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Chromospherically active binaries’ (CABs) are late-type evolved stars with strong chromosphere/coronae and high flare activity levels. Starspot evolution in these CABs and binaries reveals strong stellar and chromospheric activities. In binaries, the tidal interaction via the internal dynamo motion, during rapid rotation of the component stars generates magnetic fields. The magnetic activity heats the tenuous coronal plasma, and the reconnection of energetic particles leads to stellar flare formation. Cyclic-variation signatures in brightness and emission lines are indicators of coronal/chromospheric activities. The spatial population densities of CABs are large, and their hard energy spectral characteristics are prominent in our galaxy. Photo-ionization/collisional excitation processes in the coronae of CABs generate a strong thermal emission line at 6.7 keV. In the present work, we re-analyzed stellar flare data of two CABs (Algol & GT Muscae) observed with Suzaku. We resolved the 6.7 keV emission spectrum and equivalent width (EW) in each source’s stellar flare data. The resolved energy spectra are remarkably similar to that of the hard energy spectra at 6.7 keV of X-ray point sources observed in different Galactic regions. The EW of the 6.7 keV emission line obtained in this work compares favorably with the EW range (260 eV – 980 eV) of the 6.7 keV energy spectra of Galactic point sources. Hence, cumulative X-ray emission lines of coronal plasma (and their EWs) emitted by numerous point sources in different Galactic plane positions give clues on the Galactic Ridge X-ray Emission (GRXE) mechanism. We are of the view that CABs could account for a large number of fast-transient X-ray sources that emit thermal emission line at 6.7 keV during their quiescent and flared phases, and these underlying population sources could contribute significantly to the total luminosity of 6.7 keV GRXE.

InyAl1−yN epifilms with alloy compositions (y) ranging from 0.13 to 0.47 were grown on a GaN template using a low-temperature molecular-beam-epitaxy technique. Because of the larger lattice constant of high-indium-content InyAl1−yN epifilm, the compressive stress accumulated during epitaxy. When the compressive stress exceeded the elastic limit of the InyAl1−yN epifilms, a “concave-valley” crack with an equivalent width (~25 nm) was generated to form a prismatic domain. Our calculation and fitting results showed that no cracking occurred when the lattice mismatch was 2.4% because the stress exceeded the elastic limit.

We analyse the spectroscopic and photometric variability of the Oe star HD 60848 over the last twenty five years. The spectra reveal recurrent, but irregular cycles of increased circumstellar emission lines. These cycles are highly asymmetric displaying a slow increase over about 6 years, followed by a fast decay within about 6 months. Our analysis focuses on the most recent cycle (2013 - 2020). The equivalent width and velocity separation of the emission peaks indicate variations of the outer disk radius by a factor ~ 2.2, although the variability appears more complex than expected from first principle relations for optically thin Keplerian disks. We observe a time delay between the variations of the strengths of He I 5876 on the one hand and H-alpha and H-beta on the other hand. We interpret this behaviour in a two-step disk growth scenario, where the disk first expands radially before its density increases. A difference in behaviour is also seen between H-alpha and the H I Paschen lines, with the latter displaying a more symmetric cycle, similar to the photometric variability. The rather fast decays of the H-alpha emission observed in 2001, 2009 and 2018 - 2019 suggest that the strong radiation field and early spectral type of the star lead to a faster dissipation of the disk than in later-type Be stars, as theoretically expected. We discuss X-ray observations of the star both during a high and a low-emission state. The X-ray spectrum is soft at both epochs, and the X-ray fluxes are only marginally different and remain consistent with the canonical Lx/Lbol relation of O-type stars. These results indicate that the circumstellar decretion disk of HD 60848 has essentially no impact on the star's X-ray emission, and that the latter most likely arises inside the stellar wind., Comment: New Astronomy, accepted

The first non-vanishing term in the perturbation expansion of the electron contribution to the line width, commonly used in spectral line broadening by plasmas, was previously expressed in terms of the thermally averaged bremsstrahlung Gaunt factor. The approximations in the derivation, however, suggest that the result is uncertain. The electron width formula is tested with the hydrogen Balmer series and found suspect. Calculations for the He II Lyman series also display similar difficulties. The limitation of this electron width formulation is traced to the absence of an explicit strong collision cutoff beyond which the second-order theory is invalid.

