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When observing the Sun with RATAN-600 radio telescope using a spectropolarimetric complex in the range 1–3 GHz, as well as when observing coronal rain, absorption in the radio emission was discovered in the spectral region 1.5–1.65 GHz in active solar regions located under a cold filament or on the limb under a prominence. The observed line structure corresponds to the hyperfine splitting frequencies in the ground state of X²Π₃/₂ hydroxyl (OH) 1612–1720 MHz. When the observed active region passes through the knife-shaped beam pattern of the telescope antenna, the absorption band shifts in frequency due to a shift in the energy levels of the OH molecule in a magnetic field, which changes along the filament.

The absorption spectrum of H219O, a radioactive isotopologue of the water molecule, is predicted using variational nuclear motion calculated based on a high precision potential energy function and ab initio dipole moment surface. Vibrational - rotational energy levels and wave functions, line centers and Einstein coefficients for dipole transitions are calculated. Predicted transition wavenumbers are improved by extrapolating known empirical energy levels of the stable H216O, H217O and H218O isotopologues to H219O. A line list for possible atmospheric application is presented which includes air line broadening coefficients. The calculations span a wide spectral range covering infrared and visible wavelengths, and are appropriate for temperatures up to 1000 K. Windows suitable for observing absorption by H219O are identified and comparisons made with the infrared spectra of water vapor in natural abundance, H215O and H214O. [ABSTRACT FROM AUTHOR]

The predicted rotation-vibration absorption spectrum of the radioactive isotopically substituted water molecule, H214O, is presented. Variational nuclear-motion calculations are performed using the DVR3D software package based on the use of a high-precision potential energy function and an accurate dipole moment surface. Line centres, intensity and Einstein coefficients are calculated, and air pressure broadening coefficients are estimated. The calculation was carried out over a wide wavenumber range from 0 to 25000 cm $ {}^{-1} $ − 1 and total angular momentum up to J = 20. Isotopologue extrapolation rules based on experimental data on the energy levels of the stable isotopologues H216O, H $ {}_{2}^{16} $ 2 16 O H217O and H218O were also used to improve the predicted line positions. Spectral ranges best suited to the detection of H214O are identified. [ABSTRACT FROM AUTHOR]

Atmospheric solar spectra in the absorption lines of methane in the near-IR range are modeled and compared using spectra measured on a ground-based Fourier transform spectrometer with high spectral resolution under different atmospheric conditions. The content of methane in the atmospheric column is retrieved using different versions of spectroscopic databases HITRAN (2008, 2012, 2016, 2020), GEISA (2015, 2020), and ATM (2016, 2020) and the CH4 line list GOSAT2014. The RMS value averaged over 1346 spectra (the deviation of the calculated spectra from ones measured) is calculated for each spectroscopic base. The lowest RMS value is observed for results obtained with CH4 absorption lines from ATM2020, ATM2016, and HITRAN2008. Parameters of the CH4 absorption lines that introduce the greatest error into modeling radiative transfer in the atmosphere are revealed in the spectral range of 6000–6100 cm–1. [ABSTRACT FROM AUTHOR]

Simultaneous multi-band very long baseline interferometry (VLBI) observations at millimeter wavelengths have huge potential for various science cases. However, there exist difficulties in expanding the scientific targets, as the sensitivity of radio telescopes at millimeter wavelengths is typically lower compared to that at centimeter wavelengths. In order to realize high-sensitivity mm-VLBI observations in the East Asia region, we are promoting the HINOTORI (Hybrid Installation project in NObeyama, Triple-band ORIented) project, which aims to launch the wide-band and simultaneous triple-band (22/43/86 GHz) VLBI system with the Nobeyama 45 m Radio Telescope (NRO45). The simultaneous 22/43 GHz observation mode has already been operated for the open-use program. We have recently completed the performance evaluation of the receiver and observing system at 86 GHz. In addition, a new wide-band VLBI back-end system has been installed on the NRO45 and the performance of this receiving system has been found to be sufficient to meet scientific requirements. Currently, we are performing commissioning observations to establish regular VLBI operation with simultaneous triple-band mode together with the Korean VLBI Network. The participation of the NRO45 is expected to strengthen the mm-VLBI observation network in the East Asia region and to be a very powerful addition with respect to the science of of black hole jets. [ABSTRACT FROM AUTHOR]

