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Accurate classification of celestial objects is essential for advancing our understanding of the universe. MargNet is a recently developed deep learning-based classifier applied to the Sloan Digital Sky Survey (SDSS) Data Release 16 (DR16) dataset to segregate stars, quasars, and compact galaxies using photometric data. MargNet utilizes a stacked architecture, combining a Convolutional Neural Network (CNN) for image modelling and an Artificial Neural Network (ANN) for modelling photometric parameters. Notably, MargNet focuses exclusively on compact galaxies and outperforms other methods in classifying compact galaxies from stars and quasars, even at fainter magnitudes. In this study, we propose enhancing MargNet's performance by incorporating attention mechanisms and Vision Transformer (ViT)-based models for processing image data. The attention mechanism allows the model to focus on relevant features and capture intricate patterns within images, effectively distinguishing between different classes of celestial objects. Additionally, we leverage ViTs, a transformer-based deep learning architecture renowned for exceptional performance in image classification tasks. We enhance the model's understanding of complex astronomical images by utilizing ViT's ability to capture global dependencies and contextual information. Our approach uses a curated dataset comprising 240,000 compact and 150,000 faint objects. The models learn classification directly from the data, minimizing human intervention. Furthermore, we explore ViT as a hybrid architecture that uses photometric features and images together as input to predict astronomical objects. Our results demonstrate that the proposed attention mechanism augmented CNN in MargNet marginally outperforms the traditional MargNet and the proposed ViT-based MargNet models. Additionally, the ViT-based hybrid model emerges as the most lightweight and easy-to-train model with classification accuracy similar to that of the best-performing attention-enhanced MargNet. This advancement in deep learning will contribute to greater success in identifying objects in upcoming surveys like the Vera C. Rubin Large Synoptic Survey Telescope. [ABSTRACT FROM AUTHOR]

High-noise astronomical-image denoising has always been a research hotspot in deep space exploration. Compressive sensing (CS) is an advanced technology used for high-dimensional signal processing. It is useful for processing high-resolution astronomical images. To obtain high-quality astronomical images, a CS spatially adaptive total variation iterative (CSSATVI) method is proposed herein. In this method, a curvelet transform based on an adaptive curvelet soft thresholding operator is proposed to adaptively remove hidden noise information in the process of image sparse representation, and a novel CS denoising reconstruction model proposed is used to deeply mine the texture, edge and other detailed information. Moreover, a novel reconstruction strategy is proposed for preserving detailed image information in the iterative reconstruction process to obtain high-quality astronomical images. Simulation results indicated that the proposed CSSATVI method can quickly reconstruct a high-quality astronomical image and preserve a large amount of astronomical image details; thus, it can be effectively applied in deep space exploration. [ABSTRACT FROM AUTHOR]

Clean energy is a major trend. The importance of photovoltaic power generation is also growing. Photovoltaic power generation is mainly affected by the weather. It is full of uncertainties. Previous work has relied chiefly on historical photovoltaics data for time series forecasts. However, unforeseen weather conditions can sometimes skew. Consequently, a spatial‐temporal‐meteorological‐long short‐term memory prediction model (STM‐LSTM) is proposed to compensate for the shortage of photovoltaic prediction models for uncertainties. This model can simultaneously process satellite image data, historical meteorological data, and historical power generation data. In this way, historical patterns and meteorological change information are extracted to improve the accuracy of photovoltaic prediction. STM‐LSTM processes raw satellite data to obtain cloud image data. It can extract cloud motion information using the dense optical flow method. First, the cloud images are processed to extract cloud position information. By adaptive attentive learning of images in different bands, a better representation for subsequent tasks can be obtained. Second, it is important to process historical meteorological data to learn meteorological change patterns. Last but not least, the historical photovoltaic power generation sequences are combined to obtain the final photovoltaic prediction results. After a series of experimental validation, the performance of the proposed STM‐LSTM model has a good improvement compared with the baseline model. [ABSTRACT FROM AUTHOR]

Due to the massive increase in astronomical images (such as James Web, Solar Dynamic Observatory, and Solar Orbiter), automatic image description is essential for solar and astronomical. Zernike moments (ZMs) are unique due to the orthogonality and completeness of Zernike polynomials (ZPs); hence, ZMs are valuable for converting a two-dimensional image to a one-dimensional series of complex numbers. The magnitude of ZMs is rotation invariant, and by applying image normalization, scale and translation invariants can be made, which are helpful properties for describing solar and astronomical images. The lower-order ZMs express the overall shape of the objects of an image, and the higher-order ZMs provide more details of the objects and delicate structures within an image. In this Python package, available at GitHub and PyPI, we describe the characteristics of ZMs via several examples of solar (large and small scale) features, astronomical, and human face images. These independent and unique properties of ZMs can describe the structure and morphology of objects in an image. Hence, ZMs are helpful in machine learning to identify and track the features of several. [ABSTRACT FROM AUTHOR]

