Pulsating variables are prevalent in the classical δ Scuti instability strip of intermediate-age open star clusters. The cluster membership of these stars facilitates a comparative analysis of their evolution in analogous environments. In this study, we integrate ground-based observations, TESS Full Frame Images (FFIs), and Gaia DR3 data to investigate variable stars in the intermediate-age open star cluster NGC 2126. We performed ground-based time-series observations of NGC 2126 to identify variable stars within its vicinity. Next, we determined the membership of these stars using parallax and the proper motions from Gaia DR3 archive. Then, we searched the TESS Full Frame Images (FFIs) for counterparts to the variables identified above and performed their frequency analysis and classification. Finally, we modeled the light curves (LCs) of detected eclipsing binaries (EBs), including V551 Aur, which has a pulsating component. We found 25 members and 85 field variable stars. In TESS FFIs, we found LCs for 11 known variables and a new rotational variable. We determined that the pulsating EB V551 Aur is a member of the cluster. The low- and medium-resolution spectra revealed the line profile variation and the basic parameters for the star, respectively. Simultaneous modeling of the eclipses and the embedded pulsations resulted in improved orbital parameters for the binary system. We also report the determination of orbital parameters for the previously uncharacterized EB system UCAC4 700-043174.

Abstract We report on the detection of candidate optical counterpart GOTO23akf/AT2023shv to the GRB 230911A with the Gravitational-wave Optical Transient Observer (GOTO) instruments located at La Palma, Canary Islands, and Siding Spring Observatory, Australia. The Fermi Gamma-ray Burst Monitor, which finds gamma-ray bursts (GRBs) nearly every two days, detected GRB 230911A with a statistical uncertainty of 4.°1. However, the large (∼10–100 deg2) localization areas mostly impede the rapid identification of an optical counterpart. GOTO facilities fully covered 90% localization area of the GRB 230911A. We proposed GOTO23akf as the optical afterglow of GRB 230911A, subsequently confirmed through Swift-X-Ray Telescope observations in which an uncatalogued X-ray source spatially coincident with the GOTO candidate was detected. This is the first optical afterglow discovery for a Fermi GRB with the newly expanded GOTO network.

The National Astronomical Research Institute of Thailand (NARIT) has a manifold network of small telescopes installed worldwide. These telescopes serve educational and research purposes and are equipped mainly with CCD detectors for direct imaging and photometry. To extend the possible field of applications, several telescopes were fitted with commercially available medium-resolution spectrographs eShel from Shelyak. With these devices, researchers in NARIT obtained a versatile tool for stellar spectroscopy. Here we describe the current status of available equipment, possible ways of upgrading, and briefly introduce the achieved results of the asteroseismologic study of fast-rotating stars.

We report the results of a comprehensive study of the spectroscopic binary (SB2) system HD 34736 hosting two chemically peculiar (CP) late B-type stars. Using new and archival observational data, we characterize the system and its components, including their rotation and magnetic fields. Fitting of the radial velocities yields P-orb=83.(d)219(3) and e=0.8103(3). The primary component is a CP He-wk star with T-effA=13000 +/- 500 K and upsilon(e) sin i=75 +/- 3 km s(-1), while the secondary exhibits variability of Mg and Si lines, and has T-effB=11500 +/- 1000 K and upsilon(e)sin i=110-180 km s(-1). Transiting Exoplanet Survey Satellite and Kilodegree Extremely Little Telescope photometry reveal clear variability of the primary component with a rotational period P-rotA=1.d2799885(11), which is lengthening at a rate of 1.26(6) s yr(-1). For the secondary, P-rotB=0.d5226938(5), reducing at a rate of -0.14(3) s yr(-1). The longitudinal component < Bz > of the primary's strongly asymmetric global magnetic field varies from -6 to +5 kG. Weak spectropolarimetric evidence of a magnetic field is found for the secondary star. The observed X-ray and radio emission of HD 34736 may equally be linked to a suspected T Tau-like companion or magnetospheric emission from the principal components. Given the presence of a possible third magnetically active body, one can propose that the magnetic characteristics of the protostellar environment may be connected to the formation of such systems.

