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An H O maser flare detected in July 2023 in the star-forming region DR21OH when monitoring the continuum emission in DR21 with PRAO RT22 is reported. These observations were part of a program to study the characteristics of the antenna and the atmospheric absorption at a wavelength of 1.35 cm. Subsequent access to archival data and new measurements have shown that the detected flare in 2023 was not the only one in the source, and DR21OH is highly variable in the H O line at 22 GHz with a rather unpredictable character. Based on continuum measurements in DR21, we have estimated the effective area of RT22. [ABSTRACT FROM AUTHOR]

We present observations of population anti-inversion in the 31 − 40 A + transition of CH3OH (methanol) at 107.013831 GHz toward the Galactic center cloud G0.253+0.016 ("The Brick"). Anti-inversion of molecular level populations can result in absorption lines against the cosmic microwave background (CMB) in a phenomenon known as a "dasar." We model the physical conditions under which the 107 GHz methanol transition dases and determine that dasing occurs at densities below 106 cm−3 and column densities between 1013 and 1016 cm−2. We also find that for this transition, dasing does not strongly depend on the gas kinetic temperature. We evaluate the potential of this tool for future deep galaxy surveys. We note that other works have already reported absorption in this transition (e.g., in NGC 253), but we provide the first definitive evidence that it is absorption against the CMB rather than against undetected continuum sources. [ABSTRACT FROM AUTHOR]

We report a measurement of the trigonometric parallax of 22 GHz water masers in the massive star-forming region G034.43+0.24 as part of the Bar and Spiral Structure Legacy Survey using the Very Long Baseline Array. The parallax is 0.330 ± 0.018 mas, corresponding to a distance of 3.03 − 0.16 + 0.17 kpc. This locates G034.43+0.24 near the inner edge of the Sagittarius spiral arm and at one end of a linear distribution of massive young stars that cross nearly the full width of the arm. The measured three-dimensional motion of G034.43+0.24 indicates a near-circular Galactic orbit. The water masers display arc-like distributions, possibly bow shocks, associated with winds from one or more massive young stars. [ABSTRACT FROM AUTHOR]

We report the proper motions of 22 GHz water masers toward W49 N that were observed by the KVN and VERA Array (KaVA) during 2017 February–May. We found 263, 268, and 310 features in three successive epochs; they were distributed in a region of size 4 × 4 arcsec2. The strongest flux density was in the third epoch, and its averaged value was 18,090 Jy at V LSR +0.47 km s−1. For 102 H2O maser features, proper motion was detected across all three epochs. The average proper motions in R.A. and decl. offset were −0.352 and +0.890 mas yr−1, respectively. The morphology of the distribution of the H2O maser features was found to be a bipolar outflow structure with an inclination angle of 37° ± 13° to the line of sight, and the features were expanding from a well-defined outflow center. A model of the source combining expansion and rotation yielded a distance to W49 of 11.12 ± 0.96 kpc that is consistent with the results from trigonometric parallax. A redshifted lobe was situated in the northeast direction and a blueshifted lobe in the southwest direction. We also discussed the location of the powerful flaring H2O maser feature at V LSR = + 6 km s−1 and its possible mechanisms on the basis of spatial structures for the maser feature in VLBI maps observed with the KaVA, timed just before and during the rebrightening phase. [ABSTRACT FROM AUTHOR]

We are pleased to summarise the IAU Symposium 380, Cosmic Masers: Proper Motion toward the Next-Generation Large Projects held on March 2023 March 20-24 in Kagoshima City, Japan. It is the sixth symposium focusing on astrophysical masers broadly used in research of star formation and evolved stars, astrometric measurements of the Milky Way galaxy, as well as studies of extragalactic environments. [ABSTRACT FROM AUTHOR]

Many astrophysical phenomena can only be studied in detail for objects in our galaxy, the Milly Way, but we know much more about the structure of thousands of nearby galaxies than we do about our own Galaxy. Accurate distance measurements in the Milky Way underpin our ability to understand a wide range of astrophysical phenomena and this requires observations from both the northern and southern hemisphere. Our ability to measure accurate parallaxes to southern masers has been hampered a range of factors, in particular the absence of a dedicated, homogeneous VLBI array in the south. We have recently made significant advances in astrometric calibration techniques which allow us to achieve trigonometric parallax accuracies of around 10 micro-arcseconds (μ as) for 6.7 GHz methanol masers with a hetrogeneous array of 4 antennas. We outline the details of this new "multiview" technique and present the first trigonometric parallax measurements that utilise this approach. [ABSTRACT FROM AUTHOR]

Single-dish observations at centimeter wavelengths have suggested that the Sgr B2 molecular cloud at the Galactic Center hosts weak maser emission from several large molecules. Here, we present the interferometric observations of the Class I methanol (CH3OH) maser at 84 GHz, the methanimine (CH2NH) maser at 5.29 GHz, and the methylamine (CH2NH2) maser at 4.36 GHz toward Sgr B2 North (N). We use a Bayesian approach to quantitatively assess the observed masing spectral profiles and the excitation conditions. By comparing the spatial origin and extent of maser emission from several molecular species, we find that the new maser transitions have a close spatial relationship with the Class I masers, which suggests a similar collisional pumping mechanism. [ABSTRACT FROM AUTHOR]

Astrometric very long baseline interferometry (VLBI) observations of stellar masers are an excellent method to determine distances and proper motions in our Galaxy. Large maser astrometry surveys, the Bar and Spiral Structure Legacy survey and the VLBI Exploration for Radio Astrometry, allowed astronomers to determine fundamental Galactic parameters, such as the rotation curve and the distance to the Galactic centre, as well as to trace the spiral arms. In this review, the results of these surveys will be summarised and compared with astrometric measurements using other methods. [ABSTRACT FROM AUTHOR]

