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Stellar activity cycles reveal continuous relaxation and induction of magnetic fields. The activity cycle is typically traced through the observation of cyclic variations in total brightness or Ca H&K emission flux of stars, as well as cyclic variations in the orbital periods of binary systems. In this work, we report the identification of a semidetached binary system (TIC 16320250) consisting of a white dwarf (0.67 M _⊙ ) and an active M dwarf (0.56 M _⊙ ). The long-term multiband optical light curves spanning twenty years revealed three repeated patterns, suggestive of a possible activity cycle of about 10 years of the M dwarf. Light-curve fitting indicates the repeated variation is caused by the evolution, particularly the motion, of polar spots. The significant Ca H&K, H α , ultra-violet, and X-ray emissions imply that the M dwarf is one of the most magnetically active stars. We propose that in the era of large time-domain photometric sky surveys (e.g., ASAS-SN, Zwicky Transient Facility, LSST, Sitian), long-term light-curve modeling can be a valuable tool for tracing and revealing stellar activity cycle, especially for stars in binary systems.

Stellar coronal mass ejections (CMEs) have recently attracted much attention for their impacts on stellar evolution and surrounding exoplanets. RS CVn-type stars could produce large flares, and therefore may have frequent CMEs. Here we report the capture of a possible CME or chromospheric condensation on the RS CVn-type star II Pegasi (II Peg) using high-resolution spectroscopic observation. Two flares were detected during the observation, and the low limits of the flare energies are of the order of 10 ^33 erg and 10 ^34 erg, respectively. Using mean spectrum subtraction, the H _α residual shows red asymmetry during the flares, and the redshifted broad emission components are probably caused by chromospheric condensation or coronal rain. Moreover, a far redshifted extra emission component with a high bulk velocity of 429 km s ^−1 was observed during the second flare and is probably due to a prominence eruption. The velocity greatly exceeds the star’s escape velocity, which means that this eruption can develop into a CME. The CME mass is estimated to be 0.83–1.48 × 10 ^20 g, which is slightly larger than the value expected from solar flare-CME extrapolation. The kinetic energy of CME, derived to be 0.76–1.15 × 10 ^35 erg, is less than the kinetic energy extrapolated from solar events. Additionally, we could not completely rule out the possibility of chromospheric condensation resulting in the far redshifted extra emission. Finally, there is a blueshifted broad component in the subtracted H _α profile derived using synthesized spectral subtraction when no flare happened, and its behavior is associated with the H _α activity features.

We study the surface composition of asteroids with visible and/or infrared spectroscopy. For example, asteroid taxonomy is based on the spectral features or multiple color indices in visible and near-infrared wavelengths. The composition of asteroids gives key information to understand their origin and evolution. However, we lack compositional information for faint asteroids due to the limits of ground-based observational instruments. In the near future, the Chinese Space Survey Telescope (CSST) will provide multiple colors and spectroscopic data for asteroids of apparent magnitude brighter than 25 and 23 mag, respectively. With the aim of analyzing the CSST spectroscopic data, we applied an algorithm using artificial neural networks (ANNs) to establish a preliminary classification model for asteroid taxonomy according to the design of the survey module of CSST. Using the SMASS II spectra and the Bus–Binzel taxonomic system, our ANN classification tool composed of five individual ANNs is constructed, and the accuracy of this classification system is higher than 92%. As the first application of our ANN tool, 64 spectra of 42 asteroids obtained by us in 2006 and 2007 with the 2.16 m telescope in the Xinglong station (Observatory Code 327) of National Astronomical Observatory of China are analyzed. The predicted labels of these spectra using our ANN tool are found to be reasonable when compared to their known taxonomic labels. Considering its accuracy and stability, our ANN tool can be applied to analyze CSST asteroid spectra in the future.

Introduction: Some herbal ingredients can reshape the composition of the gut microbiome as well as its metabolites. At the same time, the gut microbiota can also affect drug metabolism. A large number of studies have reported that saponins are biotransformed under the action of intestinal microorganisms to improve drug efficacy and bioavailability. Capilliposide A is a triterpenoid saponin, which is derived from Lysimachia capillipes Hemsl. CPS-A has anti-inflammatory pharmacological activity, but the substance basis in vivo is unknown at present, so studies on the interaction between intestinal microorganisms and CPS-A may clarify the pharmacodynamic substance basis of CPS-A.Methods: This study established a colitis mouse model, collected sterile feces from normal mice and colitis mice, and incubated CPS-A with two different intestinal flora in vitro. Based on LC-MS, the metabolic process of CPS-A mediated by intestinal microbes and the intervention effect of CPS-A on intestinal microbiome derived metabolites were studied.Results: The results of experiments indicate that intestinal microorganisms can mediate the biotransformation of CPS-A and metabolize it into corresponding deglycosylation products, thereby promoting its drug effect. Not only that, CPS-A can also promote metabolites such as Deoxycholic acid, Histamine, 3-Hydroxytridecanoic acid, and Indole-3-acetic acid in the intestinal microbiota of mice with colitis. This may result in anti-colitis effects. CPS-A mainly involved in metabolic pathways such as azathioprine and mercaptopurine, which may also have beneficial or adverse effects.Discussion: This study on the interaction between CPS-A and microbiota provides a new idea for the study of traditional Chinese medicine with poor oral bioavailability. The regulatory effect of CPS-A on the metabolites of intestinal flora in colitis mice was also found. It laid a foundation for exploring the mechanism of action of saponins on colitis mice.

