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All stellar-mass black holes have hitherto been identified by X-rays emitted from gas that is accreting onto the black hole from a companion star. These systems are all binaries with a black-hole mass that is less than 30 times that of the Sun 1 – 4 . Theory predicts, however, that X-ray-emitting systems form a minority of the total population of star–black-hole binaries 5 , 6 . When the black hole is not accreting gas, it can be found through radial-velocity measurements of the motion of the companion star. Here we report radial-velocity measurements taken over two years of the Galactic B-type star, LB-1. We find that the motion of the B star and an accompanying Hα emission line require the presence of a dark companion with a mass of 68 − 13 + 11 solar masses, which can only be a black hole. The long orbital period of 78.9 days shows that this is a wide binary system. Gravitational-wave experiments have detected black holes of similar mass, but the formation of such massive ones in a high-metallicity environment would be extremely challenging within current stellar evolution theories. Radial-velocity measurements of a Galactic B-type star show a dark companion that seems to be a black hole of about 68 solar masses, in a widely spaced binary system.

The Chinese Hα Solar Explorer (CHASE), dubbed “Xihe”—Goddess of the Sun, was launched on October 14, 2021 as the first solar space mission of China National Space Administration (CNSA). The CHASE mission is designed to test a newly developed satellite platform and to acquire the spectroscopic observations in the Hα waveband. The Hα Imaging Spectrograph (HIS) is the scientific payload of the CHASE satellite. It consists of two observational modes: raster scanning mode and continuum imaging mode. The raster scanning mode obtains full-Sun or region-of-interest spectral images from 6559.7 to 6565.9 Å; and from 6567.8 to 6570.6 Å with 0.024 Å pixel spectral resolution and 1 min temporal resolution. The continuum imaging mode obtains photospheric images in continuum around 6689 Å with the full width at half maximum of 13.4 Å. The CHASE mission will advance our understanding of the dynamics of solar activity in the photosphere and chromosphere. In this paper, we present an overview of the CHASE mission including the scientific objectives, HIS instrument overview, data calibration flow, and first results of on-orbit observations.

The Hα line is an important optical line in solar observations containing the information from the photosphere to the chromosphere. To study the mechanisms of solar eruptions and the plasma dynamics in the lower atmosphere, the Chinese Hα Solar Explorer (CHASE) was launched into a Sun-synchronous orbit on October 14, 2021. The scientific payload of the CHASE satellite is the Hα Imaging Spectrograph (HIS). The CHASE/HIS acquires, for the first time, seeing-free Hα spectroscopic observations with high spectral and temporal resolutions. It consists of two observational modes. The raster scanning mode provides full-Sun or region-of-interest spectra at Hα (6559.7–6565.9 Å) and Fe I (6567.8–6570.6 Å) wavebands. The continuum imaging mode obtains full-Sun photospheric images at around 6689 Å. In this paper, we present detailed calibration procedures for the CHASE/HIS science data, including the dark-field and flat-field correction, slit image curvature correction, wavelength and intensity calibration, and coordinate transformation. The higher-level data products can be directly used for scientific research.

Over the past five years, the Bosscha Observatory in Bandung, Indonesia, has dedicated significant attention to studying B-emission (Be) stars exhibiting distinctive emission characteristics. In this work, we meticulously analyzed the spectra originating from three prominent Be stars: Delta Scorpii, Eta Centauri, and Kappa Lupi. We also took additional spectrum data from the BeSS repository for each of the three stars to maximize our analysis results. Our analysis revolved around quantifying crucial spectral attributes, including the emission peak centers, the equivalent width (EW), and the full width at half maximum (FWHM). These parameters proved pivotal for deriving the violet-to-red peak intensity ratio (V/R), emission-to-continuum ratio (E/C), and the star’s radial velocity. Based on our analysis, there are several things to be pointed out. For all stars, there was no such significant variation in E/C values. Our single-peak analysis of δ Sco showed a strong emission primarily caused by the presence of a circumstellar disk of gas. FWHM of Hα in κ Lup demonstrated minor variability with time, meanwhile FWHM of Hα in η Cen decreased with time and orbital phase. Much more intense observations and analysis should provide better data to conclude the variability pattern of those parameters.