The ALMA Project is embarking on a partner-wide initiative to at least double, and ultimately quadruple the correlated bandwidth of ALMA by @2030. This initiative is called the ALMA Wideband Sensitivity Upgrade (WSU). In this contribution, I briefly describe the main aspects of the upgrade and status. Then I provide several examples of how the WSU will enhance (sub)millimeter maser science by affording the ability to observe more diagnostic maser transitions (and thermal lines) with a single observation. [ABSTRACT FROM AUTHOR]

Maser effects occur in recombination lines when the plasma departs from local thermodynamic equilibrium (LTE). Its consequence is not as dramatic as that found in molecular masers, and therefore it is more difficult to recognize. Besides, it occurs in compact high density regions, and its lines fall at millimeter and submillimeter wavelengths, only recently available with good angular resolution. This review will focus on the theoretical aspects of maser recombination lines and on the recent detection of these masers in different astronomical objects. [ABSTRACT FROM AUTHOR]

We present the results of KVN Key Science Program (KSP) for evolved stars, which was launched in 2014. The first phase of KSP ended in June 2020 and the second phase started in October 2020. The goal of KSP is to study the physical characteristics of the evolved stars by observing the spatial distribution and temporal variability of the stellar masers at four frequency-bands (K, Q, W and D bands). The 22 GHz H2O maser is usually observed from the outer part of circumstellar envelopes compared to the 43, 86, 129 GHz SiO masers, thus the kinematic links between these regions can be studied by the multi-frequency simultaneous observations of KSP along the stellar pulsation cycles. This eventually enable us to study the enormous mass-loss rate of evolved stars, and the accumulated results from KSP are expected to shed light on the study of the late stage of the stellar evolution. [ABSTRACT FROM AUTHOR]

Maser properties can be measured with milli-arcsec precision over multiple epochs using ALMA, cm- and mm-wave VLBI and e-MERLIN. This allows: (i) Tracing SiO maser proper motions in the pulsation-dominated zone; (ii) Quantifying clumpiness, variability and asymmetry of the wind traced by masers; (iii) Contrasting behaviour from OH masers even at similar distances from the star; (iv) Measuring magnetic fields. Mass lost from the star, traced by SiO masers, is likely to take decades to reach ∼5 stellar radii. At 5–50 stellar radii, once dust is well formed, 22-GHz H2O masers show the wind accelerating through the escape velocity; its overall direction is away from the star but the velocity field is complex. In a few cases (so far), highly-directed, localised ejecta are seen. Magnetic fields appear to be stellar-centred and strong enough to influence wind kinematics. Recent ALMA and other observations have shown that otherwise inconspicuous companions shape a majority of evolved star winds, whilst advanced models demonstrate how, for some situations, this is compatible with masers showing negligible rotation proper motions. The long-term monitoring achievable at radio frequencies complements the multi-transition maser studies and analysis of thermal lines and dust at shorter wavelengths. [ABSTRACT FROM AUTHOR]

Water is a ubiquitous molecule in circumstellar envelopes (CSEs). Its emission has been detected at a wide range of distances from the central oxygen-rich evolved star. In particular, the water maser transition at 22 GHz, typically extending from about 5–20 stellar radii to as far as several hundred stellar radii from the star, has been commonly used to probe the structure and dynamics of the intermediate regions of the CSE where dust is condensing and the inner wind is being accelerated. The advent of ALMA has opened the door to high-angular resolution mapping of much higher excitation transitions of water, probing the inner regions of the CSEs, some of which are anticipated to exhibit maser action. The ALMA ATOMIUM large program observed many such transitions towards a sample of AGB stars & red supergiants. The preliminary results show that while some transitions depart only slightly from LTE, others clearly show signs of maser action. The Gaussian fitting of the non-diffuse/compact part of some of the (quasi) thermal & maser transitions reveal interesting velocity gradients, signatures of outflowing and infalling motions hence providing important constraints for stellar wind models. [ABSTRACT FROM AUTHOR]

Astrometric observations of maser sources in the Milky Way, using the Very Long Baseline Interferometry (VLBI) technique, have been exploited to determine the spiral structure of our Galaxy. Several major spiral arms have now been pinpointed in the first and second Galactic quadrants. Fundamental Galactic parameters such as the distance to the Galactic Centre and the rotation curve and speed have been determined. In this review, we discuss the latest results from the Bar and Spiral Structure Legacy survey, the VLBI Exploration of Radio Astrometry survey and other VLBI arrays and compare them with astrometric measurements of stars from the Gaia mission. In particular, we present the peculiarities of the individual spiral arms and a thorough discussion of the methods to determine different Galactic parameters as well as the obtained values. [ABSTRACT FROM AUTHOR]

Ventspils International Radio Astronomy Centre (Ventspils University of Applied Sciences) is implementing the scientific project "Complex Investigations of the Small Bodies in the Solar System" (lzp-2018/1-0401) related to the research of the small bodies in the Solar system (mainly, focusing on asteroids and comets) using methods of radio astronomy and signal processing. One of the research activities is weak hydroxyl (OH) radical observation in the radio range – single antenna observations using Irbene RT-32 radio telescope. To detect weak (0.1 Jy) OH masers of astronomical objects using radio methods, a research group in Ventspils adapted the Irbene RT-32 radio telescope working at 1665.402 and 1667.359 MHz frequencies. Spectral analysis using Fourier transform and continuous wavelet transform was applied to radio astronomical data from multiple observations related to weak OH maser detection. Multiple observation sessions of OH maser objects (R LMi, RU Ari, V524 Cas, OH 138.0+7.2, U Aur, etc) were carried out in 2020–2021. [ABSTRACT FROM AUTHOR]