Six asteroids including two NEAs, one of which is PHA, accessible for observation in September 2012 were investigated using a low-resolution (R ≈ 100) spectrophotometry in the range 0.35–0.90 μm with the aim to study features of their reflectance spectra. A high-altitude position of our Terskol Observatory (3150 m above sea level) favorable for the near-UV and visible-range observations of celestial objects allowed us to probably detect some new spectral features of the asteroids. Two subtle absorption bands centered at 0.53 and 0.74 μm were found in the reflectance spectra of S-type (32) Pomona and interpreted as signs of presence of pyroxenes in the asteroid surface matter and its different oxidation. Very similar absorption bands centered at 0.38, 0.44 and 0.67–0.71 μm have been registered in the reflectance spectra of (145) Adeona, (704) Interamnia, and (779) Nina of primitive types. We performed laboratory investigations of ground samples of known carbonaceous chondrites, Orguel (CI), Mighei (CM2), Murchison (CM2), Boriskino (CM2), and seven samples of low-iron Mg serpentines as possible analogs of the primitive asteroids. In the course of this work, we discovered an intense absorption band (up to ∼25%) centered at 0.44 μm in reflectance spectra of the low-Fe serpentine samples. As it turned out, the equivalent width of the band has a high correlation with content of Fe3+ (octahedral and tetrahedral) in the samples. It may be considered as a confirmation of the previously proposed mechanism of the absorption due to electronic transitions in exchange-coupled pairs (ECP) of Fe3+ neighboring cations. It means that the absorption feature can be used as an indicator of ferric iron in oxidized and hydrated low-Fe compounds on the surface of asteroids and other atmosphereless celestial bodies. Moreover, our measurements showed that the mechanism of light absorption is partially or completely blocked in the case of intermediate to high iron contents. Therefore, the method cannot probably be used for quantitative estimation of Fe3+ content on the bodies. Based on laboratory study of the analog samples, we conclude that spectral characteristics of Adeona, Interamnia, and Nina correspond to a mixture of CI–CM-chondrites and hydrated silicates, oxides and/or hydroxides. Spectral signs of sublimation activity on Adeona, Interamnia, and Nina at minimal heliocentric distances are likely discovered in the short-wavelength range (∼0.4–0.6 μm). It is suggested that such cometary-like activity at the highest surface temperatures is a frequent phenomenon for C and close type asteroids including considerable amounts of ices beneath the surface. A usual way of origin of a temporal coma of ice particles around a primitive asteroid is excavated fresh ice at recent impact event(s). The obtained reflectance spectra of two NEAs, (330825) 2008 XE3 and 2012 QG42, are predominantly featureless and could be attributed to S(C) and S(B)-type bodies, respectively. We discuss reasons why weak spectral features seen in reflectance spectra of the main-belt asteroids are not observed in those of NEAs.

Mechanisms of the disk formation in Be stars may differ from one star to another and cause variations in the circumstellar disk’s spectral characters. δ-Scorpii is one of the bright Be binary stars that has been classified as a Be star since the 1990s when the star showed a weak Balmer emission line. In this work we study the characteristics of the Be disk of this star in the optical region during close encounters with its companion in order to investigate the appearance of the Be phenomenon. This work presents a monitoring and analysis of δ-Scorpii’s spectral character in the optical region during the 2011 periastron passage. The line profiles and strength (EW), relative intensity (I/Ic) and V/R ratio of the circumstellar regions Hα, Hβ, Hγ and HeI 6678 are used in the investigation of the Be disk characters of δ-Scorpii. We found that all physical characteristics of the line profiles such as equivalent width (EW), full width at half maximum (FWHM), etc. were enhanced during the time of the periastron. We suggest that the effects are owed to the tidal interaction of the companion in close encounters which might have a strong influence on the appearance and survival of the Be phenomenon of δ-Scorpii.