Simultaneous multi-band very long baseline interferometry (VLBI) observations at millimeter wavelengths have huge potential for various science cases. However, there exist difficulties in expanding the scientific targets, as the sensitivity of radio telescopes at millimeter wavelengths is typically lower compared to that at centimeter wavelengths. In order to realize high-sensitivity mm-VLBI observations in the East Asia region, we are promoting the HINOTORI (Hybrid Installation project in NObeyama, Triple-band ORIented) project, which aims to launch the wide-band and simultaneous triple-band (22/43/86 GHz) VLBI system with the Nobeyama 45 m Radio Telescope (NRO45). The simultaneous 22/43 GHz observation mode has already been operated for the open-use program. We have recently completed the performance evaluation of the receiver and observing system at 86 GHz. In addition, a new wide-band VLBI back-end system has been installed on the NRO45 and the performance of this receiving system has been found to be sufficient to meet scientific requirements. Currently, we are performing commissioning observations to establish regular VLBI operation with simultaneous triple-band mode together with the Korean VLBI Network. The participation of the NRO45 is expected to strengthen the mm-VLBI observation network in the East Asia region and to be a very powerful addition with respect to the science of of black hole jets.

The POKAZATEL line list is currently the most complete theoretical list of H2O monomer absorption lines. It contains H2O lines up to the dissociation energy ∼40 000 cm−1 (0.25 μm). The atmospheric transmission of ultraviolet (UV) radiation is simulated with the use of H2O lines from POKAZATEL. The broadening parameters of absorption lines in the UV region are determined more accurately with the use of different approximations. It is shown that the contribution of H2O absorption lines to the atmospheric transmission can attain 0.03 near 25 000 cm−1 at a spectral resolution of 0.01 cm−1. [ABSTRACT FROM AUTHOR]

A room temperature line list for the H 2 15O radioactive isotopologue of the water molecule is computed using the variational nuclear-motion DVR3D program suite and an empirical high-precision potential energy function. The line list consists of rotation-vibrational energies and Einstein-A coefficients, covering a wide spectral range from 0 to 25000 cm − 1 and the total angular momenta J up to 30. Estimates of air-broadening coefficients are provided. Experimentally derived energies of H 2 16 O, H 2 17 O and H 2 18 O from the literature are used to provide improved energies for important states with uncertainty estimates for the H 2 15O. A number of the wmost promising spectroscopic ranges for the detection of H 2 15O are proposed. The calculated absorption spectrum should be useful for the study gaseous radioactive water at IR region, determining concentration, etc. [ABSTRACT FROM AUTHOR]

Detections of deuterium in high-redshift Lyman limit absorption systems along the line of sight to QSOs promise to reveal the primordial deuterium abundance. At present, the deuterium abundances (D/H) derived from the very few systems observed are significantly discordant. Assuming the validity of all the data, if this discordance does not reflect intrinsic primordial inhomogeneity, then it must arise from processes operating after the primordial nucleosynthesis epoch. We consider processes that might lead to significant deuterium production or destruction and yet allow the cloud to mimic a chemically unevolved system. These processes include, for example, anomalous/stochastic chemical evolution and D/4He photodestruction. In general, we find it unlikely that these processes could have significantly altered D/H in Lyman limit clouds. We argue that chemical evolution scenarios, unless very finely tuned, cannot account for significant local deuterium depletion since they tend to overproduce 12C, even when allowance is made for possible outflow. Similarly, D/4He photodestruction schemes engineered to locally produce or destroy deuterium founder on the necessity of requiring an improbably large γ-ray source density. Future observations of D/H in Lyman limit systems may provide important insight into the initial conditions for the primordial nucleosynthesis process, early chemical evolution, and the galaxy formation process. © 1997. The American Astronomical Society. All rights reserved.

