions. The generalized linear scaling for the logarithmic relation of flare energy and duration with a universal theoretical slope of ≈1/3 should slightly be modified by introducing a dependence on surface gravity.

Searching for Quasi-periodic Oscillations in Astrophysical Transients Using Gaussian Processes

Analyses of quasi-periodic oscillations (QPOs) are important to understanding the dynamic behavior in many astrophysical objects during transient events like gamma-ray bursts, solar flares, magnetar flares, and fast radio bursts. Astrophysicists often search for QPOs with frequency-domain methods such as (Lomb–Scargle) periodograms, which generally assume power-law models plus some excess around the QPO frequency. Time-series data can alternatively be investigated directly in the time domain using Gaussian process (GP) regression. While GP regression is computationally expensive in the general case, the properties of astrophysical data and models allow fast likelihood strategies. Heteroscedasticity and nonstationarity in data have been shown to cause bias in periodogram-based analyses. GPs can take account of these properties. Using GPs, we model QPOs as a stochastic process on top of a deterministic flare shape. Using Bayesian inference, we demonstrate how to infer GP hyperparameters and assign them physical meaning, such as the QPO frequency. We also perform model selection between QPOs and alternative models such as red noise and show that this can be used to reliably find QPOs. This method is easily applicable to a variety of different astrophysical data sets. We demonstrate the use of this method on a range of short transients: a gamma-ray burst, a magnetar flare, a magnetar giant flare, and simulated solar flare data.

Numerical and experimental evaluation of flue gas recirculation for syngas combustion

Biomass gasification can be an interesting solution for the energy production to fight global warming and the environment pollution. The flare apparatus is an essential component of gasification systems, but considering small scale ones, it is often quite simple and not very optimized. A way to minimize the NOx production during the combustion is recirculating the flue gas into the flames, making the combustion zone cold and inhibiting the nitrogen oxides formation. In this work different flare designs were numerically evaluated through OpenFOAM software to find the best flare shape that can guarantee the flue gas recirculation. Simulations results were verified building and testing a flare with an optimized geometry for a small-scale gasification system. Numerical simulation and experimental tests shown that it can be possible to design a simple flare for syngas combustion that guarantee low combustion temperature through flue gas recirculation.

A new approach to controlling metal transfer by dynamic modification in gas composition of arc atmosphere: studies on pulsed gas MAG welding*

ABSTRACT It has been well known that, in GMA welding, various welding phenomena are largely affected by the type of shielding gas used. However, up to the present time, almost no attempt has been made to utilize ‘gas composition’ for controlling welding phenomena. This study focused on this point and, thus, an investigation was made to understand how dynamic gas compositional modification affected various welding phenomena. In this study, pulsed Ar gas was injected periodically into CO2 shielding gas so that the gas composition of arc atmosphere largely modified in a very short period of time. It was found that this quick gas compositional change from CO2 to Ar led to a large decrease in arc voltage and an arc shape change from a constricted shape to a flare shape and that a molten droplet formed at the electrode tip during the CO2 period was released due to a sudden change in force balance between the molten droplet and the arc. The increase in current stimulated by the voltage drop may have assisted the metal drop detachment due to an increase in electromagnetic pinch force. If the cycle of this periodical Ar gas injection was selected to be shorter than that of repelled metal transfer in CO2 atmosphere, the repelled transfer was avoided and stable drop transfer occurred instead with far less spatter. Appropriate selections of the duration time of pulsed Ar gas injections avoided spray transfer which might cause undesirable finger-like penetration profiles. This new conceptual welding method, namely ‘Pulsed Gas MAG Welding’, required only a small amount of Ar gas to obtain the effects mentioned above.