X-ray photoelectron spectroscopy (XPS) is widely used in surface and materials laboratories around the world. It is a near surface technique, providing detailed chemical information about samples in the form of survey and narrow scans. To extract the maximum amount of information about materials it is often necessary to peak fit XPS narrow scans. And while indispensable to XPS data analysis, even experienced practitioners can struggle with their peak fitting. In our previous publication, we introduced the equivalent width (EWXPS) as both a possible machine automated method, one that requires less expert judgment for characterizing XPS narrow scans, and as an approach that may be well suited for the analysis of complex spectra. The EWXPS figure of merit was applied to four different data sets. However, as previously noted, other width functions are also regularly employed for analyzing functions. Here we evaluate two other width functions for XPS narrow scan analysis: the autocorrelation width (AWXPS) and the variance ( σ XPS 2 ). These widths were applied to the same four sets of spectra studied before: (a) four C 1s narrow scans of ozone-treated carbon nanotubes (CNTs) (EWXPS: ∼2.11–2.16 eV, AWXPS: ∼3.9–4.1 eV, σ XPS 2 : ∼5.0–5.2 eV, and a modified form of σ XPS 2 , denoted σ XPS 2 * : ∼6.3–6.8 eV), (b) silicon wafers with different oxide thicknesses (EWXPS: ∼1.5–2.9 eV, AWXPS: ∼2.28–4.9, and σ XPS 2 : ∼0.7–4.9 eV), (iii) hydrogen-terminated silicon surfaces, before and after modification with pentyl groups, and after annealing of the pentyl-terminated surface (EWXPS: ∼0.7–1.0 eV, AWXPS: ∼1.2–1.6 eV, and σ XPS 2 : ∼0.12–0.19 eV), and (iv) C 1s narrow scans from five different nanodiamond samples, three of which showed charging (EWXPS: ∼2.6–4.8 eV, AWXPS: ∼3.8–6.9 eV, and σ XPS 2 : ∼1.6–4.2 eV). All three of the width functions showed similar trends, except in the case of the C 1s spectra of the CNT samples, which were the most complex spectra evaluated, where σ XPS 2 showed poor correlation with the corresponding O/C ratios. Accordingly, we favor EWXPS and AWXPS. EWXPS is advantageous because it is conceptually simple, giving the most intuitive results. AWXPS has the advantage of not requiring the user to specify the height of the function at its maximum, which will be affected by noise. Because these functions are based on different mathematical operations/algorithms, best practices may involve the calculation of both widths for a set of narrow scans. The standard deviation, σXPS, i.e., the square root of the variance, was also examined. As expected, it gave results similar to σ XPS 2 .

X-ray Photoelectron Spectroscopy (XPS) is a widely used surface analytical tool that provides information about the near surface regions of materials. And while indispensable for XPS data analysis, peak fitting of narrow scans is often a fairly subjective exercise. Herein we introduce the equivalent width (EW) as an additional and less subjective figure of merit for XPS narrow scans. We believe that this parameter will prove particularly useful for analyzing series of similar or nominally identical spectra, perhaps as a component of an expert software system for the machine interpretation of spectra. It also appears to be useful, shedding light on the chemical state of materials, when additional information about a sample is known. The EW XPS is simply defined as the area of a narrow scan divided by the height of the maximum of its peak envelope. To limit any ambiguity in EW XPS for a series of spectra, we may also list the peak position of the maximum of the envelope (PE max ). The potential usefulness and limitations of the EW XPS and PE max parameters are demonstrated by their application to the narrow scans of: (i) four sets of ozone-treated carbon nanotubes (EW XPS ∼ 2.11–2.16 eV for a Shirley background, and up to 2.88 eV for no background, PE max ∼ 284.4–284.5 eV), (ii) a series of silicon wafers with different oxide thicknesses (EW XPS ∼ 1.5–2.8 eV, PE max ∼ 99–103 eV), (iii) hydrogen-terminated silicon before and after derivatization with pentyl groups, and after annealing of the pentyl-modified material (EW XPS ∼ 0.7–1.0 eV, PE max ∼ 25.9–26.1 eV), and (iv) five nanodiamond samples, where three of the spectra showed charging (EW XPS ∼ 2.6–4.9 eV, PE max ∼ 272.7–293.9 eV). In this final example, EW XPS was plotted against PE max to identify the region corresponding to the materials that showed the least charging. EW XPS and PE max appear to correlate with the expected chemistries of all the systems studied. We calculate EW XPS using a Shirley baseline and with no baseline at all. In setting the baseline limits for EW XPS , we consider the derivative of C 1s narrow scans. We also show the application of EW XPS to single, fitted components within a narrow scan.