The collisional pumping of H O and СH OH masers in magnetohydrodynamic nondissociative C-type shocks is considered. A grid of C-type shock models with speeds in the range 5–70 km s and preshock gas densities – cm is constructed. The large velocity gradient approximation is used to solve the radiative transfer equation in molecular lines. The para-H O 183.3 GHz and ortho-H O 380.1 and 448.0 GHz transitions are shown to be inverted and to have an optical depth along the shock velocity at relatively low gas densities in the maser zone, – cm . Higher gas densities, cm , are needed for efficient pumping of the remaining H O masers. Simultaneous generation of H O and class I СH OH maser emission in a shock is possible at preshock gas densities cm and shock speeds in the range km s . The possibility of detecting class I СH OH and para-H O 183.3 GHz masers in star-forming regions and near supernova remnants is investigated. [ABSTRACT FROM AUTHOR]

High brightness-temperature radiation is observed in various astrophysical sources: active galactic nuclei, pulsars, interstellar masers, and flaring stars; the discovery of fast radio bursts renewed interest in the nonlinear interaction of intense radiation with plasma. In astronomical systems, the radiation frequency is typically well above the plasma frequency and its spectrum is broad, so nonlinear processes differ considerably from those typically studied in laboratory plasma. This paper is the first in a series devoted to the numerical study of nonlinear interactions of electromagnetic waves with plasma. We start with nonmagnetized pair plasmas, where the primary processes are induced (Compton) scattering and filamentation instability. In this paper, we consider waves in which electron oscillations are nonrelativistic. Here, the numerical results can be compared to analytical theory, facilitating the development of appropriate numerical tools and framework. We distill the analytic theory, reconciling the plasma and radiative transfer pictures of induced scattering and developing in detail the kinetic theory of modulation/filamentation instability. We carry out homogeneous numerical simulations using the particle-in-cell codes EPOCH and Tristan-MP for both monochromatic waves and wave packets. We show that simulations of both processes are consistent with theoretical predictions, setting the stage for analyzing the highly nonlinear regime. [ABSTRACT FROM AUTHOR]

We are interested in quantum calculations of polarization transfer (PT) rates due to collisions of the SiO molecule with the electrons. We determine the inelastic PT rates associated to the transitions: X 1 Σ + → 3 Π ; X 1 Σ + → 3 Σ + ; X 1 Σ + → 3 Δ ; X 1 Σ + → 3 Σ − . In addition, we calculate the elastic PT rates due to rotational transitions inside the electronic state X 1 Σ + which are related to observed astronomical SiO MASERs. Our PT rates are obtained through linear combination of excitation rates previously calculated for SiO-electron collisions. The calculations are performed on a collision energy grid large enough to ensure converged state-to-state rates for temperatures ranging from 1000 to 10,000 K for inelastic rates and from 5 to 5000 K for elastic rates. The dependence of the inelastic rates on temperatures is obtained analytically and given in useful form. [ABSTRACT FROM AUTHOR]

We consider a magnetar flare model for fast radio bursts (FRBs). We show that millisecond bursts of sufficient power can be generated by synchrotron maser emission ignited at the reverse shock propagating through the weakly magnetized material that forms the magnetar flare. If the maser emission is generated in an anisotropic regime (due to the geometry of the production region or presence of an intense external source of stimulating photons), the duration of the maser flashes is similar to the magnetar flare duration even if the shock front radius is large. Our scenario allows for relaxing the requirements for several key parameters: the magnetic field strength at the production site, luminosity of the flare, and the production site bulk Lorentz factor. To check the feasibility of this model, we study the statistical relation between powerful magnetar flares and the rate of FRBs. The expected ratio is derived by convoluting the redshift-dependent magnetar density with its flare luminosity function above the energy limit determined by the FRB detection threshold. We obtain that only a small fraction, ∼10âˆ'5, of powerful magnetar flares trigger FRBs. This ratio agrees surprisingly well with our estimates: we obtained that 10% of magnetars should be in the evolutionary phase suitable for the production of FRBs, and only 10âˆ'4 of all flares are expected to be weakly magnetized, which is a necessary condition for the high-frequency maser emission. [ABSTRACT FROM AUTHOR]

IRAS 20126+4104 is an extensively studied high-mass star-forming region with many astrophysical maser lines from methanol and water molecules. The brightest and highly variable is the 6.7 GHz methanol maser transition. We present follow-up studies on this target including the monitoring with the Irbene radio telescope with high-cadence data and European VLBI Network imaging extending the VLBI monitoring to 19 years. We also plan to study the target in the future based on its variability, both in the radio domain (EVN observations are planned for June 2023) and in infra-red with the 1 meter Kagoshima University Telescope operated by Amanogawa Galaxy Astronomy Research Center (AGARC). [ABSTRACT FROM AUTHOR]