We report on the first implementation of a terahertz (THz) source based on a Josephson flux-flow oscillator (FFO) that radiates to open space. The excellent performance of this source and its maturity for practical applications has been demonstrated by the spectroscopy of gas absorption. To study the radiated power, we used a bolometric detection method and additionally calibrated the power by means of pumping the superconductor–insulator–superconductor (SIS) junction, integrated on a single chip with the FFO. For calibration, we developed a program using the SIS-detected power calculations in accordance with the Tien and Gordon model. The power emitted to open space is estimated to be from fractions of µW to several µW in the wide region from 0.25 THz up to 0.75 THz for different designs, with a maximum power of 3.3 µW at 0.34 THz. Next, we used a gas cell and a heterodyne superconducting integrated receiver to trace the absorption lines of water and ammonia with a spectral resolution better than 100 kHz. Our experiment for gas absorption is the first demonstration of the applicability of the FFO as an external active source for different tasks, such as THz spectroscopy, near-field THz imaging and microscopy.

The determination of fundamental parameters in low-mass X-ray binaries (LMXBs) typically relies on measuring the radial velocity curve of the companion star through optical or near-infrared spectroscopy. It was recently suggested that high resolution X-ray spectroscopy might enable a measurement of the radial velocity curve of the compact object by monitoring the Doppler shifts induced by the orbital motion of the disc wind or the disc atmosphere. We analysed a Chandra -HETG+ NuSTAR soft state observation of MXB 1659-298, an eclipsing neutron star LMXB. We measured a radial velocity curve whose phase offset and semi-amplitude are consistent with the primary star. We derived the value for the semi-amplitude of the radial velocity for the compact object K 1 = 89 ± 19 km s−1, constrained the mass of the secondary (0.3 M⊙ ≤ M 2 ≤ 0.8 M⊙) and the orbital inclination of the binary system (73°≤ i ≤77°). These values are consistent with previous estimates from independent methods. Via the same technique, the next generation of X-ray observatories equipped with high spectral resolution instruments (e.g. Athena) will have the potential to measure the radial velocity curve of the primary in high inclination X-ray binaries to an accuracy of a few per cent. [ABSTRACT FROM AUTHOR]

We present twomeasurements of the temperature-density relationship (TDR) of the intergalactic medium (IGM) in the redshift range 2.55 < z < 2.95 using a sample of 13 high-quality quasar spectra and high resolution numerical simulations of the IGM. Our approach is based on fitting the neutral hydrogen column density NHI and the Doppler parameter b of the absorption lines in the Lyα forest. The first measurement is obtained using a novel Bayesian scheme that takes into account the statistical correlations between the parameters characterizing the lower cut-off of the b-NHI distribution and the power-law parameters T0 and γ describing the TDR. This approach yields T0/103 K = 15.6 ± 4.4 and γ = 1.45 ± 0.17 independent of the assumed pressure smoothing of the small-scale density field. In order to explore the information contained in the overall b-NHI distribution rather than only the lower cut-off, we obtain a second measurement based on a similar Bayesian analysis of the median Doppler parameter for separate column-density ranges of the absorbers. In this case, we obtain T0/103 K = 14.6 ± 3.7 and γ = 1.37 ± 0.17 in good agreement with the first measurement. Our Bayesian analysis reveals strong anticorrelations between the inferred T0 and γ for both methods as well as an anticorrelation of the inferred T0 and the pressure smoothing length for the second method, suggesting that the measurement accuracy can in the latter case be substantially increased if independent constraints on the smoothing are obtained. Our results are in good agreement with other recent measurements of the thermal state of the IGM probing similar (over-)density ranges. [ABSTRACT FROM AUTHOR]