We present the results of an investigation using near-infrared spectra of Pluto taken on 72 separate nights using SpeX/IRTF. These data were obtained between 2001 and 2013 at various sub-observer longitudes. The aim of this work was to confirm the presence of ethane ice and to determine any longitudinal trends on the surface of Pluto. We computed models of the continuum near the 2.405 μm band using Hapke theory and calculated an equivalent width of the ethane absorption feature for six evenly-spaced longitude bins and a grand average spectrum. The 2.405 μm band on Pluto was detected at the 7.5-σ level from the grand average spectrum. Additionally, the band was found to vary longitudinally with the highest absorption occurring in the N2-rich region and the lowest absorption occurring in the visibly dark region. The longitudinal variability of 12CO does not match that of the 2.405 μm band, suggesting a minimal contribution to the band by 13CO. We argue for ethane production in the atmosphere and present a theory of volatile transport to explain the observed longitudinal trend.

Exact expansions for Voigt line-shape total, line-tail and spectral bin equivalent widths and for Voigt finite spectral bin single-line transmittances have been derived in terms of optical depth dependent exponentially-scaled modified Bessel functions of integer order and optical depth independent Fourier integral coefficients. The series are convergent for the full range of Voigt line-shapes, from pure Doppler to pure Lorentzian. In the Lorentz limit, the expansion reduces to the Ladenburg and Reiche function for the total equivalent width. Analytic expressions are derived for the first 8 Fourier coefficients for pure Lorentzian lines, for pure Doppler lines and for Voigt lines with at most moderate Doppler dependence. A strong-line limit sum rule on the Fourier coefficients is enforced to define an additional Fourier coefficient and to optimize convergence of the truncated expansion. The moderate Doppler dependence scenario is applicable to and has been implemented in the MODTRAN5 atmospheric band model radiative transfer software. Finite-bin transmittances computed with the truncated expansions reduce transmittance residuals compared to the former Rodgers-Williams equivalent width based approach by ∼2 orders of magnitude.

The angular width and geometric line width in the spectral plane for the output incoherent imaging spectral line are discussed respectively on the basis of structure of prism monochromator, the relationship between the spectral width and line width of output incoherent imaging spectral line in the spectral plane is presented. The expression of monochromatic degree of output light in the exit slit plane is presented. The spectral resolving power of incoherent imaging spectral line and coherent imaging spectral line of the diffractive waves are discussed respectively, and the expressions of the spectral resolving power are presented respectively.

The spectral region in the vicinity of 5394 A contains three prominent photospheric spectral lines, which can be used as a solar plasma diagnostic tool. The occurrence of telluric lines in this region is a potential source of systematic and random errors in these solar spectral lines. The goal of our investigation was to determine the telluric line contamination of this interesting spectral region. Several series of high-resolution solar spectra within an interval of about 4 A around the 5394 A wavelength were observed at different zenith distances of the Sun. Comparison of these spectra has permitted identification of telluric lines in this spectral interval. The observations were carried out with the horizontal solar spectrograph of the Heliophysical Observatory in Debrecen. Telluric feature blending was identified in the blue and red wings of the Fe I 5393.2 A line, and in the local continuum of the Mn I 5394.7 A line. The blue wing of the Fe I 5395.2 A line is contaminated by a weak telluric feature too. The red continuum of this line has a more prominent telluric contamination. A dozen of water vapor telluric lines that determined the observed telluric features were identified in this spectral interval. The profiles of three telluric lines that have a significant influence on both the profiles of solar spectral lines and the level of local continuum were derived, and the variation of their parameters (equivalent width and central depth) with air mass were analyzed.

This study discusses the equivalent conductivity, the equivalent width, and the equivalent resistance of stress corrosion cracks from the viewpoint of eddy current testing. Four artificial stress corrosion cracks were prepared for this study, and their eddy current signals were gathered using two absolute pancake probes and two differential type plus point probes. Then their numerical models were evaluated using finite element simulations on the basis of the measured eddy current signals and their profiles revealed by destructive tests. The results of this study revealed that whereas the equivalent conductivity and the equivalent width depend on the exciting frequency utilized, the equivalent resistance of a crack has much less dependency, which agrees well with an earlier report. This study also revealed that the resistance of a crack depends on probe utilized. Larger probes tend to lead to smaller crack resistance. Pancake type probes tend to lead to larger crack resistance than plus point probes. Analyzing the results together with earlier reports indicates that cracks with a large equivalent conductivity tend to have large equivalent width, and supports the validity of assuming the minimum resistance of a stress corrosion crack whereas considering the conductivity and the width individually would not be viable.