A Survey of Performance Enhancement Techniques of Antipodal Vivaldi Antenna

The increasing proliferation of advanced devices for UWB, 5G communication, micrometer-wave, and millimeter-wave communication demands an antenna which can handle huge data rates, provides high gain and stable radiation pattern as a panacea of most of the current wireless communication problems. Many different antenna designs have been proposed by the researchers but, Antipodal Vivaldi Antenna (AVA) has drawn the attention of most of the researchers because of its high gain, wide bandwidth, less radiation loss, and stable radiation pattern. Different methods are presented to make AVA more compact while maintaining the performance of an antenna to an acceptable level. These different methods are substrate choice, flare shape, slots, and feeding connectors. Also, AVA performance can be enhanced by incorporating corrugation, dielectric lens, patch in between two flares of AVA, balanced AVA (BAVA), metamaterial, computational intelligence (CI), and AVA array. The AVA performance enhancement techniques modify the electrical and physical properties of an antenna which in turn improves its performance. A large number of performance enhancement methods of AVA design have been proposed, however, no comprehensive study exists to categorize these performance enhancement techniques and outline their concepts, advantages, disadvantages, and applications. So, in this paper, we have attempted to outline all methods available for enhancing and optimizing the parameters of AVA. Additionally, to validate some of the important performance enhancement methods, they are incorporated in the basic conventional AVA design and further simulation results are obtained for the same which are in line with the surveyed literature. Each method is explained in detail by incorporating its key points, merits, and demerits. Moreover, illustrations from the literature are given to demonstrate improvement in the parameters as a result of applying a particular performance enhancement technique.

Evolution over time of the Milky Way’s disc shape

Context. Galactic structure studies can be used as a path to constrain the scenario of formation and evolution of our Galaxy. The dependence with the age of stellar population parameters would be linked with the history of star formation and dynamical evolution. Aims. We aim to investigate the structures of the outer Galaxy, such as the scale length, disc truncation, warp and flare of the thin disc and study their dependence with age by using 2MASS data and a population synthesis model (the so-called Besançon Galaxy Model). Methods. We have used a genetic algorithm to adjust the parameters on the observed colour–magnitude diagrams at longitudes 80° ≤ ℓ ≤ 280° for | b | ≤ 5.5°. We explored parameter degeneracies and uncertainties. Results. We identify a clear dependence of the thin disc scale length, warp and flare shapes with age. The scale length is found to vary between 3.8 kpc for the youngest to about 2 kpc for the oldest. The warp shows a complex structure, clearly asymmetrical with a node angle changing with age from approximately 165° for old stars to 195° for young stars. The outer disc is also flaring with a scale height that varies by a factor of two between the solar neighbourhood and a Galactocentric distance of 12 kpc. Conclusions. We conclude that the thin disc scale length is in good agreement with the inside-out formation scenario and that the outer disc is not in dynamical equilibrium. The warp deformation with time may provide some clues to its origin.

Effect of ship bow overhang on water shipping for ship advancing in regular head waves

This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.

PHOTOMETRIC STUDY ON STELLAR MAGNETIC ACTIVITY. I. FLARE VARIABILITY OF RED DWARF STARS IN THE OPEN CLUSTER M37

Based on one-month long MMT time-series observations of the open cluster M37, we monitored light variations of nearly 2500 red dwarfs and successfully identified 420 flare events from 312 cluster M dwarf stars. For each flare light curve, we derived observational and physical parameters, such as flare shape, peak amplitude, duration, energy, and peak luminosity. We show that cool stars produce serendipitous flares energetic enough to be observed in the $r$-band, and their temporal and peak characteristics are almost the same as those in traditional $U$-band observations. We also found many large-amplitude flares with inferred $\Delta u > 6$ mag in the cluster sample which had been rarely reported in previous ground-based observations. Following the ergodic hypothesis, we investigate in detail statistical properties of flare parameters over a range of energy ($E_{r}$ $\simeq$ $10^{31}-10^{34}$ erg). As expected, there are no statistical differences in the distributions of flare timescales, energies, and frequencies among stars of the same age and mass group. We note that our sample tend to have longer rise and decay timescales compared to those seen in field flare stars of the same spectral type and be more energetic. Flare frequency distributions follow power-law distributions with slopes $\beta \sim0.62-1.21$ for all flare stars and $\beta \sim0.52-0.97$ for stars with membership information ($P_{mem} \geq 0.2$). These are in general agreement with previous works on flare statistics of young open clusters and nearby field stars. Our results give further support to the classical age-activity relations.