AX J1745.6-2901 is a high-inclination (eclipsing) transient neutron star (NS) low-mass X-ray binary showcasing intense ionized Fe K absorption. We present here the analysis of 11 XMM-Newton and 15 NuSTAR new data sets (obtained between 2013 and 2016), therefore tripling the number of observations of AX J1745.6-2901 in outburst. Thanks to simultaneous XMM-Newton and NuSTAR spectra, we greatly improve on the fitting of the X-ray continuum. During the soft state, the emission can be described by a disc blackbody (kT∼1.1-1.2 keV and inner disc radius rDBB ∼ 14 km), plus hot (kT ∼ 2.2-3.0 keV) blackbody radiation with a small emitting radius (rBB ∼ 0.5 - 0.8 km) likely associated with the boundary layer or NS surface, plus a faint Comptonization component. Imprinted on the spectra are clear absorption features created by both neutral and ionized matter. Additionally, positive residuals suggestive of an emission Fe Kα disc line and consistent with relativistic ionized reflection are present during the soft state, while such residuals are not significant during the hard state. The hard-state spectra are characterized by a hard (Γ ∼ 1.9-2.1) power law, showing no evidence for a high energy cut-off (kTe > 60-140 keV) and implying a small optical depth (τ < 1.6). The new observations confirm the previously witnessed trend of exhibiting strong Fe K absorption in the soft state that significantly weakens during the hard state. Optical (GROND) and radio (GMRT) observations suggest for AX J1745.6-2901 a standard broad-band spectral energy distribution as typically observed in accreting NSs. [ABSTRACT FROM AUTHOR]

We report the discovery and analysis of the most metal-poor damped Lyman a (DLA) system currently known, based on observations made with the Keck HIRES spectrograph. The metal paucity of this system has only permitted the determination of three element abundances: [C/H] = -3.43 ± 0.06, [O/H] = -3.05 ± 0.05 and [Si/H] = -3.21 ± 0.05, as well as an upper limit on the abundance of iron: [Fe/H] ≤ -2.81. This DLA is among the most carbon-poor environment currently known with detectable metals. By comparing the abundance pattern of this DLA to detailed models of metal-free nucleosynthesis, we find that the chemistry of the gas is consistent with the yields of a 20.5 Mʘ metal-free star that ended its life as a core-collapse supernova; the abundances we measure are inconsistent with the yields of pair- instability supernovae. Such a tight constraint on the mass of the progenitor Population III star is afforded by the well-determined C/O ratio, which we show depends almost monotonically on theprogenitormass when the kinetic energy of the supernova explosion is Eexp ≳ 1.5 x 1051 erg. We find that the DLA presented here has just crossed the critical 'transition discriminant' threshold, rendering the DLA gas now suitable for low mass star formation. We also discuss the chemistry of this system in the context of recent models that suggest some of the most metal-poor DLAs are the precursors of the 'first galaxies', and are the antecedents of the ultrafaint dwarf galaxies. [ABSTRACT FROM AUTHOR]

Ne VIII absorbers seen in QSO spectra are useful tracers of warm ionized gas, when collisional ionization is the dominant ionization process. While photoionization by the ultraviolet background (UVB) is a viable option, it tends to predict large line-of-sight thickness for the absorbing gas. Here, we study the implications of the recently updated UVB at low z to understand the ionization mechanisms of intervening Ne VIII absorbers. With the updated UVB, one typically needs higher density and metallicity to reproduce the observed ionic column densities under photoionization. Both reduce the inferred line-of-sight thicknesses of the absorbers. We find a critical density of ≥5 × 10-5 cm-3 above which the observed N(Ne VIII)/N(O VI) can be reproduced by pure collisional processes. If the gas is of near solar metallicity (as measured for the low ions) then the cooling time-scales will be small (<108 yrs). Therefore, a continuous injection of heat is required in order to enhance the detectability of the collisionally ionized gas. Using photoionization models we find that in almost all Ne VIII systems the inferred low ion metallicity is near solar or supersolar. If we assume the Ne VIII phase to have similar metallicities then photoionization can reproduce the observed N(Ne VIII)/N(O VI) without the line-of-sight thickness being unreasonably large and avoids cooling issues related to the collisional ionization at these metallicities. However, the indication of broad Lyα absorption in a couple of systems, if true, suggests that the Ne VIII phase is distinct from the low ion phase having much lower metallicity. [ABSTRACT FROM AUTHOR]