We present equivalent width maps of the 1.98 and 2.13 μm SO2 ice absorption bands on the surface of Io. The data were taken on 17 April 2006 with the near-infrared mapping spectrometer, OSIRIS at the W.M. Keck Observatory, Hawaii. The maps show significant regional enhancements of SO2 ice over the Bosphoros, Media, Tarsus and Chalybes Regiones.

Frequencies in oscillating $\beta$ Cephei stars are usually inferred by means of radial velocities measured from the SiIII triplet 4552-4574 A. These lines, relatively insensitive to the variation of Teff through a pulsation cycle, show small equivalent width variations. In this study we aimed to verify if the behavior of radial velocities and equivalent widths measured from other ions are compatible with the one observed from SiIII lines and than to verify the possible vertical stratification along the stellar atmosphere. For this reason we selected from our spectra a number of, unblended and well isolated, CII, NII and OII lines besides the famous SiIII triplet. All those lines cover the range in optical depth between -2.1 and -0.5. Unfortunately, we did not find any differences in the radial velocities behavior line-by-line and then we derived the frequency of the principal radial mode combining all the velocities derived from each spectral line separately. The inferred frequency was f1=5.249677+/-0.000007 c/d. Another important task we would like to accomplish with this paper is to make available to the community our large sample of spectroscopic data, that is 932 velocities and equivalent widths measured from our sample of C, N, O and Si lines. All the spectra were acquired at the 1-meter class telescope of the stellar station of the INAF - Osservatorio Astrofisico di Catania, in the period starting from July, the 27th 2005 to November, the 1st 2006., Comment: 10 pages, 5 figures, to be published in New Astronomy

Background Gas, and in particular, cold gas is seen locally in many different locations (disks, halos, merger tails, and even in outflows). Which one is traced by QSO absorption lines, and in particular by the Mg II metal line? Given that QSO absorption lines probe galaxy halos out to 100 kpc and have no bias on the host galaxy luminosity, they are crucial to our understanding of galaxy evolution in general and feedback in particular. Strong Mg II absorbers with equivalent width W r 2796 > 1 A are in fact made of several (up to 20) sub-components or clouds. As a result, Wr is a measure of the line-of-sight velocity dispersion (Δv) of the clouds. Most models for QSO absorbers, except the outflow scenario, predict that the host-galaxy mass and the velocity dispersion Δv should correlate (by the Virial theorem). Goal If one could measure the mass for QSO absorbers, one could test whether mass and Δv are correlated. Result Using a statistical technique that does not require any spectroscopic follow-up, we find that the halo-mass Mh of the host-galaxy is anti-correlated with the equivalent width WΔv. This shows that the Mg II clouds are not virialized in the gaseous halos of the host-galaxies. If Mg II absorbers were virialized in galaxy halos, a positive mass-velocity correlation would have been observed. In addition, the kinematics of super-winds are most consistent with our Mh–Wr anti-correlation.

We have selected a large sample of star-forming galaxies (104,088) from SDSS-DR4 to derive oxygen abundance calibrations using equivalent width (EW) ratios of three metallicity-sensitive emission-line ratios: [N ii ]/Hα, ([O iii ]/Hβ)/([N ii ]/Hα), and [N ii ]/[S ii ]. The analytic calibrations of 12 + log(O/H) versus these line-ratios have been obtained as third-order polynomial fits, appropriate for metal-rich galaxies. These observed relations are consistent with photoionization models. These can be used as calibration references for future studies about metallicities of galaxies, especially when there are problems dealing with proper flux calibration for spectra, e.g., some of the current generation of wide-field galaxy surveys that use multi-object spectrographs.