The direction estimation of the coherent source in a uniform circular array is an essential part of the signal processing area of the array, but the traditional uniform circular array algorithm has a low localization accuracy and a poor localization effect on the coherent source. To solve this problem, this paper proposes a two-dimensional direction of arrival (DOA) estimation for the coherent source in broadband. Firstly, the central frequency of the coherent sound source is estimated using the frequency estimation method of the delayed data, and a real-valued beamformer is constructed using the concept of the multiloop phase mode. Then, the cost function in the beam space is obtained. Finally, the cost function is searched in two dimensions to locate the sound source. In this paper, we simulate the DOA of the sound source at different frequencies and signal-to-noise ratios and analyze the resolution of the circular array. The simulation results show that the proposed algorithm can estimate the direction of arrival with high precision and achieve the desired results.

Introduction: Acoustic metasurfaces for underwater wave manipulation have great potential use, but the strong solid-fluid interaction caused by impedance closeness between the structure and water brings design difficulty, especially in the low-frequency range.Methods: Here a locally resonant metasurface for transmissive underwater acoustic waves is proposed using finite element method for which each metasurface unit consists of one channel and three subunits. Each subunit has one plate and two rubber spacers to form a resonator. By changing the height ratio of the plate over the subunit, arbitrary phase shifts within the full 2π coverage can be obtained at will with transmission ratio always higher than 60%.Results: Three applications, including asymmetric transmission, self-bending, and source illusion, are chosen to validate the design methodology.Discussion: Compared with previous transmissive type underwater metasurface, this design has the advantage of low frequency and simple fabrication. This work provides a novel paradigm of modulating waves for ocean exploration, underwater communication, and submarine stealth and antidetection.

We present the first Doppler images of the active eclipsing binary system SZ Psc, based on the high-resolution spectral data sets obtained in 2004 November and 2006 September-December. The least-squares deconvolution technique was applied to derive high signal-to-noise profiles from the observed spectra of SZ Psc. Absorption features contributed by a third component of the system were detected in the LSD profiles at all observed phases. We estimated the mass and period of the third component to be about 0.9M⊙ and 1283 ± 10 d, respectively. After removing the contribution of the third body from the least-squares deconvolved profiles, we derived the surface maps of SZ Psc. The resulting Doppler images indicate significant starspot activities on the surface of the K subgiant component. The distributions of star-spots are more complex than that revealed by previous photometric studies. The cooler K component exhibited pronounced high-latitude spots as well as numerous low- and intermediate-latitude spot groups during the entire observing seasons, but did not show any large, stable polar cap, different from many other active RS CVn-type binaries. [ABSTRACT FROM AUTHOR]

We present Doppler images of both components of the eclipsing binary system ER Vul, based on the spectra obtained in 2004 November, 2006 September and 2008 November. The least-squares deconvolution technique is used for enhancing the signal-to-noise ratios of the observed profiles. The new surface images reveal that both stars of ER Vul show strong starspot activities and the starspots appear at various latitudes. The surface maps of 2006 and 2008 both show the presence of large high-latitude starspots on each component of ER Vul. We find no obvious phase shift of the active regions during our observations. The longitude distributions of starspots are non-uniform on both stars. At low-to-mid latitudes, the active regions are almost exclusively found in the hemisphere facing the other star. However, we find no pronounced concentration of spots at the sub-stellar points. [ABSTRACT FROM AUTHOR]

Abstract: The high resolution, high S/N spectra for the chromospherically active binary AR Psc (=HD 8357) has been obtained by using the Coudé echelle spectrograph of the 2.16m telescope of Beijing Astronomical Observatory. The H α lines present emission above the continuum and the profiles of CaII IRT2 (λ 854.2nm) & IRT3 (λ 866.2nm) show core emission. The net chromospheric flux of the had been calculated by using spectral subtraction. A detailed spectroscopic analysis and model calculation have yielded the atmospheric parameters of the primary of AR Psc. The abundances of 9 elements has been obtained. And, the measurement of Magnetic field have been made using the Stenflo–Lindegren statistical analysis and the profile-addition technique. A magnetic field strength B =2400±300G and a filling factor α =0.45±0.05 are obtained. [Copyright &y& Elsevier]