We present the results from our search for H I 21-cm absorption in a sample of 16 strong Fe II systems [Wr(Mg II λ2796) ≥ 1.0 Å and Wr(Fe II λ2600) or WFeII ≥ 1 Å] at 0.5 < z < 1.5 using the Giant Metrewave Radio Telescope and the Green Bank Telescope. We report six new H I 21-cm absorption detections from our sample, which have increased the known number of detections in strong Mg II systems at this redshift range by ~50 per cent. Combining our measurements with those in the literature, we find that the detection rate of H I 21-cm absorption increases with,WFeII, being four times higher in systems with WFeII ≥ 1 Å compared to systems with WFeII < 1 Å. The N(HI) associated with the H I 21-cm absorbers would be ≥2 x 1020 cm-2, assuming a spin temperature of ~500 K (based on H I 21-cm absorption measurements of damped Lyman α systems at this redshift range) and unit covering factor. We find that H I 21-cm absorption arises on an average in systems with stronger metal absorption. We also find that quasars with H I 21-cm absorption detected towards them have systematically higher E(B - V) values than those which do not. Further, by comparing the velocity widths of H I 21-cm absorption lines detected in absorption- and galaxy-selected samples, we find that they show an increasing trend (significant at 3.8σ) with redshift at z < 3.5, which could imply that the absorption originates from more massive galaxy haloes at high z. Increasing the number of H I 21-cm absorption detections at these redshifts is important to confirm various trends noted here with higher statistical significance. [ABSTRACT FROM AUTHOR]

In this article, we first review the past decade of efforts in detecting the missing baryons in the warm hot intergalactic medium and summarize the current state of the art by updating the baryon census and physical state of the detected baryons in the local Universe. We then describe observational strategies that should enable a significant step forward in the next decade, while waiting for the step-up in quality offered by future missions. In particular, we design a multi-megasecond and multiple cycle XMM-Newton legacy' program (which we name the Ultimate Roaming Baryon Exploration, or URBE), aimed at securing detections of the peaks in the density distribution of the Universe of missing baryons over their entire predicted range of temperatures. [ABSTRACT FROM AUTHOR]

Spectrum research of degraded DNA of herring in the range 0.1-1 THz was done. DNA native absorption lines were obtained. Lines, responsible for interaction with water and conformational changes, were identified.

Most of the Broad Absorption Lines (BALs) in quasars show very complex profiles. An idea to explain these profiles is that the dynamical systems of broad line regions are not homogeneous but consist of a number of dense regions or ion populations with different physical parameters. This approach is used to study the ultraviolet CIV resonance lines in the spectra of a group of high ionization BAL quasars, using the Gauss-Rotation model.

We investigate the influence of the sea surface temperature (SST) changes on the middle atmosphere of a tidally locked Earth-like planet orbiting a G star using the coupled 3D chemistry-climate model CESM1(WACCM). We perform three 90 day simulations. The first simulation is a present-day Earth (PDE) simulation, the second is a simulation of a tidally locked Earth-like planet with a tidally locked aquaplanet sea surface temperature (cold TLE (CLTE)) and the third is a hybrid simulation of a tidally locked Earth-like planet with a present-day Earth sea surface temperature (warm TLE (WTLE)). Our results show that changes in the SST have an influence on the lower stratospheric temperature and the secondary ozone layer. Both atmospheres exhibit a dayside upwelling and a nightside downwelling extending from the surface to the mesosphere. They are also characterised by comparable lower and middle stratospheric horizontal winds and relatively different mesospheric horizontal winds. The temperature of the WTLE atmosphere is altered as a result of the SST changes, compared to the CTLE. Specifically, the WTLE lower tropospheric temperature is increased by 3.7 K on average, due to the absorption of the increased upwelling longwave radiation and the increased sensible and latent heat. The WTLE upper troposphere temperature is decreased by 4 K on average, is adiabatic in nature, and is generated by the increased WTLE upwelling. The WLTE lower stratospheric temperature is increased by 3.8 K on average due to the absorption of the increased upwelling longwave radiation. The lower mesospheric temperature is decreased by 1.13 K on average due to increased mesospheric wave breaking. The upper mesospheric temperature is increased by 4.3 K, and its generation mechanism is currently unknown. Furthermore, the secondary ozone volume mixing ratio is increased by 40.5 %. The occurrence of large-scale vortices and variable jet streams depends, to some extent, on the SST distribution. [ABSTRACT FROM AUTHOR]