We present high quality images of the uranian ring system, obtained in August 2002, October 2003, and July 2004 at 2.2 μm with the adaptive optics camera NIRC2 on the Keck II telescope. Using these data, we report the first detection in backscattered light of a ring (which we refer to as the ζ ring) interior to Uranus' known rings. This ring consists of a generally uniform sheet of dust between 37,850 and 41,350 km with an equivalent width EW = 250 ± 20 m (in 2004; or μ EW ≈ 50 m ), and extends inward to 32,600 km at a gradually decreasing brightness. This ring might be related to the Voyager ring R/1986 U 2, although both its location and extent differ. This could be attributed to a difference in observing wavelength and/or solar phase angle, or perhaps to temporal variations in the ring. Through careful modeling of the I / F of the individual rings at each ansa, we reveal the presence of narrow (few 100 km wide) sheets of dust between the δ and e rings, and between rings 4 and α . We derived a typical anisotropy factor g ≈ 0.7 in the scattering behavior of these particles. The spatial distribution and relative intensity of these dust sheets is different than that seen in Voyager images taken in forward scattered light, due either to a difference in observing wavelength, and/or solar phase angle or to changes over time. We may have detected the λ ring in one scan at μ EW ≈ 15 m , but other scans provided upper limits below this value. A single detection, however, would be consistent with azimuthal asymmetries known to exist in this ring. We further demonstrate the presence of azimuthal asymmetries in all rings. We confirm the eccentricity of ∼0.001 in rings 4, 5, 6, which in 2004 are ∼70 km closer to Uranus in the north (near periapse; lower I / F ) than in the south. We find a global optical depth of τ ∼ 0.3 in the main rings, and of τ = 0.25 ± 0.05 in the e ring.

A simple two-temperature model is developed to investigate the effect of stellar spots on the apparent magnitude and apparent lithium abundance of the star. For appropriate coverage factors, stellar spots can cause considerable variations in the apparent magnitude (about ±0.2 mag in V band and about −0.1 mag in B−V band) and equivalent width of LiI λ6708A (about −0.2−0.3 dex). In comparison with normal, spot-free stars, spotty stars exhibit bluer B−V colours, and narrower LiI λ6708A lines. Form the observed amplitude of luminosity variation, the change of spot coverage on the apparent disk Δ F s can be estimated to range from a few percent to 20%, hardly ever exceeding 30%.

Several experiments have measured solar EUV/UV flux in the last 10–15 years including SUSIM UARS, SOHO CELIAS SEM, and SOHO EIT and have generated multi-year spectral irradiance time series. Empirical models of these important sources of radiant energy are often based on solar activity proxies, most often, the solar 10.7 cm radio flux ( F 10.7 ). The short- and long-term correspondence of four solar activity index time series International Sunspot Number, the He 1083 Equivalent Width, F 10.7 , and the Mg II core-to-wing ratio are analyzed. All of these show well-correlated long-term behavior with F 10.7 and Mg II showing the greatest long-term agreement among all of the index pairs. However, during the recent maximum period of solar cycle 23, both the ISN and He 1083 have diverged significantly from the others. Recent UV and EUV measurements are compared with Mg II and F 10.7 to assess their value as solar activity proxies. In every case, Mg II was found to correlate more strongly than F 10.7 with the UV and EUV time series which correspond to a range of solar atmospheric temperatures of 4000K–2 MK. This correspondence indicates that the mechanisms underlying irradiances changes from upper photospheric chromospheric, transition region, and lower coronal solar atmospheric layers are closely linked.

This is the second paper in a series aiming at searching for infrared pumping lines for galactic 1612 MHz OH masers. Our paper I is devoted to the 34.6 mum absorption lines in ISO SWS spectra towards a large sample of galactic OH/IR sources. This paper analyzes the 53.3 mum line in the ISO LWS spectra towards a similar sample of OH/IR sources. A search with position radius of 1 arcmin in ISO Data Archive (IDA) results in 137 LWS spectra covering 53.3 mum associated with 47 galactic OH/IR sources and 4 ones associated with megamasers Arp 220 and NGC 253. (These two magamasers are included for comparison purpose only.) Ten of these galactic OH/IR sources are found to show and another 5 ones tentatively show the 53.3 mum absorption while another 7 sources (our group U1 and U2 sources) highly probably do not show this line. The source class is found to be correlated with the type of spectral profile: red supergiants (RSGs) and AGB stars tend to show strong blue-shifted filling emission in their 53.3 mum absorption line profiles while H II regions tend to show a weak red-shifted filling emission in the line profile. GC sources and megamasers mainly show symmetrical profile in the line core while megamasers tend to show an additional absorption tail on the blue side of the line profile. It is argued that the filling emission might be the manifestation of an unresolved half emission half absorption profile of the 53.3 mum, doublet which might be produced by the transitions among the two levels: (2)Pi(1/2)(J=3/2) and (2)Pi(1/2)(J=5/2) and their closely related levels. The 53.3 to 34.6 mum equivalent width (EW) ratio is close to unity for RSGs but much larger than unity for GC sources and megamasers while H II regions only show the 53.3 mum line. The pump rate defined as maser to IR photon flux ratio is approximately 5% for RSGs. The pump rates of GC sources are three order of magnitude smaller. Both the large 53.3 to 34.6 mum EW ratio and the small pump rate of the GC OH masers reflect that the two detected 'pumping lines' in these sources are actually of interstellar origin. The pump rate of Arp 220 is 32%-much larger than that of RSGs, which indicates that the contribution of other pumping mechanisms to this megamaser is important. A handful of non-detections of the 34.6 or 53.3 mum line or both can be explained partly by the genuinely weakness of the OH masers and partly by some other mechanisms weakening the IR pumping lines, such as clumpy OH shell or limb filling emission. (C) 2004 Elsevier B.V. All rights reserved.