One of the most valuable regions for telecommunication and space science is the geostationary earth orbit (GEO). On 27 November 2019, Egypt successfully launched its telecommunications satellite TIBA-1 into space. This paper aims to effectively identify and concurrently track this satellite from our Kottamia observatory station, National Research Institute of Astronomy and Geophysics (NRIAG) - Egypt. The images of the satellite are processed by the Apex II astronomical image processing package to obtain optical measurements, the apparent magnitude, and the phase angle. The initial orbit of the TIBA-1 satellite is determined using angle-only optical measurements for 4 months. The Double-r iteration method is used to determine the state distance vectors for orbital elements under different perturbation forces. Then, the results are compared with the positions predicted using the North American Aerospace Defense Command (NORAD) reference catalog. [ABSTRACT FROM AUTHOR]

The photometry of the binary star BX And (HIP 10027) is performed during several nights in October and November 2019, and October 2020 using B, V, and R Johnson-Cousins filters in Dr. Mojtahedi Observatory of the University of Birjand. Astronomical image processing and data reduction are performed by the IRIS software and light curves are obtained. These curves, along with the radial velocity data of the binary star, are analyzed by the Phoebe program to determine the physical and geometric parameters of the system. The evolutionary state of this system is investigated using the Hertzsprung-Russell (H-R) and density vs color index diagrams. The O-C curve is plotted using the eclipse times obtained in this study and those reported in the literature. By fitting a quadratic function to this curve, a new linear ephemeris is obtained for the system, and the mass transfer rate between the components of the system is determined. A periodic behavior is observed in the residuals, after subtracting the quadratic function from the O-C curve. These periodic changes are attributed to the presence of a third component in the system. The parameters of the third component are determined by fitting the light-time function to the residuals curve. [ABSTRACT FROM AUTHOR]

The present paper describes reduction procedures and imaging of radio astronomical data from the gravitational lens system CLASS B0631+519 acquired by e-MERLIN interferometer. The source has been previously imaged with VLA, MERLIN and the VLBA interferometers. Data reduction and polarisation calibration procedures will provide data on Faraday effects such as Faraday rotation and depolarization between lensed images that in turn carry information on large and small-scale magnetic fields in the lensing galaxy. Reduction of data and imaging of the radio astronomical source have been achieved using Astronomical Image Processing System (AIPS) in conjunction with automatic data reduction pipelines that performed specific data processing steps. As a result, the sky map for the gravitational lens system has been successfully acquired and accuracy comparing the generated map to sky maps of the source produced by different authors has been confirmed. [ABSTRACT FROM AUTHOR]

This paper presents a new type of north finding sensor. The passive optical sensor captures images of the sky at a high frame rate and analyzes them into a polarized map of the sky with a high degree of accuracy. The sensor operates in real time, under various weather and atmospheric conditions. The sensor output shows high heading accuracy relative to the celestial true north. Based upon the NAS-14V2 astronomical method of navigation, it is possible to define the sensor global position on earth. [ABSTRACT FROM AUTHOR]

We develop a technique to quantitatively characterize the high-energy electron environment using the Galileo spacecraft solid-state imaging (SSI) instrument and results from 3-D Monte Carlo particle transport simulations in Geant4, validating our findings with the Galileo energetic particle detector (EPD). We postprocess raw SSI images to obtain frames with only the radiation contribution. The camera settings (gain state, filter, and so on) are used to compute the intensity of the observed radiation hits. Simulating the response of the SSI instrument to mono-energetic electron environments, we find that the SSI is capable of detecting ≥10-MeV electrons (>90% of <10-MeV particles are stopped with 95% confidence). Using geometric factors computed for the SSI, we calculate the environment particle flux given a number of pixels with radiation hits. We compare the SSI results to measurements from the Galileo EPD, examining the electron fluxes from the EPD >11-MeV integral flux channel. We find agreement within $3\sigma $ of the EPD data for 43 out of 43 (100%) of the SSI images evaluated. 62% of fluxes are also within $1\sigma $ of the EPD data. This approach can be applied to other sets of imaging data (star trackers) in energetic electron environments, such as those found in geostationary Earth orbit. [ABSTRACT FROM AUTHOR]

The article reports that Atacama Large Millimeter Array, world's biggest radio telescope array, is getting hardware and software upgrades including data transmission, replacing the correlator, and installing new detectors to gain a clearer view of objects from the Solar System.

This paper proposes three different distribution strategies for very large 3D image deconvolution algorithms. The deconvolution problem is generic and tailored for spatio-spectral 3D image reconstruction. The three proposed algorithms for large-scale data are distributed in the sense that both the storage and the computations are distributed over several compute nodes. As a result, the workload is drastically reduced compared to a centralized approach where the storage and the computations are handled by a single compute node. The proposed algorithms are validated through experiments on simulated astronomical images. [ABSTRACT FROM AUTHOR]