Broad Absorption Line QSOs (BALQSOs) are a subtype of radio-quite QSOs that exhibit complex and unusually broad (FWHM ⩾ 2,000 km/s) absorption lines. The existence of these lines in BALQSO spectra raises some questions with respect to the properties, the physical conditions and kinematics of the BAL material as well as the morphology of BAL troughs. In this study, taking into consideration the clumpy structure of the AGN outflow winds, we propose a physical model in order to explain the formation of BAL troughs and we give the mathematical description of this model. We also propose a method for analyzing spectroscopically the BAL profiles in the UV region of the electromagnetic spectrum. This method consists of the criteria we set during the fitting process of BAL troughs. The purpose of these criteria is to enable us to determine the exact number of components needed to simulate accurately the BAL troughs and guarantee the uniqueness of the fit.We give an application of the model and the method for Si IV and C IV resonance lines in the case of two BALQSOs. From the analysis, we conclude that the BAL material is in the form of clouds (density enhancements) that move radially and intercept the line-of-sight to the central continuum source. Using our method, we find the number of absorption components needed to simulate the BAL profiles, which means the number of clouds in the line-of-sight. We calculate the velocity shifts, the FWHM and the optical depths of the absorption components of BALs and we propose an internal structure for these clouds. Finally, we give some correlations between the properties of absorption components of Si IV and C IV. [ABSTRACT FROM AUTHOR]

We map out calcium II and sodium I absorption (Fraunhofer H, K & D lines) induced by both the interstellar medium and the circumgalactic medium of the Milky Way. Our measurements cover more than 9000 deg² and make use of about 300 000 extragalactic spectra from the Sloan Digital Sky Survey.We present absorption maps for these two species and then compare their distributions to those of neutral hydrogen and dust. We show that the abundance of Na I with respect to neutral hydrogen stays roughly constant in different environments, while that of Ca II decreases with hydrogen column density. Studying how these tracers vary as a function of velocity, we show that, on average, the NNaI/NCa II ratio decreases at higher velocity with respect to the local standard of rest, similar to the local Routly-Spitzer effect but seen on Galactic scale. We show that it is likely caused by higher gas/dust density at lower velocity. Finally, we show that Galactic Ca II and Na I absorption needs to be taken into account for precision photometry and, more importantly, for photometric redshift estimation with star-forming galaxies. Our maps of Ca II and Na I absorption are publicly available. [ABSTRACT FROM AUTHOR]

Absolute single-photoionization cross sections for aluminum-like P 2+ have been measured from 26.5 to 66.5 eV using photoion yield spectroscopy. In addition, absolute cross section measurements for the single-photoionization of magnesium-like P 3+ have been measured from 43 to 60 eV. For both ions, the measured spectra are dominated by Rydberg series resonances superimposed on a non-resonant direct photoionization cross section. Analyses of these data have helped identify the initial and final states of the Rydberg series observed in each photoion. In addition, quantum defects are derived for each series. [ABSTRACT FROM AUTHOR]

The photoionization of Cl + leading to Cl 2+ was measured in the photon energy range of 19.5–28.0 eV. A spectrum with a photon energy resolution of 15 meV normalized to absolute cross-section measurements is presented. The measurements were carried out by merging a Cl + ion beam with a photon beam of highly monochromatic synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory. The measured photoionization of Cl + consists of several autoionization resonances surperimposed on the direct photoionization signal. Most of the prominent resonances are assigned to members of Rydberg series originating from the singlet ground state and from metastable triplet levels within the ground-state configuration of Cl + . The direct ionization cross section is no larger than 12 Mb. [ABSTRACT FROM AUTHOR]