We report on an observation of the Seyfert 1 galaxy ESO 141–G55 performed in October 2001 with the EPIC MOS cameras and Reflection Grating Spectrometers (RGS) on board the XMM – Newton observatory. We find the hard (3–10 keV) continuum slope, including reflection, to be somewhat flatter (Γ=1.72±0.06) than that of a typical broad-line Seyfert 1 galaxy. The spectrum shows a weak emission line at 6.45 ± 0.04 keV with a measured equivalent width of ≈ 40 eV. A broad spectral feature is observed around 7 keV that can be fitted by an absorption edge at 7.6 ± 0.1 keV. The extrapolation of the primary power law continuum to energies lower than 2 keV indicates the presence of a soft excess component contributing 45± 3% of the overall flux in the 0.3–2.0 keV energy range. This soft-excess cannot be explained solely by enhanced reflection from a highly ionized disk.

We report on an XMM – Newton observation of the Seyfert 1 galaxy NGC 3227 performed in November 2000. The observed X-ray spectrum above 4 keV is well fitted by a hard power law continuum (Γ≈1.5) and an absorption edge at 7.6 keV. An Fe K emission line with an equivalent width of 213 eV is detected at 6.4 keV. The line is narrow suggesting contribution from material in low ionization states (< Fe XVII) relatively far from a central black hole. The continuum is strongly absorbed at soft energies by a column of neutral gas (≈6.5×1022 cm−2) larger than previously measured and covering a significant fraction (≈ 90 %) of the central source. The soft X-ray continuum is also attenuated due to the presence of ionized material (ξ≈50–90 erg s−1 cm) suggesting the presence of a substantial amount of gas (NH≈2–91021 cm−2) in the vicinity (< 0.4 pc) of the nucleus. We find that NGC 3227 exhibits significant spectral variability above 2 keV on time scales of a few ksec during the XMM – Newton observations. This short term variability is likely related to variation in the continuum emission. Comparisons with previous observations indicate that variability on timescale of a month also involves a change in the column densities of neutral absorbing material along the line of sight to the nucleus.

A simple reliable theoretical approach is developed to calculate the equivalent width of copper and potassium resonance lines at 3247.54 and 7665 A using atomic absorption techniques. The calculations have been carried out for the two limiting cases of a pure Doppler (Gaussian) and Lorentzian (dispersion) line profiles. The more general case of a Voigt line profile leads to an efficient analytical formula permits a rapid estimate of the equivalent width with sufficient precision. The reliability of the approach has been verified by providing the curves of growth for the given spectral lines to describe the behavior of the equivalent width as the number of absorbing atoms in the ground state is increased. Allowance is made in the analysis for the dependence of the equivalent width for Voigt profile on the damping constant α, which is a measure of the half width of Lorentz profile relative to the Doppler profile.

We present spectral observations of Minor Planet 4 Vesta, of five V-type asteroids which are physically near Vesta, and of two V-type NEAs. We use these spectra to determine the presence or absence of a weak feature at 506.5 nm which is indicative of the presence of spin-forbidden Fe 2+ in sixfold coordination. As with our earlier observations [Cochran and Vilas, Icarus 134 (1998) 207–212], we find this feature at all observed rotational phases of Vesta and again see the trend that spectra at longitudes between 240° and 360° have a smaller 506.5 nm feature equivalent width than spectra obtained at other longitudes. Additionally, we searched for this feature in V-class main-belt and NEA asteroids and positively detected the feature in main-belt Asteroid 2579 Spartacus and possibly in 3376 Armandhammer. The other objects lacked the feature. Our results are compared with previous observations of this feature by Vilas et al. [Icarus 147 (2000) 119–128]. The spatial distribution of the bodies as a function of the presence of this feature was investigated. We discuss the implication of the presence of this feature and the depth of the 0.9 μm pyroxene band for the scenario that pieces of Vesta were transported, via the 3:1 and ν 6 resonances, to the NEAs, and thence to inclusion in our meteorite collections as HED meteorites.