Context. A low-mass brown dwarf has recently been imaged around HR 2562 (HD 50571), a star hosting a debris disk resolved in the far infrared. Interestingly, the companion location is compatible with an orbit coplanar with the disk and interior to the debris belt. This feature makes the system a valuable laboratory to analyze the formation of substellar companions in a circumstellar disk and potential disk-companion dynamical interactions. Aims. We aim to further characterize the orbital motion of HR 2562 B and its interactions with the host star debris disk. Methods. We performed a monitoring of the system over ~10 months in 2016 and 2017 with the VLT/SPHERE exoplanet imager. Results. We confirm that the companion is comoving with the star and detect for the first time an orbital motion at high significance, with a current orbital motion projected in the plane of the sky of 25 mas (~0.85 au) per year. No orbital curvature is seen in the measurements. An orbital fit of the SPHERE and literature astrometry of the companion without priors on the orbital plane clearly indicates that its orbit is (quasi-)coplanar with the disk. To further constrain the other orbital parameters, we used empirical laws for a companion chaotic zone validated by N-body simulations to test the orbital solutions that are compatible with the estimated disk cavity size. Non-zero eccentricities (>0.15) are allowed for orbital periods shorter than 100 yr, while only moderate eccentricities up to ~0.3 for orbital periods longer than 200 yr are compatible with the disk observations. A comparison of synthetic Herschel images to the real data does not allow us to constrain the upper eccentricity of the companion. [ABSTRACT FROM AUTHOR]

Aims. Compressed sensing realized by means of regularized deconvolution and the finite isotropic wavelet transform is effective and reliable in hard X-ray solar imaging. Methods. The method uses the finite isotropic wavelet transform with the Meyer function as the mother wavelet. Furthermore, compressed sensing is realized by optimizing a sparsity-promoting regularized objective function by means of the fast iterative shrinkage-thresholding algorithm. Eventually, the regularization parameter is selected by means of the Miller criterion. Results. The method is applied against both synthetic data mimicking measurements made with the Spectrometer/Telescope Imaging X-rays (STIX) and experimental observations provided by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The performances of the method are qualitatively validated by comparing some morphological properties of the reconstructed sources with those of the corresponding synthetic configurations. Furthermore, the results concerning experimental data are compared with those obtained by applying other visibility-based reconstruction methods. Conclusions. The results show that when the new method is applied to synthetic STIX visibility sets, it provides reconstructions with a spatial accuracy comparable to the accuracy provided by the most popular method in hard X-ray solar imaging and with a higher spatial resolution. Furthermore, when it is applied to experimental RHESSI data, the reconstructions are characterized by reliable photometry and by a notable reduction of the ringing effects caused by the instrument point spread function. [ABSTRACT FROM AUTHOR]

Context. Angular differential imaging (ADI) takes advantage of the field rotation naturally induced by altitude-azimuth mounts to reduce static speckle noise. Used with facilities like SPHERE at the VLT, this technique allows one to achieve contrast ratios of 10􀀀6. The ADI method, however, intrinsically limits the useful exposure time on a given target (to about 1–2 h per night). Detecting fainter exoplanets requires the combination of multiple observations acquired on different nights, potentially spread over several weeks or months, but the unknown orbital motion of the planet makes it particularly dififcult to properly combine all observations. In the near future, with the upcoming generation of Extremely Large Telescopes (ELTs) with increased resolution, the orbital motion may even become a problem on a single night. Aims. We present a proof of concept for a new algorithm which can be used to detect exoplanets in high-contrast images. The algorithm properly combines multiple observations acquired during different nights, taking into account the orbital motion of the planet. Methods. We simulate SPHERE/IRDIS time series of observations in which we blindly inject planets on random orbits, at random levels of signal-to-noise ratio (S/N), below the detection limit (down to S=N ' 1:5). We then use an optimization algorithm to “guess” the orbital parameters, and take into account the orbital motion to properly recombine the different images and eventually detect the planets. Results. We show that an optimization algorithm can indeed be used to find undetected planets in temporal sequences of images, even if they are spread over orbital time scales. As expected, the typical gain in S/N is p n, n being the number of observations combined. We find that the K-Stacker algorithm is able de-orbit and combine the images to reach a level of performance similar to what could be expected if the planet was not moving.We find recovery rates of '50% at S=N = 5.We also find that the algorithm is able to determine the position of the planet in individual frames at one pixel precision, even despite the fact that the planet itself is below the detection limit in each frame. Conclusions. Our simulations show that K-Stacker can be used to detect planets at very low S/N level, down to '2 in individual frames, for series of ten images. This could be used to increase the contrast limit of current exoplanet imaging instruments and to discover fainter bodies. We also suggest that the ability of K-Stacker to determine the position of the planet in every image of the time series could be used as part of a new observing strategy in which long exposures would be broken into shorter ones spread over months. This could make it possible to determine the orbital parameters of a planet without multiple high-S/N (>5) detections. [ABSTRACT FROM AUTHOR]

Compressive sensing promises to enable bandwidth-efficient on-board compression of astronomical data by lifting the encoding complexity from the source to the receiver. The signal is recovered off-line, exploiting graphical processing unit (GPU)’s parallel computation capabilities to speedup the reconstruction process. However, inherent GPU hardware constraints limit the size of the recoverable signal and the speedup practically achievable. In this work, we design parallel algorithms that exploit the properties of circulant matrices for efficient GPU-accelerated sparse signals recovery. Our approach reduces the memory requirements, allowing us to recover very large signals with limited memory. In addition, it achieves a 10-fold signal recovery speedup, thanks to ad-hoc parallelization of matrix–vector multiplications and matrix inversions. Finally, we practically demonstrate our algorithms in a typical application of circulant matrices: deblurring a sparse astronomical image in the compressed domain. [ABSTRACT FROM PUBLISHER]