An elaborate variational procedure of reduced dimensionality based on explicitly correlated coupled clusters calculations is applied to understand the far infrared spectrum of ethylene-glycol, an astrophysical species. This molecule can be classified in the double molecular symmetry group G8 and displays nine stable conformers, gauche and trans. In the gauche region, the effect of the potential energy surface anisotropy due to the formation of intramolecular hydrogen bonds is relevant. For the primary conformer, stabilized by a hydrogen bond, the ground vibrational state rotational constants are computed to be A0 = 15 369.57 MHz, B0 = 5579.87 MHz, and C0 = 4610.02 MHz corresponding to differences of 6.3 MHz, 7.2 MHz, and 3.5 MHz from the experimental parameters. Ethylene glycol displays very low torsional energy levels whose classification is not straightforward and requires a detailed analysis of the torsional wavefunctions. Tunneling splittings are significant and unpredictable due to the anisotropy of the potential energy surface PES. The ground vibrational state splits into 16 sublevels separated ~142 cm-1. The splitting of the "G1 sublevels" was calculated to be ~0.26 cm-1 in very good agreement with the experimental data (0.2 cm-1 = 6.95 MHz). Transitions corresponding to the three internal rotation modes allow assignment of previously observed Q branches. Band patterns, calculated between 362.3 cm-1 and 375.2 cm-1, 504 cm-1 and 517 cm-1, and 223.3 cm-1 and 224.1 cm-1, that correspond to the tunnelling components of the v21 fundamental (v21 = OH-torsional mode), are assigned to the prominent experimental Q branches. [ABSTRACT FROM AUTHOR]

Astrometric observations of maser sources in the Milky Way, using the Very Long Baseline Interferometry (VLBI) technique, have been exploited to determine the spiral structure of our Galaxy. Several major spiral arms have now been pinpointed in the first and second Galactic quadrants. Fundamental Galactic parameters such as the distance to the Galactic Centre and the rotation curve and speed have been determined. In this review, we discuss the latest results from the Bar and Spiral Structure Legacy survey, the VLBI Exploration of Radio Astrometry survey and other VLBI arrays and compare them with astrometric measurements of stars from the Gaia mission. In particular, we present the peculiarities of the individual spiral arms and a thorough discussion of the methods to determine different Galactic parameters as well as the obtained values.

We have used catalogues from several Galactic plane surveys and dedicated observations to investigate the relationship between various maser species and Galactic star-forming clumps, as identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. The maser transitions of interest are the 6.7 and 12.2-GHz methanol masers, 22.2-GHz water masers, and the masers emitting in the four ground-state hyperfine structure transitions of hydroxyl. We find clump association rates for the water, hydroxyl and methanol masers to be 56, 39, and 82 per cent, respectively, within the Galactic longitude range of 60○ > ℓ > −60○. We investigate the differences in physical parameters between maser associated clumps and the full ATLASGAL sample, and find that clumps coincident with maser emission are more compact with increased densities and luminosities. However, we find the physical conditions within the clumps are similar for the different maser species. A volume density threshold of n (H2) > 104.1 cm−3 for the 6.7-GHz methanol maser found in our previous study is shown to be consistent across for all maser species investigated. We find limits that are required for the production of maser emission to be 500 L⊙ and 6 M⊙, respectively. The evolutionary phase of maser associated clumps is investigated using the L / M ratio of clumps coincident with maser emission, and these have similar L / M ranges (∼100.2−102.7 L⊙/M⊙) regardless of the associated transitions. This implies that the conditions required for the production of maser emission only occur during a relatively narrow period during a star's evolution. Lower limits of the statistical lifetimes for each maser species are derived, ranging from ∼0.4−2 × 104 yr and are in good agreement with the 'straw man' evolutionary model previously presented. [ABSTRACT FROM AUTHOR]

Radio campaigns using maser stellar beacons have provided crucial information to characterize Galactic stellar populations. Currently, the Bulge Asymmetries and Dynamical Evolution (BAaDE) project is surveying infrared (IR) color-selected targets for SiO masers. This provides a sample of evolved stars that can be used to study the inner, optically obscured Galaxy using line-of-sight velocities and possibly very long baseline interferometry proper motions. In order to use the BAaDE sample for kinematic studies, the stellar population should be characterized. In this study, the BAaDE targets have been cross-matched with IR (2MASS) and optical (Gaia) samples. By exploring the synergies of this cross-match together with Gaia parallaxes and extinction maps, the local (d < 2 kpc) asymptotic giant branch (AGB) stars can be characterized. We have defined a BAaDE–Gaia sample of 20,111 sources resulting from cross-matching BAaDE targets with IR and optical surveys. From this sample, a local sample of 1812 evolved stars with accurate parallax measurements, confirmed evolved stellar evolution stage, and within 2 kpc distance around the Sun was selected, for which absolute (bolometric) magnitudes are estimated. The evolved stellar population with Gaia counterparts that are variable seems to be predominantly associated with AGB stars with moderate luminosity () and periods between 250 and 1250 days. [ABSTRACT FROM AUTHOR]

We report a systemic search for nonmetastable NH3 masers toward a high-mass star-forming region Sgr B2(N) using the Shanghai 65 m Tianma radio telescope with its Ku-band (12–18 GHz) and K-band (18–26.5 GHz) receivers. A total of 18 maser emission transitions were detected, and eight of these are newly identified NH3 maser transitions in interstellar space. Most (five) of the new maser transitions were found from the Ku-band observations which were absent from previous searches. Rotation diagram analysis for the 18 quasi-thermal transitions derived a high gas kinematic temperature (∼400 K) and an extremely high H2 column density (∼5 × 1025 cm−2). Such conditions suggest that the NH3 masers are likely pumped by vibrational excitation. Compared with quiet maser activity observed more than 20 yr ago, NH3 masers may be bursting in our observation time when the gas kinematic temperature might increase from ∼150 to ∼400 K. As extreme conditions (either high gas kinematic temperature and/or high gas column density) are required to excite nonmetastable NH3 masers, it can be argued that the detected NH3 maser outburst may be linked to a more intensive accretion-burst event from an high-mass young stellar object in the Sgr B2(N) region. [ABSTRACT FROM AUTHOR]