We present the results of a systematic search of the Transiting Exoplanet Survey Satellite (TESS) 2-min cadence data for new rapidly oscillating Ap (roAp) stars observed during the Cycle 2 phase of its mission. We find seven new roAp stars previously unreported as such and present the analysis of a further 25 roAp stars that are already known. Three of the new stars show multiperiodic pulsations, while all new members are rotationally variable stars, leading to almost 70 per cent (22) of the roAp stars presented being alpha(2) CVn-type variable stars. We show that targeted observations of known chemically peculiar stars are likely to overlook many new roAp stars, and demonstrate that multiepoch observations are necessary to see pulsational behaviour changes. We find a lack of roAp stars close to the blue edge of the theoretical roAp instability strip, and reaffirm that mode instability is observed more frequently with precise, space-based observations. In addition to the Cycle 2 observations, we analyse TESS data for all-known roAp stars. This amounts to 18 further roAp stars observed by TESS. Finally, we list six known roAp stars that TESS is yet to observe. We deduce that the incidence of roAp stars amongst the Ap star population is just 5.5 per cent, raising fundamental questions about the conditions required to excite pulsations in Ap stars. This work, coupled with our previous work on roAp stars in Cycle 1 observations, presents the most comprehensive, homogeneous study of the roAp stars in the TESS nominal mission, with a collection of 112 confirmed roAp stars in total.

We present the results of an asteroseismic study of HD 118660 (TIC 171729860), being a chemically peculiar (mild Am) star exhibiting $\delta$ Scuti ($\delta$ Sct) pulsations. It is based on the analysis of two sectors of time-series photometry from the space mission TESS (Transiting Exoplanet Survey Satellite) and seismic modelling. It yielded the detection of 15 and 16 frequencies for TESS sectors 23 and 50, respectively. The identified pulsation modes include four radial ($\ell =0$) and five dipolar ($\ell =1$) ones. The radial modes are overtones with order n ranging from 3 and 6. Such high values of n are theoretically not expected for stars with the effective temperature of HD 118660 ($T_{\rm eff}\approx 7550\,\rm K$) located near the red edge of the $\delta$ Sct instability strip. To estimate the asteroseismic parameters, we have generated a grid of stellar models assuming a solar metallicity ($Z=0.014$) and different values for the convective overshooting parameter ($0.1\le \alpha _{\rm ov}\le 0.3$). We conclude that the analysis of the radial modes is insufficient to constrain $\alpha _{\rm ov}$ and Z for $\delta$ Sct stars. The value for the equatorial velocity of HD 118660 derived from the seismic radius and the rotational frequency is consistent with values found in the literature.

WD 1145+017 is the first white dwarf known to be orbited by disintegrating exoasteroids. It is a helium -dominated white dwarf with lines of metals in spectra and variable asymmetric transits. The analysis of WD 1145 light curve allowed us to identify at least 8 bodies which periodically eclipse the star, showing periods ranging from 4.490 to 4.493 hours. Waterfall diagram shows that some of these periods are not stable. Estimating transit depths gave us possibility to assess the disintegration rate. We have estimated the lower limit of dust masses associated with these bodies, which exhibits time -varying characteristics, fluctuating within the range of approximately 2 - 3 x 10(14) kg.

ABSTRACT Developing an effective automatic classifier to separate genuine sources from artifacts is essential for transient follow-ups in wide-field optical surveys. The identification of transient detections from the subtraction artifacts after the image differencing process is a key step in such classifiers, known as real-bogus classification problem. We apply a self-supervised machine learning model, the deep-embedded self-organizing map (DESOM) to this ‘real-bogus’ classification problem. DESOM combines an autoencoder and a self-organizing map to perform clustering in order to distinguish between real and bogus detections, based on their dimensionality-reduced representations. We use 32 × 32 normalized detection thumbnails as the input of DESOM. We demonstrate different model training approaches, and find that our best DESOM classifier shows a missed detection rate of $6.6{{\ \rm per\,cent}}$ with a false-positive rate of $1.5{{\ \rm per\,cent}}$. DESOM offers a more nuanced way to fine-tune the decision boundary identifying likely real detections when used in combination with other types of classifiers, e.g. built on neural networks or decision trees. We also discuss other potential usages of DESOM and its limitations.

The powerful, high-energy magnetic activities of young stars play important roles in the magnetohydrodynamics in the innermost parts of the protoplanetary disks. In addition, the associated UV and X-ray emission dictates the photochemistry; moreover, the corona activities can affect the atmosphere of a newborn extrasolar planet. How the UV and X-ray photons are generated and how they illuminate the disks are not well understood. Here we report the analyses of the optical and infrared (OIR) photometric monitoring observations and the high angular resolution centimeter-band images of the low-mass (M1-type) pre-main-sequence star DM Tau. We found that the OIR photometric light curves present periodic variations, which suggests that the host young star is rotating in the same direction as the natal disk and is hosting at least one giant cold spot. In addition, we resolved that the ionized gas in the DM Tau disk is localized and its spatial distribution is varying with time. All the present observations can be coherently interpreted, if the giant cold spot is the dominant anisotropic UV and/or X-ray source that illuminates the ambient cone-like region. These results indicate that a detailed theoretical model of the high-energy protostellar emission is essential in understanding the space weather around extrasolar planets and the origin of life.