We address the problem of automatically coregistering planetary images to a common baseline, introducing a novel generic technique that achieves an unprecedented robustness to different image inputs, thus making batch-mode coregistration achievable without requiring the usual parameter tweaking. We introduce a novel image matching technique, which boosts matching performance even under the most strenuous circumstances, and experimentally demonstrate validation through an extensive experimental multi-instrument setup that includes images from eight high-resolution data sets of the Mars and the Moon. The technique is further tested in a batch-mode processing, in which approximately 1.6% of all high-resolution Martian imagery is coregistered to a common baseline. [ABSTRACT FROM AUTHOR]

Unlike most web-based citizen science programmes, RAD@home citizen scientists are trained in an interactive manner, both online and in person. This Collaboratory model can alleviate various geo-political and socio-economic constraints on the growth of people in underdeveloped regions which is in synergy with mandates of the IAU Office of Astronomy for Development. Owing to its Inter-University collaboratory design, supported by over 30 research institutions, it can attempt to convert the 'Big Data Problem' into a 'Big Data Prospect' by direct training and involving citizens in discoveries from multi-telescope data. Using the RAD-RGB-maker web-tool, e-astronomers learn the basics of multi-wavelength (UV-optical-IR-radio) extragalactic astronomy and create preliminary discovery reports of unusual radio sources thus becoming Co-Investigator in follow-up observations and publications (e.g. Discovery of RAD12). International expansion of RAD@home has been initiated during the recent IAU symposium 375 through its Educational and Outreach programme. [ABSTRACT FROM AUTHOR]

The RAD@home RGB-maker Tool is a python-based web application that enables citizen science research through collaboration using open-source technology. The tool fetches FITS image data from NASA SkyView and generates false colour images in Red-Green-Blue channels with contour. This helps in the basic multi-wavelength understanding and characterization of extragalactic objects, and further analysis along with reporting of potential new discoveries in a uniform format. Students from Universities or science-graduate citizens gain skills in RGB-C image analysis and identify unique features in objects via either one-day online-weekend events or week-long in-person training. Trained citizen scientists in turn are part of rare discoveries such as the jet-galaxy interaction system RAD12. The tool has been successfully used by thousands of citizen scientists in India since its launch on 26 th January 2021 and has demonstrated the potential during IAU symposium 375 to be part of citizen science efforts with international participants. [ABSTRACT FROM AUTHOR]

We report an imaging capability of the Japan-led X-ray observatory Hitomi, formerly known as ASTRO-H. It carries four scientific instruments of Soft X-ray Imager (SXI: CCD camera), Hard X-ray Imager (HXI), Soft X-ray Spectrometer, and Soft Gamma-ray Detector, allowing us to perform a wide-band high-sensitive imaging spectroscopy. We highlight the specification and the performance we obtained with primarily regard to X-ray and soft gamma-ray imaging. Primary imaging instrument SXI utilizes four large-area X-ray CCDs positioned at the focal plane of Soft X-ray Telescope (SXT-I). Imaging area with a size of 62 mm square makes a largest field of view (FoV) of 38′ square among the focal plane X-ray detectors, which enables us to observe extended objects such as clusters of galaxies and galactic supernova remnants with a single pointing in the soft X-ray band from 0.4 to 12 keV. HXI employs the hybrid sensors consisting of four layers of double-sided silicon strip detectors and a single layer of cadmium telluride double-sided strip detector covering the energy band from 5 to 80 keV. After the successful launch of Hitomi on February 17th, 2016 and the subsequent start up of all the instruments, imaging performance of both imagers are verified as expected from the ground calibration tests. The position of the active galactic nucleus of the central galaxy NGC1275 in the Perseus cluster is precisely seen by SXI, while the positional difference of line-of-sight velocity dispersion of the hot intracluster medium is measured inside by SXS. From the observation of Crab nebula, we obtain the on-pulse hard X-ray image with HXI as well as the time-averaged image in which the torus of the pulsar wind nebula can be seen. [ABSTRACT FROM AUTHOR]

In beating cardiomyocytes, synchronized localized Ca2+ transients from thousands of active excitation-contraction coupling sites (ECC couplons) comprising plasma and sarcoplasmic reticulum membrane calcium channels are important determinants of the heart's performance. Nevertheless, our knowledge about the properties of ECC couplons is limited by the lack of appropriate experimental and analysis strategies. We designed CaCLEAN to untangle the fundamental characteristics of ECC couplons by combining the astronomer's CLEAN algorithm with known properties of calcium diffusion. CaCLEAN empowers the investigation of fundamental properties of ECC couplons in beating cardiomyocytes without pharmacological interventions. Upon examining individual ECC couplons at the nanoscopic level, we reveal their roles in the negative amplitude-frequency relationship and in b-adrenergic stimulation, including decreasing and increasing firing reliability, respectively. CaCLEAN combined with 3D confocal imaging of beating cardiomyocytes provides a functional 3D map of active ECC couplons (on average, 17,000 per myocyte). CaCLEAN will further enlighten the ECC-couplon-remodelling processes that underlie cardiac diseases. [ABSTRACT FROM AUTHOR]