3D 어패럴 캐드 시스템으로 제작된 가상의복의 소재물성별 실물 재현도에 관한 연구

This research was conducted to provide basic data to improve expressivity required for virtual clothing to replace actual clothing. For the experiment, 6 materials were selected and 12(2 kinds of length) actual flared skirts were made. At the same time, simulations were carried out on OptiTex Runway 12.0 for 36(12 kinds of skirts <TEX>$\times$</TEX> KES, FTU, KES weight/10) kinds of virtual flared skirts, which were applied with the measured property values (thickness, weight, bending, shear, friction, and stretch). Also, the study compared and analyzed the wearing images, silhouette overlapping images, and skirt length measurements of the actual and virtual skirts put on a dummy. As a result, the actual skirts showed clear distinction for each material. In contrast, virtual 1 and 2 expressed fabric 3 in the most similar way, but could not recreate the uniform, soft, and natural flare shape of the actual skirts in general. Virtual 3 formed natural flares as those of the actual skirts, and expressed fabric 1, 5, and 6 in a similar way. However, virtual 3 had too much volume and barely showed any distinction for each material. All of virtual 1, 2, and 3 expressed different flare shapes on the front and back sides of the skirt similarly to the actual skirts, and had a good visual expression for the color and texture of the materials. However, they could not effectively express the elasticity and fabric sagging in the bias direction.

Interactions of higher order tip effects in critical dimension-AFM linewidth metrology

A major challenge in critical dimension atomic force microscope width metrology is accounting for the effects of the tip on the apparent features in an image. The overall effect of the tip is to broaden the apparent width of lines and narrow the apparent width of trenches as a result of the geometrical interaction of the tip with the surface. To a first approximation, this effect can be well-modeled as a constant bias in width measurements, independent of the specific feature characteristics, by the width of the tip. Beyond this approximation, there are a number of smaller tip effects related to the measurement details. Some of these result from the details and interactions of the tip shape and feature shape, resulting in small variations of the tip bias from feature to feature and measurement to measurement. These effects are sometimes called shape effects, secondary effects, or higher order tip effects. One source of higher order effects is due to the lateral dithering of the tip, which increases the effective tip width. However, in addition to this known effect, the tip dither may also affect the apparent edge heights of the tip flare. Although the apparent tip width is expected to depend on lateral dither, the apparent edge height, at least in principle, would not be expected to depend on lateral dither. Our analysis suggests that this apparent dependence results from the interaction of the fine details of the tip flare shape and the dither envelope with the specific algorithm used to estimate the edge height. Consequently, both the sign and the magnitude of the dependence are specific to every tip. This is one example of the inter-dependencies that can be present when evaluating higher-order tip effects. Although these are often small, accurate metrology in some applications may require consideration of possible interactions between such smaller, secondary tip effects. The authors illustrate this with examples from photomask metrology, where measurement of chrome features on binary masks requires some attention to secondary tip effects.

A simple alternative approach to assess the effect of the above-water bow form on the ship added resistance

In the paper, a simple alternative approach to assess the effect of the above-water bow form on the added resistance for the ship advancing in longitudinal waves is investigated. The strip theory and source distribution method are applied to solve the corresponding boundary conditions and analyze nonlinear motions and mean added resistance. In order to calculate the instantaneous ship motions and nonlinear forces with respect to the different draft, the time domain simulation technique based on the 4th Runge–Kutta method is applied here, and the instantaneous mean added resistance for a ship with different bow flare can be further obtained. The “total quasi-mean added resistance” is then defined to assess the virtual effect of the above-water bow flare shape. The present results show that the larger the bow flare, the larger the added resistance. The effect of wave profile along the ship length on the added resistance is also deeply investigated for discussions in the study.