ABSTRACT We present a new study of the Algol-type eclipsing binary system AS Eri based on the combination of the MOST and TESS light curves and a collection of very precise radial velocities obtained with the spectrographs HERMES operating at the Mercator telescope, La Palma, and TCES operating at the Alfred Jensch telescope, Tautenburg. The primary component is an A3 V-type pulsating, mass-accreting star. We fitted the light and velocity data with the package phoebe, and determined the best-fitting model adopting the configuration of a semi-detached system. The orbital period has been improved using a recent (O-C) analysis and the phase shift detected between both light curves to the value 2.6641496 ± 0.0000001 d. The absence of any cyclic variation in the (O-C) residuals confirms the long-term stability of the orbital period. Furthermore, we show that the models derived for each light curve separately entail small differences, e.g. in the temperature parameter Teff,2. The high quality of the new solutions is illustrated by the residuals. We obtained the following absolute component parameters: L1 = 14.125 L⊙, M1 = 2.014 M⊙, R1 = 1.733 R⊙, log g1 = 4.264, L2 = 4.345 L⊙, M2 = 0.211 M⊙, R2 = 2.19 R⊙, log g2 = 3.078 with Teff,2/Teff,1 = 0.662 ± 0.002. Although the orbital period appears to be stable on the long term, we show that the light-curve shape is affected by a years-long modulation which is most probably due to the magnetic activity of the cool companion.

Eclipsing, spectroscopic double-lined (SB2) binaries remain to be the prime source of precise and accurate fundamental properties of stars. Furthermore, high-cadence spectroscopic observations of the eclipse phases allow us to resolve the Rossiter-McLaughlin effect whose modelling offers the means to probe spin-orbit misalignment in binaries. In this study, we develop the LSDBinary algorithm that is capable of working with both in-eclipse and out-of-eclipse spectra of SB2 binaries as input and delivers the LSD profiles, LSD-based model spectra, and precise RVs of both binary components as output. We offer an option to account for the Rossiter-McLaughlin effect in the calculation of the initial guess LSD profiles and components' flux ratio such that the effect can be modelled within the algorithm itself. We provide an extensive test of the LSDBinary software package on simulated spectra of artificial binaries. We study the effects of signal-to-noise-ratio of input spectra, resolving power of the instrument, uncertain atmospheric parameters of stars, and orbital properties of the binary system on the resulting LSD profiles and RVs measured from them. We find that atmospheric parameters have negligible effect on the shape of the computed LSD profiles while affecting mostly their global scaling. Our results are barely sensitive to signal-to-noise ratio of the input spectra provided they contain sufficient number of spectral lines, such as in A-type stars and later. Finally, the orbital inclination angle and components' radii ratio are found to have the largest effect on the shapes of the LSD profiles and RV curves extracted from them. The LSDBinary algorithm is specifically developed to perform detailed spectroscopic studies of eclipsing SB2 systems whose orbital configuration and components' atmospheric parameters are estimated by other means.

We present a review of the latest results of studies of the class of mass-accreting pulsating components of semi-detached eclipsing binaries known as oEA stars. The application of the techniques of asteroseismology to this class of stars unlocks new pathways for gaining a deeper understanding of the short-term evolution and magnetic activity of binary stars. We report the discovery of 49 new pulsating components of eclipsing binaries, based on data from NASA’s TESS space telescope. Recent observational results on the pulsation characteristics of these stars are summarized. The effects of the interaction of the magnetic and spot activity of the Roche-lobe-filling component of a system with the pulsations of the mass-accreting component are discussed.

We perform transit timing variation (TTV) and transmission spectroscopy analyses of the planet HAT-P-37b, which is a hot Jupiter orbiting a G-type star. Nine new transit light curves are obtained and analyzed together with 21 published light curves from the literature. The updated physical parameters of HAT-P-37b are presented. The TTV analyses show a possibility that the system has an additional planet that induced the TTVs amplitude signal of 1.74 ± 0.17 minutes. If the body is located near the 1:2 mean-motion resonance orbit, the sinusoidal TTV signal could be caused by the gravitational interaction of a sub-Earth-mass planet with mass of 0.06 M ⊕. From the analysis of an upper-mass limit for the second planet, a Saturn-mass planet with orbital period less than 6 days is excluded. The broadband transmission spectra of HAT-P-37b favors a cloudy atmospheric model with an outlier spectrum in the B filter.