Despite the popularity of the Graphics Processing Unit (GPU) for general purpose computing, one should not forget about the practicality of the GPU for fast scientific visualization. As astronomers have increasing access to three-dimensional (3D) data from instruments and facilities like integral field units and radio interferometers, visualization techniques such as volume rendering offer means to quickly explore spectral cubes as a whole. As most 3D visualization techniques have been developed in fields of research like medical imaging and fluid dynamics, many transfer functions are not optimal for astronomical data. We demonstrate how transfer functions and graphics shaders can be exploited to provide new astronomy-specific explorative colouring methods. We present 12 shaders, including four novel transfer functions specifically designed to produce intuitive and informative 3D visualizations of spectral cube data. We compare their utility to classic colour mapping. The remaining shaders highlight how common computation like filtering, smoothing and line ratio algorithms can be integrated as part of the graphics pipeline. We discuss how this can be achieved by utilizing the parallelism of modern GPUs along with a shading language, letting astronomers apply these new techniques at interactive frame rates. All shaders investigated in this work are included in the open source software SHWIRL (Vohl 2017). [ABSTRACT FROM AUTHOR]

The circum-galactic medium consists in gas orbiting around galaxies, whose faintness prevents any complete and easy detection. A powerful tool to detect such pattern can be found in using hyperspectral imaging. Nevertheless, detection in hyperspectral datacubes faces various problems, including well-fitted signal and noise descriptions to ensure further discrimination. A specificity of astronomical images resides in dealing with faint and very noisy signals. In this paper, we introduce a new constrained generalized likelihood ratio test adapted to the problem and a compound test to exploit most of the available information. We also investigate the use of both spatial information and multiple observations on a single scene, to enhance robustness. Numerical experiments on synthetic data are performed to quantify the gain of the different approaches. Finally, results on real hyperspectral astronomical data are presented, which may map for the first time observation of the circum-galactic medium around faint and distant galaxies. [ABSTRACT FROM AUTHOR]

The Dawn spacecraft Framing Camera (FC) acquired over 31,300 clear filter images of Ceres with a resolution of about 35 m/pxl during the eleven cycles in the Low Altitude Mapping Orbit (LAMO) phase between December 16 2015 and August 8 2016. We ortho-rectified the images from the first four cycles and produced a global, high-resolution, uncontrolled photomosaic of Ceres. This global mosaic is the basis for a high-resolution Ceres atlas that consists of 62 tiles mapped at a scale of 1:250,000. The nomenclature used in this atlas was proposed by the Dawn team and was approved by the International Astronomical Union (IAU). The full atlas is available to the public through the Dawn Geographical Information System (GIS) web page [ http://dawngis.dlr.de/atlas ] and will become available through the NASA Planetary Data System (PDS) ( http://pdssbn.astro.umd.edu/ ). [ABSTRACT FROM AUTHOR]

Mars Colour Camera on-board the Mars Orbital Mission makes use of a Bayer pattern detector. Spectral response of RGB (red, green and blue) pixels of Bayer detector shows large overlap which reduces the spectral information content of the image. In the present paper, a simple method is suggested to correct the data for spectral overlap. It is shown that correction process significantly increases the spectral information content of the image and enhances the ability of the sensor to identify different target types like dust clouds and water ice clouds. [ABSTRACT FROM AUTHOR]

We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour-composite images. Images in GZH were selected from various publicly released Hubble Space Telescope legacy programmes conducted with the Advanced Camera for Surveys, with filters that probe the rest-frame optical emission from galaxies out to z ~ 1. The bulk of the sample is selected to have mI814W < 23.5, but goes as faint as mI814W < 26.8 for deep images combined over five epochs. The median redshift of the combined samples is (z) = 0.9 ± 0.6, with a tail extending out to z ~ 4. The GZH morphological data include measurements of both bulge- and disc-dominated galaxies, details on spiral disc structure that relate to the Hubble type, bar identification, and numerous measurements of clump identification and geometry. This paper also describes a new method for calibrating morphologies for galaxies of different luminosities and at different redshifts by using artificially redshifted galaxy images as a baseline. The GZH catalogue contains both raw and calibrated morphological vote fractions for 119 849 galaxies, providing the largest data set to date suitable for large-scale studies of galaxy evolution out to z ~ 1. [ABSTRACT FROM AUTHOR]