The collisional pumping of OH masers in non-dissociative C-type shocks near supernova remnants is considered. The emergence of maser emission in OH lines is investigated for various shock parameters—the shock speed, the preshock gas density, the cosmic-ray ionization rate, and the magnetic field strength. The largest optical depth in the 1720 MHz line is reached at high gas ionization rates s , an initial density cm , and a shock speed km s . According to our calculations, there is also a level population inversion for the 6049 and 4765 MHz transitions of excited OH rotational states. However, the optical depth in these lines is small for all of the investigated shock parameters, which explains the non-detection of maser emission in these lines in supernova remnants. [ABSTRACT FROM AUTHOR]

We consider the radiation properties and processes of a gas with a population inversion using the formalism based on the Maxwell–Bloch equations. We focus on the maser action and Dicke's superradiance to establish their relationship in the overall radiation process during the temporal evolution of the system as a function of position. We show that the maser action and superradiance are not competing phenomena but are rather complementary and define two distinct limits for the intensity of radiation. Masers characterize the quasi-steady state limit, when the population inversion density and the polarization amplitude vary on time-scales longer than those of non-coherent processes affecting their evolution (e.g. collisions), while superradiance defines the fast transient regime taking place when these conditions are reversed. We show how a transition from a maser regime to superradiance will take place whenever a critical threshold for the column density of the population inversion is reached, at which point a strong level of coherence is established in the system and a powerful burst of radiation can ensue during the transient regime. This critical level also determines the spatial region where a transition from the unsaturated to the saturated maser regimes will take place; superradiance can thus be seen as the intermediary between the two. We also quantify the gain in radiation intensity attained during the superradiance phase relative to the two maser regimes and show how the strong coherence level during superradiance is well suited to explain observations that reveal intense and fast radiation flares in maser-hosting regions. [ABSTRACT FROM AUTHOR]

H 2 O maser emission associated with the massive star formation region W49N were observed with the Space-VLBI mission RadioAstron. The procedure for processing of the maser spectral line data obtained in the RadioAstron observations is described. Ultra-fine spatial structures in the maser emission were detected on space-ground baselines of up to 9.6 Earth diameters. The correlated flux densities of these features range from 0.1% to 0.6% of the total flux density. These low values of correlated flux density are probably due to turbulence either in the maser itself or in the interstellar medium. [ABSTRACT FROM AUTHOR]

A brief review of anomalous (paradoxical) results of measuring different parameters is presented in which the likely cause of the appearance of contradictions (oddities) is variations in space weather (solar activity). In physics, such artifacts are fictitious changes in the gravitational constant, the imitation of gravitational wave bursts by the Weber antennas, and false variations in the radioactive decay rate. In cosmophysics, these artifacts are apparent variations in the intensity of high-energy cosmic rays and in the solar neutrino flux. The brightest artifacts in astrophysics are the variability of the cosmological redshift, the presence of solar oscillations with a period of 160 min in the nuclei of distant galaxies, and the presence of periods of natural Earth oscillations in the radiation of cosmic masers. The influence of space weather in all these cases can be easily explained by assuming that there is an impact on the measurement technology, i.e., on the instruments. Space weather probably becomes an important factor in metrology. [ABSTRACT FROM AUTHOR]

Around 10 per cent of bright low-frequency radio sources observed with the Murchison Wide-field Array (MWA) show strong interplanetary scintillation (IPS) on time-scales of a few seconds, implying that almost all their low-frequency radio emission comes from a compact component less than 0.5 arcsec in angular size. Most of these objects are compact steep-spectrum or MHz-peaked spectrum radio sources. We have used mid-infrared data from the Wide-field Infrared Survey Explorer (WISE) catalogue to search for the host galaxies of 65 strongly scintillating MWA sources and compare their properties with those of the overall population of bright low-frequency radio sources. We identified WISE mid-infrared counterparts for 91 per cent of the bright sources in a single 900 deg2 MWA field, and found that the hosts of the strongly scintillating sources were typically at least 1 mag fainter in the WISE W1 (3.4  |${\mu}$| m) band than the hosts of weakly scintillating MWA sources of similar radio flux density. This difference arises mainly because the strongly scintillating sources are more distant. We estimate that strongly scintillating MWA sources have a median redshift of |$z$| ∼ 1.5, and that at least 30 per cent of them are likely to lie at |$z$| > 2. The recently developed wide-field IPS technique therefore has the potential to provide a powerful new tool for identifying high-redshift radio galaxies without the need for radio spectral-index selection. [ABSTRACT FROM AUTHOR]

The central molecular zone (CMZ) spans the inner ∼450 pc (∼3°) of our Galaxy. This region is defined by its enhanced molecular emission and contains 5 per cent of the entire Galaxy's molecular gas mass. However, the number of detected star-forming sites towards the CMZ may be low for the amount of molecular gas that is present, and improved surveys of star formation indicators can help clarify this. With the Karl G. Jansky Very Large Array (VLA), we conducted a blind survey of 6.7 GHz methanol (CH3OH) masers spanning the inner 3° × 40 arcmin (450 pc × 100 pc) of the Galaxy. We detected 43 CH3OH masers towards 28 locations, ∼16 of which are new detections. The velocities of most of these masers are consistent with being located within the CMZ. A majority of the detected CH3OH masers are distributed towards positive Galactic longitudes, similar to two-thirds of the molecular gas mass distributed at positive Galactic longitudes. The 6.7 GHz CH3OH maser is an exclusive indicator of high-mass (⁠|$\gt8\,{{M}_\odot}$|⁠) star formation, with new detections indicating sites of massive star formation in the CMZ. [ABSTRACT FROM AUTHOR]