We present and analyze 58 transit light curves of TrES-3b and 98 transit light curves of Qatar-1b, observed by the Transiting Exoplanet Survey Satellite, plus two transit light curves of Qatar-1b, observed by us, using a ground-based 1.23 m telescope. These light curves are combined with the best-quality light curves taken from the Exoplanet Transit Database and the literature. The precisely determined midtransit times from these light curves enable us to obtain the refined orbital ephemerides, with improved precision, for both hot Jupiters. From the timing analysis, we find indications of the presence of transit timing variations (TTVs) in both systems. Since the observed TTVs are unlikely to be short-term and periodic, the possibility of additional planets in orbits close to TrES-3b and Qatar-1b is ruled out. The possible causes of long-term TTVs, such as orbital decay, apsidal precession, the Applegate mechanism, and line-of-sight acceleration, are also examined. However, none of these possibilities are found to explain the observed TTV of TrES-3b. In contrast to this, line-of-sight acceleration appears to be a plausible explanation for the observed TTV of Qatar-1b. In order to confirm these findings, further high-precision transit and radial velocity observations of both systems would be worthwhile.

In this article, we present the new product and its description developed by the CoLiTec (Collection Light Technology) project (Khlamov & Savanevych 2020), called CoLiTecVS (CoLiTec Variable Stars) software as a set of tools for the automated light curve creation of variable stars using the sensor data received from the different sensors. CoLiTecVS allows performing the photometry and light curve creation with minimal user interaction in two different modes. The first one is an observation mode when the data are received online from the sensors directly and immediately processed by the OnLine Data Analysis System (OLDAS). This mode is called "OLDAS-Night "mode. The second one is processing the existing observations when sensor data are already received and saved. This mode is called "CoLiTec-Day " mode. Nowadays, the modern sensors (robotic ground-based telescopes equipped with different cameras with charge-coupled device (CCD)) still have a lack of capabilities, like non-uniform sensitivity of the matrix pixels, non-linearity of the pixel response to the number of photons that have fallen, oversaturation of bright objects leads to charge transfer to neighboring pixels and the presence of cold or hot pixels. All these shortcomings of modern sensors complicate the process of obtaining the accurate photometric measurements. Such lack of capabilities of modern sensors also makes the plotting of light curves a difficult and routine task. The latter shifts astronomer's main attention from research to the very time-consuming tasks of processing sensor data and light curve creation. To solve this problem, we developed a new tool for the automated reduction of photometric observations, which includes the computational method for the brightness assessment of the investigated and comparison stars; brightness equalization of astronomical images using an inverse median filter; and light curve plotting and its processing using different tools. This new CoLiTecVS software provides a tool for high accurate stellar brightness measuring and automated light curve creation with aperture photometry uncertainties less than 0.04 magnitude, the value of which generally depends on various imaging characteristics of telescopes, detectors, and sensors. CoLiTecVS has been tested on many different time series of 20-600 CCD-frames with variable stars and has produced high-quality photometric light curves in a fraction of the usual processing time. (C) 2022 The Author(s). Published by Elsevier B.V.

We present a study based on the high-resolution spectroscopy and K2 space photometry of five chemically peculiar stars in the region of the open cluster M44. The analysis of the high-precision photometric K2 data reveals that the light variations in HD 73045 and HD 76310 are rotational in nature and caused by spots or cloud-like co-rotating structures, which are non-stationary and short-lived. The time-resolved radial velocity measurements, in combination with the K2 photometry, confirm that HD 73045 does not show any periodic variability on timescales shorter than 1.3 d, contrary to previous reports in the literature. In addition to these new rotational variables, we discovered a new heartbeat system, HD 73619, where no pulsational signatures are seen. The spectroscopic and spectropolarimetric analyses indicate that HD 73619 belongs to the peculiar Am class, with either a weak or no magnetic field considering the 200 G detection limit of our study. The Least-Squares Deconvolution (LSD) profiles for HD 76310 indicate a complex structure in its spectra suggesting that this star is either part of a binary system or surrounded by a cloud shell. When placed in the Hertzsprung-Russell diagram, all studied stars are evolved from main-sequence and situated in the δ Scuti instability strip. The present work is relevant for further detailed studies of CP stars, such as inhomogeneities (including spots) in the absence of magnetic fields and the origin of the pulsational variability in heartbeat systems.