Supernova (SN) 2015bh (or SNhunt275) was discovered in NGC 2770 on 2015 February with an absolute magnitude of Mr ~ -13.4 mag, and was initially classified as an SN impostor. Here, we present the photometric and spectroscopic evolution of SN 2015bh from discovery to late phases (~1 yr after). In addition, we inspect archival images of the host galaxy up to ~21 yr before discovery, finding a burst ~1 yr before discovery, and further signatures of stellar instability until late 2014. Later on, the luminosity of the transient slowly increases, and a broad light-curve peak is reached after about three months. We propose that the transient discovered in early 2015 could be a core-collapse SN explosion. The pre-SN luminosity variability history, the long-lasting rise and faintness first light-curve peak suggests that the progenitor was a very massive, unstable and blue star, which exploded as a faint SN because of severe fallback of material. Later on, the object experiences a sudden brightening of 3 mag, which results from the interaction of the SN ejecta with circumstellar material formed through repeated past mass-loss events. Spectroscopic signatures of interaction are however visible at all epochs. A similar chain of events was previously proposed for the similar interacting SN 2009ip. [ABSTRACT FROM AUTHOR]

We report the analysis of 22 B-band light curves of the dwarf nova V4140 Sgr obtained with SOAR Optical Imager (SOI)/SOAR during two nights along the decline of a superoutburst in 2006 September 12-24 and in quiescence over 50 d following the superoutburst. 3D eclipse mapping of the outburst light curves indicates that the accretion disc is elliptical (eccentricity e = 0.13) and that superhump maximum occurs when the mass donor star is aligned with the bulge of the elliptical disc. The accretion disc is geometrically thin both in outburst and in quiescence; it fills the primary Roche lobe in the outburst and shrinks to about half this size in quiescence. The stability of the eclipse shape, width and depth along quiescence and the derived disc surface brightness distribution indicate that the quiescent accretion disc is in a high-viscosity, steady-state. Flickering mapping of the quiescent data reveals that the lowfrequency flickering arises from an azimuthally extended stream-disc impact region at disc rim and from the innermost disc region, whereas the high-frequency flickering originates in the accretion disc. Assuming the disc-related flickering to be caused by fluctuations in the energy dissipation rate induced by magnetohydrodynamic turbulence (Geertsema & Achterberg), we find that the quiescent disc viscosity parameter is large, α ~ 0.2-0.4, at all radii. The highviscosity quiescent disc and the inferred lowdisc temperatures in superoutburst are inconsistent with expectations of the disc-instability model, and lead to the conclusion that the outbursts of V4140 Sgr are powered by mass transfer bursts from its donor star. [ABSTRACT FROM AUTHOR]

We are pursuing a project to build a database of phase calibration sources suitable for Giant Metrewave Radio Telescope (GMRT). Here we present the first release of 45 low frequency calibration sources at 235 MHz and 610 MHz. These calibration sources are broadly divided into quasars, radio galaxies and unidentified sources. We provide their flux densities, models for calibration sources, ( u, v) plots, final deconvolved restored maps and clean-component lists/files for use in the Astronomical Image Processing System ( aips) and the Common Astronomy Software Applications ( casa). We also assign a quality factor to each of the calibration sources. These data products are made available online through the GMRT observatory website. In addition we find that (i) these 45 low frequency calibration sources are uniformly distributed in the sky and future efforts to increase the size of the database should populate the sky further, (ii) spectra of these calibration sources are about equally divided between straight, curved and complex shapes, (iii) quasars tend to exhibit flatter radio spectra as compared to the radio galaxies or the unidentified sources, (iv) quasars are also known to be radio variable and hence possibly show complex spectra more frequently, and (v) radio galaxies tend to have steeper spectra, which are possibly due to the large redshifts of distant galaxies causing the shift of spectrum to lower frequencies. [ABSTRACT FROM AUTHOR]

The article discusses misconceptions on resolution, camera pixel count, interpolation and their effect on astronomical images, confusions between image sharpness and resolution and examination of pixel count as not a guarantee of image sharpness or high resolution. These include image sharpness as an indication of a well-balanced data in the spatial-frequency domain no matter the size of the image while resolution is a measure of how many pixels cover a given detail in an image.

Ground level enhancements (GLEs) of cosmic-ray intensity occur, on average, once a year. Because they are rare, studying the solar sources of GLEs is especially important to approach understanding their origin. The SOL2001-12-26 eruptive-flare event responsible for GLE63 seems to be challenging in some aspects. Deficient observations limited our understanding of it. Analysis of additional observations found for this event provided new results that shed light on the flare configuration and evolution. This article addresses the observations of this flare with the Siberian Solar Radio Telescope (SSRT). Taking advantage of its instrumental characteristics, we analyze the detailed SSRT observations of a major long-duration flare at 5.7 GHz without cleaning the images. The analysis confirms that the source of GLE63 was associated with an event in active region 9742 that comprised two flares. The first flare (04:30 - 05:03 UT) reached a GOES importance of about M1.6. Two microwave sources were observed, whose brightness temperatures at 5.7 GHz exceeded 10 MK. The main flare, up to an importance of M7.1, started at 05:04 UT and occurred in strong magnetic fields. The observed microwave sources reached a brightness temperature of about 250 MK. They were not static. After appearing on the weaker-field periphery of the active region, the microwave sources moved toward each other nearly along the magnetic neutral line, approaching the stronger-field core of the active region, and then moved away from the neutral line like expanding ribbons. These motions rule out an association of the non-thermal microwave sources with a single flaring loop. [ABSTRACT FROM AUTHOR]