We present the first broad-band X-ray study of the nuclei of 14 hard X-ray-selected giant radio galaxies, based both on the literature and on the analysis of archival X-ray data from NuSTAR, XMM–Newton, Swift, and INTEGRAL. The X-ray properties of the sources are consistent with an accretion-related X-ray emission, likely originating from an X-ray corona coupled to a radiatively efficient accretion flow. We find a correlation between the X-ray luminosity and the radio core luminosity, consistent with that expected for active galactic nuclei powered by efficient accretion. In most sources, the luminosity of the radio lobes and the estimated jet power are relatively low compared with the nuclear X-ray emission. This indicates that either the nucleus is more powerful than in the past, consistent with a restarting of the central engine, or that the giant lobes are dimmer due to expansion losses. [ABSTRACT FROM AUTHOR]

Laser induced fluorescence of microwave stimulated OH molecules from H[SUP2]O photodissociation is investigated as a first step in a series of laboratory experiments to understand features of astronomical OH masers. The inversion between the &PI;[SUB3/2], J = 7/2 Λ-doublet states of OH generated via photodissociation of cold H[SUP2]O at 157 nm is shown to be 1.8:1. Within a microwave, Fabry--Perot cavity tuned to the resonance of one of the main hyperfine transitions in this Λ doublet it is possible to stimulate all inverted OH molecules. The linewidth of the two main microwave transitions is measured as a function of the microwave power and interaction time. The results show that Doppler broadening is negligible at short interaction times of the molecules with the microwave field. [ABSTRACT FROM AUTHOR]

We have used the Australia Telescope Compact Array (ATCA) to conduct further observations of the 36.2-GHz (4−1 → 30E) methanol transition towards the nearby active galaxy NGC 4945. These observations have led to a more accurate determination of the offset between the maser emission and the nucleus of NGC 4945 with a typical synthesized beam of 6 arcsec × 4 arcsec (108 × 72 pc). This corresponds to a factor of 4 improvement with respect to the major axis of the beam. Other transitions of methanol and lines of other molecular species were obtained alongside the 36.2-GHz methanol emission, with strong detections of HC3N (J = 4 → 3) and CS (J = 1 → 0) presented here. We do not detect thermal methanol (5σ upper limit of 5 mJy in a 6 km s−1 channel) from the 48.4-GHz (10 → 00A+) ground-state transition, nor emission from the 44.1-GHz (70 → 61A+) class I maser transition (5σ upper limit of 6 mJy in a 3 km s−1 channel). We also present a comparison of the class I maser emission observed towards NGC 4945 with that from NGC 253 and towards the Galactic giant molecular cloud G 1.6-0.025. [ABSTRACT FROM AUTHOR]

We have used the Australia Telescope Compact Array (ATCA) to undertake the first high-angular-resolution observations of 37.7-GHz (7−2 → 8−1 E) methanol masers towards a sample of 11 high-mass star formation regions which host strong 6.7-GHz methanol masers. The 37.7-GHz methanol sites are coincident to within the astrometric uncertainty (0.4 arcsec) with the 6.7-GHz methanol masers associated with the same star formation region. However, spatial and spectral comparison of the 6.7- and 37.7-GHz maser emission within individual sources shows that the 37.7-GHz masers are less often, or to a lesser degree co-spatial than are the 12.2-GHz and 6.7-GHz masers. We also made sensitive, high-angular-resolution observations of the 38.3- and 38.5-GHz class II methanol transitions (62 → 53A− and 62 → 53A+, respectively) and the 36.2-GHz (4−1 → 30 E) class I methanol transition towards the same sample of 11 sources. The 37.7-, 38.3-, and 38.5-GHz methanol masers are unresolved in the current observations, which implies a lower limit on the brightness temperature of the strongest masers of more than 106 K. We detected the 38.3-GHz methanol transition towards seven sources, five of which are new detections and detected the 38.5-GHz transition towards six sources, four of which are new detections. We detected 36.2-GHz class I methanol masers towards all 11 sources, 6 of these are new detections for this transition, of which 4 sources do not have previously reported class I methanol masers from any transition. [ABSTRACT FROM AUTHOR]

The abundance of hydrogen sulfide, H2S, is underpredicted in standard astrophysical models and, thus, so are the effects of its rich chemistry. Its cation, H2S+, may have a similarly understated effect on the interstellar medium (ISM) but, unlike its neutral parent, its presence in the ISM is unconfirmed. Advancing the search for H2S+ requires the accurate characterization of its spectroscopic properties, both in the infrared (IR) and microwave regimes. Past spectroscopy experiments were unable to resolve its rotational structure to high accuracy and could not observe one of its fundamental vibrations. In this research, the H2S+ species has been studied at the highest available levels of electronic structure theory. Molecular structures, vibrational frequencies, rotational constants, and other rovibrational spectroscopic constants are predicted for H2S+ and eleven of its isotopologues. Previous ab initio studies fail to predict a separation of at least 5 cm−1 between the fundamental S−H stretching vibrations; a value equivalent to the uncertainty of previous photoelectron spectroscopy experiments. The characteristically different rotational properties of H2S and H2S+ are established concluding that most, if not all, large-dish telescopes and interferometers can easily discern the cation from the neutral. The best possible candidates for interstellar detection of H2S+ in the IR are determined to be the fundamental S−H stretches, due to their intensity and unique region in the IR. James Webb Space Telescope is best equipped for this search, whereas the Echelon-Cross-Echelle Spectrograph instrument on Stratospheric Observatory for Infrared Astronomy is better suited to find the bending fundamental of H2S+ and all fundamentals of its deuterated isotopologues. [ABSTRACT FROM AUTHOR]