Pulsating stars show variability in brightness due to changes in their volume. There are two types of pulsation/oscillation: radial and non-radial. Radial oscillation keeps the symmetrical shape of the star, while non-radial oscillation does not. We study a pulsating star: γ Cas, classified as a B0.5 IVe variable star because of its pulsations and also an emission star due to the emission lines in its spectra. When a star pulsates, its atmosphere expands and contracts, potentially leading to the formation of shock waves. Observational features such as discontinuities in the radial velocity curve and emission lines support this phenomenon. In this study, we analyse the relationship between pulsation motion and the H α emission lines of γ Cas using photometric and spectroscopic data. Photometric data is obtained from the BRIght Target Explorer (BRITE) catalog, while spectroscopic data comes from the Be Star Spectra (BeSS) catalog. Both datasets cover the same observational dates: August 28 to October 26, 2015. Confirming the pulsation period of γ Cas at 1.21 days, we also discover an added pulsation period of 10 days from photometric data. To confirm this, we examine spectroscopic data from three specific dates: August 28, September 7, and 27, 2015. Notably, the relative flux of the H α emission lines continue to increase, leading us to conclude that these lines are indeed caused by the pulsation of γ Cas.

The beam oscillation of J-PARC ion source is being studied as AC electric field at 2 MHz ion source driving frequency can directly change the extraction characteristics of both H − ions and electrons. The internal RF antenna inducing the electric field generated two peaks of plasma production during one RF cycle as confirmed by 4 MHz modulation of Balmer-alpha (Hα) emission intensity. The coupling between the plasma production at 4 MHz and the oscillation of the local plasma potential in the vicinity of the extraction hole at 2 MHz can cause 6 MHz oscillation, which was observed in the measurement of extraction current from the ion source. Phase-delay of Hα intensities from the source plasma and those of the extraction electron current were compared with the RF input signal to the amplifier.

We present new high-spectral resolution échelle spectra of IC 4997 obtained in 2023 June to study the evolution of its recently reported variable Hα emission line profile. Compared with similar spectra from 2020 September, the new ones also show a single-peaked profile but the full velocity width of the Hα wings has increased by a factor of; 1.2. Besides, we use our high-resolution échelle spectra to investigate the internal kinematics of the nebula. Preliminary analysis suggests that the two shells of IC 4997 are kinematically resolved: the outer shell expands at; 10–14 km s-1 and the inner shell at; 25 km s-1.

In this article, the results of an experimental study of non-equilibrium radiation of pure argon are presented. These results were obtained at the Institute of Mechanics of Lomonosow Moscow State University Shock Tube experimental complex. The main attention is focused to the study of the initial phase of radiation take place before the sharp increase electron concentration. The electron number density was determined with using of Stark broadening of Hα hydrogen line method. The panoramic spectra and individual radiation line evolution are presented. It is noted that radiation evolution at the initial stage depends strongly from radiation wavelength.

In the present contribution, a spectroscopic investigation is used to study a plasma generated by fundamental radiation from a Q-switched Nd:YAG laser focused onto a zinc-based alloy. The quantification using calibration-free laser-induced breakdown spectroscopy (CF-LIBS) relies on the assumption of local thermodynamic equilibrium (LTE). The main objectives of this research are to investigate the spatial and temporal evolution of plasma parameters (Te, Ne) and assess the fulfillment of LTE conditions within specific regions. For an accurate plasma parameters estimation, only delay times ranging from 0.8 to 6 µs and for axial distances from 0.6 to 2.6 mm were chosen. Under these conditions, spectra were characterized by atomic and ionic emissions. Plasma temperature values were determined using the Saha–Boltzmann method applied to neutral and singly ionized copper lines, while the electron number density was calculated using the Stark broadened profile of the H α line, according to the Gigosos relation. The LTE condition was warranted using the McWhirter criterion as long as two other conditions, which take into account the transient and heterogeneous nature of the plasma. CF-LIBS quantification was carried out under optimized spatiotemporal conditions and was compared with micro-X-ray fluorescence measurements. The relative error values of CF-LIBS quantification indicate an acceptable precision of our preliminary results.

The Hα imaging spectrograph (HIS) is the scientific payload of the first solar space mission, the Chinese Hα solar explorer (CHASE), supported by the China National Space Administration (CNSA). The CHASE/HIS achieves, for the first time in space, Hα spectroscopic observations with high spectral and temporal resolutions. Separate channels for the raster scanning mode (RSM) and continuum imaging mode (CIM) are integrated into one, and a highly integrated design is achieved through multiple folding of the optical path and ultra-light miniaturized components. The design of HIS implements a number of key technologies such as high-precision scanning of the optical field of view (FOV), high-precision integrated manufacturing inspection, a large-tolerance pre-filter window, and full-link solar radiation calibration. The HIS instrument has a pixel spectral resolution of 0.024 Å and can complete a full-Sun scanning within 46 s.