A high resolution image showing fine structures is crucial for understanding the nature of solar prominence. In this paper, high resolution imaging of solar prominence on the New Vacuum Solar Telescope (NVST) is introduced, using speckle masking. Each step of the data reduction especially the image alignment is discussed. Accurate alignment of all frames and the non-isoplanatic calibration of each image are the keys for a successful reconstruction. Reconstructed high resolution images from NVST also indicate that under normal seeing condition, it is feasible to carry out high resolution observations of solar prominence by a ground-based solar telescope, even in the absence of adaptive optics. [ABSTRACT FROM AUTHOR]

An application of active contours without edges is presented as an efficient and effective means of extracting and characterizing coronal holes. Coronal holes are regions of low-density plasma on the Sun with open magnetic field lines. The detection and characterization of these regions is important for testing theories of their formation and evolution, and also from a space weather perspective because they are the source of the fast solar wind. Coronal holes are detected in full-disk extreme ultraviolet (EUV) images of the corona obtained with the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA). The proposed method detects coronal boundaries without determining any fixed intensity value in the data. Instead, the active contour segmentation employs an energy-minimization in which coronal holes are assumed to have more homogeneous intensities than the surrounding active regions and quiet Sun. The segmented coronal holes tend to correspond to unipolar magnetic regions, are consistent with concurrent solar wind observations, and qualitatively match the coronal holes segmented by other methods. The means to identify a coronal hole without specifying a final intensity threshold may allow this algorithm to be more robust across multiple datasets, regardless of data type, resolution, and quality. [ABSTRACT FROM AUTHOR]

We present the new Very Large Array 22 GHz and extended Multi-Element Remote-Linked Interferometer Network 5 GHz observations of CLASS B1030+074, a two-image strong gravitational lens system whose background source is a compact flat-spectrum radio quasar. In such systems we expect a third image of the background source to form close to the centre of the lensing galaxy. The existence and brightness of such images is important for investigation of the central mass distributions of lensing galaxies, but only one secure detection has been made so far in a galaxy-scale lens system. The noise levels achieved in our new B1030+074 images reach 3 μJy beam-1 and represent an improvement in central image constraints of nearly an order of magnitude over previous work, with correspondingly better resulting limits on the shape of the central mass profile of the lensing galaxy. Simple models with an isothermal outer power-lawslope nowrequire either the influence of a central supermassive black hole (SMBH), or an inner power-law slope very close to isothermal, in order to suppress the central image below our detection limit. Using the central mass profiles inferred from light distributions in Virgo galaxies, moved to z = 0.5, and matching to the observed Einstein radius, we now find that 45 per cent of such mass profiles should give observable central images, 10 per cent should give central images with a flux density still below our limit, and the remaining systems have extreme demagnification produced by the central SMBH. Further observations of similar objects will therefore allow proper statistical constraints to be placed on the central properties of elliptical galaxies at high redshift. [ABSTRACT FROM AUTHOR]

We introduce a new algorithm for colour separation and deblending of multi-band astronomical images called MuSCADeT which is based on Morpho-spectral Component Analysis of multi-band images. The MuSCADeT algorithm takes advantage of the sparsity of astronomical objects in morphological dictionaries such as wavelets and their differences in spectral energy distribution (SED) across multi-band observations. This allows us to devise a model independent and automated approach to separate objects with different colours. We show with simulations that we are able to separate highly blended objects and that our algorithm is robust against SED variations of objects across the field of view. To confront our algorithm with real data, we use HST images of the strong lensing galaxy cluster MACS J1149+2223 and we show that MuSCADeT performs better than traditional profile-fitting techniques in deblending the foreground lensing galaxies from background lensed galaxies. Although the main driver for our work is the deblending of strong gravitational lenses, our method is fit to be used for any purpose related to deblending of objects in astronomical images. An example of such an application is the separation of the red and blue stellar populations of a spiral galaxy in the galaxy cluster Abell 2744. We provide a python package along with all simulations and routines used in this paper to contribute to reproducible research efforts. [ABSTRACT FROM AUTHOR]

The moon is the brightest celestial body in the night sky, and it is of some value when determining the astronomical azimuth on a cloudy or foggy night or in a light-polluted city when there is no visible star. Based on the edge observations of the apparent moon using a total station, a global positioning system (GPS) receiver, a portable computer, and some appropriate software and instrumentation, an innovative method for determining the center of the apparent moon, is discussed in this paper, and calculation formulas are deduced in detail. Second, errors in the astronomical azimuth determination are quantitatively analyzed. Finally, two practical tests are performed in the central plains of China, and the results indicate that the difference between azimuth determination by Polaris and the moon is up to 700 from twofield tests. [ABSTRACT FROM AUTHOR]