Comprehensive rotation-vibration line lists are presented for the two main isotopologues of methyl chloride, 12CH335Cl and 12CH337Cl. The line lists, OYT-35 and OYT-37, are suitable for temperatures up to $$T=1200\,$$  K and consider transitions with rotational excitation up to J  = 85 in the wavenumber range 0 –  $$6400\,$$  cm−1 (wavelengths $$\lambda \gt 1.56\,\mu$$ m). Over 166 billion transitions among 10.2 million energy levels have been calculated variationally for each line list using a new empirically refined potential energy surface, determined by refining to 739 experimentally derived energy levels up to J  = 5, and an established ab initio dipole moment surface. The OYT line lists show excellent agreement with newly measured high-temperature infrared absorption cross-sections, reproducing both strong and weak intensity features across the spectrum. The line lists are available from the E xo M ol database and the cds database. [ABSTRACT FROM AUTHOR]

Context. High-mass young stellar objects (HMYSOs) can undergo accretion episodes that strongly affect the star evolution, the dynamics of the disk, and its chemical evolution. Recently reported extraordinary bursts in the methanol maser emission may be the observational signature of accretion events in deeply embedded HMYSOs. Aims. We analyze the light curve of 6.7 GHz methanol masers in S255IR-NIRS3 during the 2015–2016 burst. Methods. 8.5-yr monitoring data with an average sampling interval of 5 days were obtained with the Torun 32 m radio telescope. Archival data were added, extending the time series to ~27 yr. Results. The maser emission showed moderate (25–30%) variability on timescales of months to years over ~23 yr since its discovery. The main burst was preceded by a 1 yr increase of the total flux density by a factor of 2.5, then it grew by a factor of 10 over ~0.4 yr and declined by a factor of 8 during the consecutive 2.4 yr. The peak maser luminosity was a factor of 24.5 higher than the pre-burst quiescent value. The light curves of individual features showed considerable diversity but indicated a general trend of suppression of the maser emission at blueshifted (<4.7 km s−1) velocities when the redshifted emission rapidly grew and new emission features appeared at velocities >5.8 km s−1. This new emission provided a contribution of about 80% to the maser luminosity around the peak of the burst. The duration of the burst at the extreme redshifted velocities of 7.1–8.7 km s−1 was from 0.9 to 1.9 yr, and its lower limit for the other features was ~3.9 yr. Conclusions. The onset of the maser burst exactly coincides with that of the infrared burst estimated from the motion of the light echo. This strongly supports the radiative pumping scheme of the maser transition. The growth of the maser luminosity is the result of an increasing volume of gas where the maser inversion is achieved. [ABSTRACT FROM AUTHOR]

The results of a study of H2O and OH maser emission in the complex region of active star formation W75 N are presented. Observations were obtained using the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia) and the Nan3ay radio telescope (France). Flaring H2O maser features may be identified with maser spots associated with the sources VLA 1 and VLA 2. Themain H2O flares occurred in VLA 1. The flare emission was associated with either maser clusters having closely spaced radial velocities and sizes up to ~2 AU or individual features. The maser emission is generated in a medium where turbulence on various scales is present. Analysis of the line shapes during flare maxima does not indicate the presence of the simplest structures—homogeneous maser condensations. Strong variability of the OH maser emission was observed. Zeeman splitting of the 1665-MHz line was detected for several features of the same cluster at a radial velocity of +5.5 km/s. The mean line-of-sight magnetic field in this cluster is ~0.5 mG, directed away from the observer. Flares of the OH masers may be due to gas compression at a shock or MHD wave front. [ABSTRACT FROM AUTHOR]

Today's crisis of education should be considered as a crisis of a moral and spiritual basis of our society. Upbringing and education are a kind of spiritual activity, an important component of spiritual culture. Thanks to upbringing and education, a person improves himself intellectually, mentally, morally, artistically, aesthetically, spiritually, acquires the image of the Man of Culture. The crisis of the educational system is an integral part of the global spiritual crisis that has embraced society. Pedagogical science needs now a careful study of the multidimensionality and multiplicity of a person, the understanding of its true essence on the basis of a new methodology of knowledge of a unified and holistic world. [ABSTRACT FROM AUTHOR]