X-ray variability patterns in blazars

We study the expected variability patterns of blazars within the two-zone acceleration model putting special emphasis on flare shapes and spectral lags. We solve semi-analytically the kinetic equations which describe the particle evolution in the acceleration and radiation zone. We then perturb the solutions by introducing Lorentzian variations in its key parameters and examine the flaring behavior of the system. We apply the above to the X-ray observations of blazar 1ES 1218+304 which exhibited a hard lag behavior during a flaring episode and discuss possibilities of producing it within the context of our model. The steady-state radio to X-rays emission of 1ES 1218+304 can be reproduced with parameters which lie well within the ones generally accepted from blazar modeling. Additionally, we find that the best way to explain its flaring behavior is by varying the rate of particles injected in the acceleration zone.

Numerical Prediction for the Size and Shape of a Flare in a Cross-Wind

UN MODELO DE DINAMICA DE FLUIDOS COMPUTACIONAL ES UTILIZADO PARA SIMULAR LA COMBUSTION TURBULENTA EN UN QUEMADOR ELEVADO DENTRO DE UN FLUJO CRUZADO DE AIRE. LA INVESTIGACION ESTA ENFOCADA, PRINCIPALMENTE, EN EL ESTUDIO DE LA INFLUENCIA DE LA VELOCIDAD DEL FLUJO CRUZADO EN PARAMETROS AERODINAMICOS DE LA LLAMA. LA SIMULACION DEL FLUJO ES TRIDIMENSIONAL Y EN COORDENADAS CARTESIANAS. PARA SIMULAR LA COMBUSTION ES USADO UN MODELO DE QUIMICA RAPIDA CON UN PASO DE REACCION IRREVERSIBLE PARA FORMAR CO2 Y H2O. UN MODELO DE RADIACION ES USADO PARA IDENTIFICAR LA TRAYECTORIA MEDIA DE LA LLAMA. LA CONFIGURACION SIMULADA CONSISTE EN UNA DESCARGA DE PROPANO EXPUESTA A UNA CORRIENTE DE AIRE, LA CUAL PROPORCIONA EL OXIGENO PARA QUE SE LLEVE A CABO LA COMBUSTION. LA VELOCIDAD DE ESTE FLUJO CRUZADO SE MODIFICA DESDE 0.8 M/S HASTA 12 M/S. COMPARACIONES CON DATOS EXPERIMENTALES MUESTRAN QUE LAS PREDICCIONES, EN TERMINOS DE LA LONGITUD DE LLAMA Y EL ANGULO DE DEFLEXION, SE PREDICEN ADECUADAMENTE.

The Influence of Morphological Changes in Amplatzer Device on the Atrial and Aortic Walls Following Transcatheter Closure of Atrial Septal Defects

This study prospectively investigated morphological changes in Amplatzer Septal Occluder (ASO) over time and the influences of these changes on the atrial and aortic walls after atrial septal defect (ASD) closure. Between August 2005 and December 2007, 78 patients with ASD were treated with ASO devices and changes in the device shape, the device thickness, and relations of the discs to the atrial and aortic walls over time were evaluated by transesophageal echocardiography immediately and 3-12 months after deployment. The maximum unstretched ASD diameter was 16.2 +/- 4.8 mm and the device diameter selected was 20.6 +/- 5.5 mm. At the time of last follow-up, the device thickness decreased by 17-33%, 6 of 26 devices with a flare shape on the aortic side developed a closed shape, and the relations of the discs to the anterior atrial and aortic walls changed from touching to intermittent compression in 14 of the 78 cases. In these 14 cases, the aortic rim was significantly smaller, the number of flared device shapes on the aortic side/the number of closed shapes immediately after deployment was significantly larger, and the maximum device thickness at the middle part was significantly more decreased than those in other cases. As the device becomes thinner, loses its flexibility, and often changes from a flare-to-closed shape on the aortic side over time, the edges of ASO can start to compress the atrial and aortic walls. However, erosion was not recognized in these cases.