Planetary rover exploration missions require accurate and computationally efficient robot localization in order to perform complex and cooperative tasks. The global localization on planetary environments can be competently addressed by incorporating orbital and ground rover imagery. An indicative approach could include (1) the extraction of regions of interest (ROIs) in orbital images, (2) the extraction of ROIs in rover images, (3) the ROI matching, and (4) the localization. In order to perform adequately in ROI matching, a model should be able to detect common ROIs. The work in hand tackles the problem of extracting such regions of interest that are observable on both orbital and rover images. The dedicated model that was designed and implemented contains a detection and a classification part. The detection of the ROIs is based on both their texture and their geometrical properties. Classification was performed on the result of the detection in order to annotate the ROIs and discard any outliers caused by false detection. The results prove that the model is able to detect commonly observable regions and, therefore, is considered to be an adequate preprocessing step in the context of a global rover localization system. [ABSTRACT FROM AUTHOR]

The Rosetta mission is a milestone in terms of science and public outreach. The European Space Agency and the Deutsches Zentrum für Luft- und Raumfahrt in particular did a marvellous job of sparking global public interest, driven by various events throughout the mission. In contrast, the actions of the Max Planck Society research group in charge of the high resolution Optical, Spectroscopic, and Infrared Remote Imaging System 1 were, in my opinion, the cause of some concern and bring to light an important debate in the relationship between outreach and science. This article seeks to review the outreach that surrounded the Rosetta mission and to highlight both the best practice that made it a success and the bad practice that set some aspects behind.2 [ABSTRACT FROM AUTHOR]

We address the problem of deconvolution of astronomical images that could be obtained with future large interferometers in space. The presentation is made in two complementary parts. The first part gives an introduction to the image deconvolution with linear and nonlinear algorithms. The emphasis is made on nonlinear iterative algorithms that verify the constraints of non-negativity and constant flux. The Richardson-Lucy algorithm appears there as a special case for photon counting conditions. More generally, the algorithm published recently by Lanteri et al. (2015) is based on scale invariant divergences without assumption on the statistic model of the data. The two proposed algorithms are interior-point algorithms, the latter being more efficient in terms of speed of calculation. These algorithms are applied to the deconvolution of simulated images corresponding to an interferometric system of 16 diluted telescopes in space. Two non-redundant configurations, one disposed around a circle and the other on an hexagonal lattice, are compared for their effectiveness on a simple astronomical object. The comparison is made in the direct and Fourier spaces. Raw "dirty" images have many artifacts due to replicas of the original object. Linear methods cannot remove these replicas while iterative methods clearly show their efficacy in these examples. [ABSTRACT FROM AUTHOR]

Critical crescent moon detection is a new subject in astronomical image processing. Astronomers take photos with valuable astronomical calculations using CCD cameras and telescopes. Crescent moon might not be visible in such photos, so they must be enhanced. For this purpose, we apply common image processing methods on crescent moon images such as power operator, gamma transformation, global and local histogram equalization, POSHE, CLAHE, local enhancement, gain/offset correction, homomorphic filtering, SSR, MSR, MSRCR, wavelet and curvelet transformations. Second, we use our new methods like PB, POSP, HShistV , CurvHShistV and local brightness intensity enhancement to detect the crescent. Then we evaluate and compare the outputs of these algorithms by standard subjective evaluation tests. Finally, we conclude that these methods can give us enhanced images in which the crescent moon can be seen by human observers. We introduce our new toolbox which is named CMD, a standalone tool developed in Matlab for Critical Crescent Moon Detection using the above techniques. [ABSTRACT FROM AUTHOR]

Detection and localization of astronomical objects are two of the most fundamental topics in astronomical science where localization uses detection results. Object localization is based on modeling of point spread function and estimation of its parameters. Commonly used models as Gauss or Moffat in objects localization provide good approximation of analyzed objects but cannot be sufficient in the case of exact applications such as object energy estimation. Thus the use of sophisticated models is upon the place. One of the key roles plays also the way of the objective function estimation. The least square method is often used, but it expects data with normal distribution, thus there is a question of a maximum likelihood method application. Another important factor of presented problem is choice of the right optimization method. Classical methods for objective function minimization usually require a good initial estimate for all parameters and differentiation of the objective function with respect to model parameters. The results indicated that stochastic methods such as simulated annealing or harmony search achieved better results than the classical optimization methods. [ABSTRACT FROM AUTHOR]

A new profile recovery method which is called time–frequency peak filtering (TFPF) is introduced to low signal-to-noise ratio (SNR) astronomical fiber spectral signals. TFPF is an effective noise removal method, which is essentially instantaneous frequency (IF) estimation based on Wigner–Ville distribution (WVD). To achieve a better noise suppression result of spectral signal, we propose an improved TFPF, which combines the pseudo WVD (PWVD) and the smoothed pseudo WVD (SPWVD). The proposed method produces a data fusion from the outcomes of PWVD and SPWVD to sharpen the time–frequency distribution and adopts a sine function to eliminate interference points in time–frequency domain. We test our method on both simulated and observed data based on the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) project. The results show good performance of the proposed method. [ABSTRACT FROM AUTHOR]