This White Paper summarises potential key science topics to be achieved with Thai National Radio Telescope (TNRT). The commissioning phase has started in mid 2022. The key science topics consist of "Pulsars and Fast Radio Bursts (FRBs)", "Star Forming Regions (SFRs)", "Galaxy and Active Galactic Nuclei (AGNs)", "Evolved Stars", "Radio Emission of Chemically Peculiar (CP) Stars", and "Geodesy", covering a wide range of observing frequencies in L/C/X/Ku/K/Q/W-bands (1-115 GHz). As a single-dish instrument, TNRT is a perfect tool to explore time domain astronomy with its agile observing systems and flexible operation. Due to its ideal geographical location, TNRT will significantly enhance Very Long Baseline Interferometry (VLBI) arrays, such as East Asian VLBI Network (EAVN), Australia Long Baseline Array (LBA), European VLBI Network (EVN), in particular via providing a unique coverage of the sky resulting in a better complete "uv" coverage, improving synthesized-beam and imaging quality with reducing side-lobes. This document highlights key science topics achievable with TNRT in single-dish mode and in collaboration with VLBI arrays.

Akahori, Takuya ID , Asanok, Kitiyanee ID , Baan, Willem ID , Bran, Sherin Hassan, Breen, L. Shari ID , Cho, Se-Hyung ID , Chanapote, Thanapol ID , Dodson, Richard ID , Ellingsen, P. Simon ID , Etoka, Sandra, Gray, D. Malcolm, Green, A. James, Hada, Kazuhiro ID , Halson, Marcus, Hirota, Tomoya ID , Honma, Mareki ID , Imai, Hiroshi ID , Johnston, Simon ID , Kim, Kee-Tae ID , Kramer, Michael ID , Li, Di ID , Macatangay, Ronald, Menten, M. Karl ID , Minh, Young Chol ID , Mkrtichian, David ID , Pimpanuwat, Bannawit ID , Richards, M.S. Anita ID , Rioja, Maria ID , Rujopakarn, Wiphu ID , Sakai, Daisuke ID , Sakai, Nobuyuki ID , Samanso, Nattida, Sanpa-arsa, Siraprapa, Semenko, Eugene ID , Sunada, Kazuyoshi ID , Surapipith, Vanisa, Thoonsaengngam, Nattaporn, Voronkov, A. Maxim ID , Wongphecauxson, Jompoj ID , Yadav, Ram Kesh, Zhang, Bo ID , Zheng, Xing Wu and Poshyachinda, Saran

The Gravitational-wave Optical Transient Observer (GOTO) is an array of wide-field optical telescopes, designed to exploit new discoveries from the next generation of gravitational wave detectors (LIGO, Virgo, KAGRA), study rapidly evolving transients, and exploit multimessenger opportunities arising from neutrino and very high energy gamma-ray triggers. In addition to a rapid response mode, the array will also perform a sensitive, all-sky transient survey with few day cadence. The facility features a novel, modular design with multiple 40-cm wide-field reflectors on a single mount. In June 2017 the GOTO collaboration deployed the initial project prototype, with 4 telescope units, at the Roque de los Muchachos Observatory (ORM), La Palma, Canary Islands. Here we describe the deployment, commissioning, and performance of the prototype hardware, and discuss the impact of these findings on the final GOTO design. We also offer an initial assessment of the science prospects for the full GOTO facility that employs 32 telescope units across two sites.

ABSTRACT We present the results of the high-resolution (R ∼ 60 000) spectroscopic analysis of the star LAMOSTJ045019.27 + 394758.7 (hereafter J045) from the list of carbon stars of LAMOST DR2. From our analysis, we find that J045 does not exhibit the spectral characteristics of carbon stars. It is found to be a metal-poor ([Fe/H] = −1.05) giant that shows very unusual elemental abundances, particularly for N, Na, V, and Zn. J045 shows α-elements (Mg, Si, Ca) with near-solar values (<[α/Fe]> = 0.09) in contrast to Galactic stars that show [α/Fe] in the range 0.2–0.3 dex. In J045, Sc and Ti are under abundant with [X/Fe] ≤ −0.25. Vanadium gives [V/Fe] = 0.51 and zinc is under-abundant with [Zn/Fe] = −0.62. The object exhibits near-solar abundances for Sr, Y, Ba, Pr, and Sm. The La is marginally enhanced, and Ce and Nd are marginally under-abundant in J045. With [Ba/Eu] = −0.38, the object falls into the category of neutron-capture rich r-I stars. The estimated abundances of various elements show that the observed abundance pattern is not compatible with the abundances characteristic of Galactic metal-poor stars but matches quite closely with the abundance pattern of Sculptor Dwarf galaxy stars of similar metallicity. Based on the above observational evidences, we suggest that the object is a possible Sculptor Dwarf Galaxy escapee.