Context. HCN is a major constituent of the circumstellar envelopes of carbon-rich evolved stars, and rotational lines from within its vibrationally excited states probe parts of these regions closest to the stellar surface. A number of such lines are known to show maser action. Historically, in one of them, the 177 GHz J = 2 → 1 line in the l-doubled bending mode has been found to show relatively strong maser action, with results only published for a single object, the archetypical high-mass loss asymptotic giant branch (AGB) star IRC+10216. Aims. To examine how common 177 GHz HCN maser emission is, we conducted an exploratory survey for this line toward a select sample of carbon-rich asymptotic giant branch stars that are observable from the southern hemisphere. Methods. We used the Atacama Pathfinder Experiment 12 meter submillimeter Telescope (APEX) equipped with a new receiver to simultaneously observe three J = 2 → 1 HCN rotational transitions, the (0; 11c ; 0) and (0; 11d ; 0) l-doublet components, and the line from the (0, 0, 0) ground state. Results. The (0; 11c ; 0) maser line is detected toward 11 of 13 observed sources, which all show emission in the (0, 0, 0) transition. In most of the sources, the peak intensity of the (0; 11c ; 0) line rivals that of the (0, 0, 0) line; in two sources, it is even stronger. Except for the object with the highest mass-loss rate, IRC+10216, the (0; 11c ; 0) line covers a smaller velocity range than the (0, 0, 0) line. The (0; 11d ; 0) line, which is detected in four of the sources, is much weaker than the other two lines and covers a velocity range that is smaller yet, again except for IRC+10216. Compared to its first detection in 1989, the profile of the (0; 11c ; 0) line observed toward IRC+10216 looks very different, and we also appear to see variability in the (0, 0, 0) line profile (at a much lower degree). Our limited information on temporal variabilitydisfavors a strong correlation of maser and stellar continuum flux. Conclusions. Maser emission in the 177 GHz J = 2 → 1 (0; 11c ; 0) line of HCN appears to be common in carbon-rich AGB stars. Like for other vibrationally excited HCN lines, our observations indicate that the origin of these lines is in the acceleration zone of the stellar outflow in which dust is forming. For all the stars toward which we detect the maser line, the number of photons available at 7 and 14 μm, corresponding to transitions to vibrationally excited states possibly involved in its pumping, is found to be far greater than that of the maser photons, which makes radiative pumping feasible. Other findings point to a collisional pumping scheme, however. [ABSTRACT FROM AUTHOR]

The X-ray spectra of intermediate polars can be modelled to give a direct measurement of white dwarf mass. Here, we fit accretion column models to NuSTAR spectra of three intermediate polars; V709 Cas, NYLup, and V1223 Sgr in order to determine their masses. From fits to 3-78 keV spectra, we find masses of MWD = 0.88+0.05 -0.04M⊙, 1.16+0.04 -0.02M⊙, and 0.75 ± 0.02M⊙ for V709 Cas, NYLup, and V1223 Sgr, respectively. Our measurements are generally in agreement with those determined by previous surveys of intermediate polars, but with typically a factor ~2 smaller uncertainties. This work paves the way for an approved NuSTAR Legacy Survey of white dwarf masses in intermediate polars. [ABSTRACT FROM AUTHOR]

We develop a data-driven spectral model for identifying and characterizing spatially unresolved multiple-star systems and apply it to APOGEE DR13 spectra of main-sequence stars. Binaries and triples are identified as targets whose spectra can be significantly better fit by a superposition of two or three model spectra, drawn from the same isochrone, than any singlestar model. From an initial sample of ~20 000 main-sequence targets, we identify ~2500 binaries in which both the primary and secondary stars contribute detectably to the spectrum, simultaneously fitting for the velocities and stellar parameters of both components. We additionally identify and fit ~200 triple systems, as well as ~700 velocity-variable systems in which the secondary does not contribute detectably to the spectrum. Our model simplifies the process of simultaneously fitting single- or multi-epoch spectra with composite models and does not depend on a velocity offset between the two components of a binary, making it sensitive to traditionally undetectable systems with periods of hundreds or thousands of years. In agreement with conventional expectations, almost all the spectrally identified binaries with measured parallaxes fall above the main sequence in the colour-magnitude diagram. We find excellent agreement between spectrally and dynamically inferred mass ratios for the ~600 binaries in which a dynamical mass ratio can be measured from multi-epoch radial velocities. We obtain full orbital solutions for 64 systems, including 14 close binaries within hierarchical triples. We make available catalogues of stellar parameters, abundances, mass ratios, and orbital parameters. [ABSTRACT FROM AUTHOR]

We report on the astrometric registration of very long baseline interferometry images of the SiO and H2O masers in OH231.8+4.2, the iconic proto-planetary nebula also known as the Calabash nebula, using the Korean VLBI Network and source frequency phase referencing. This, for the first time, robustly confirms the alignment of the SiO masers, close to the asymptotic giant branch star, driving the bilobe structure with the water masers in the outflow. We are able to trace the bulk motions for the H2O masers over the last few decades to be 19 km s-1 and deduce that the age of this expansion stage is 38±2 yr. The combination of this result with the distance allows a full 3D reconstruction and confirms that the H2O masers lie on and expand along the known large-scale symmetry axis and that the outflow is only a few decades old, so mass loss is almost certainly ongoing. Therefore, we conclude that the SiO emission marks the stellar core of the nebular, the H²O emission traces the expansion, and there must be multiple epochs of ejection to drive the macro-scale structure. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs), characterized by strong bursts of radiation intensity at radio wavelengths lasting on the order of a millisecond, have yet to be firmly associated with a family, or families, of astronomical sources. It follows that despite the large number of proposed models, no well-defined physical process has been identified to explain this phenomenon. In this paper, we demonstrate how Dicke's superradiance, for which evidence has recently been found in the interstellar medium, can account for the characteristics associated with FRBs. Our analysis and modelling of previously detected FRBs suggest they could originate from regions in many ways similar to those known to harbour masers or megamasers, and result from the coherent radiation emanating from populations of molecules associated with large-scale entangled quantum mechanical states. We estimate this entanglement to involve as many as ∼1030 to ∼1032 molecules over distances spanning 100-1000 au.. [ABSTRACT FROM AUTHOR]