Differences in the time development of solar activity indices are an important clue in the search for physical processes responsible for changing solar emission at various wavelengths. In this paper we describe our investigation of temporal relationships among two space-based indices, Lyman-α 121.6 nm emission (Lα) and the Mg II 280 nm core-to-wing ratio, and four ground-based indices – the 10.7 cm flux (F10), the He I 1083 nm equivalent width, the Ca II K 393.4 nm emission index, and the International Sunspot Number (ISN). We provide scatterplots of index pairs passed through a 2-year Gaussian filter during each available solar cycle, and we approximate the temporal relationships quantitatively as overall temporal offsets with uncertainties. We reconcile our findings with qualitative ideas concerning the variation of solar emissions with solar activity. Since the F10 and ISN time series are longer than four complete solar cycles, we are able to evaluate the reproducibility of temporal offsets over multiple solar cycles. The chief motivation for our work is to improve solar indicator analysis by providing a method of seeing and analyzing temporal relationships clearly and easily. We believe that future physical models of magnetic activity and spectral emissions in the solar chromosphere and transition region may make quantitative predictions of temporal relationships among full-disk solar indices for comparison with analyses such as ours.

Equivalent width is calculated for potassium and nickel resonance lines at 7665 and 2320 A. An efficient analytic Voigt profile expressions based on a simple combination of the pure Doppler and pure Lorentz limiting forms of the equivalent width have been used. A comparison is made between the results of this work and the numerical results which have been previously evaluated exactly by Jansson and Korb. The curves of growth, i.e., the equivalent width, W, versus τD are provided.

During the last three years we performed FTIR measurements of the polar atmosphere with the Sun or the Moon as a radiation source or in emission. The measurements have been made at the NDSC station (Network for the detection of stratospheric changes) in Ny-Alesund (79°N, 11°E) with commercially available, uncooled instruments. We retrieved the column densities of trace gases from the absorption spectra. The emission spectra have been analysed using the equivalent width method for the derivation of the column amounts of the trace gases. Aerosols are included in the simulation. We derived the column amounts of several trace gases including tropospheric (H2O) and stratospheric ones (HNO3, O3). The intercomparison between the results of emission measurements and independent ones (sonde-data and absorption spectra) revealed an average agreement for ozone of about 16%, whereas it is difficult to draw some conclusions for H2O due to larger atmospheric fluctuations. We compared the column amounts of nitric acid derived by the three methods. The Sun and emission data are in a good agreement, whereas the results derived from Moon absorption spectra slightly seem to overestimate the nitric acid and chlorine nitrate column amount.

In this paper, some CCD spectra of 6 cataclysmic variables: AB Boo, T CrB, UX UMa, AH Her, Z Cam, V426 Oph and 3 related objects: Leo3, UMa3 and EG UMa are presented. We also observed 5 late-type stars: 3 Dra, ν Vir, ψ Leo, 34 Boo, and 36 Com in order to provide comparison with the late-type component of the program systems. The observations were made using the 2.16 m telescope of Bejing Observatory with a Cassergrain spectrograph on 1997-04-15/17 at the Xinglong Station. The CCD spectra were obtained with a low resolution and a dispersion of 1.2A/pixel. The spectral region covered is from 5920A to 7072A, and from 7950A to 9180A for all the program stars and only 3390–8380A for AH Her. Representative spectra are given for each object. The equivalent width (EW) and FWHM of Hαand CaII triplet lines were determined. The radial velocities for 9 program stars were also determined. Implications of our results are discussed.

In this work, we present a new lineshape computing method. The lineshape, commonly known as the Voigt profile, is a convolution of the Gaussian and Lorentzian profiles. Moreover, we present a simple approach to describe the width of the Voigt profile as a function of the relative contributions of Gaussian and Lorentzian broadening. A novel expression of the equivalent width of Lorentz shapes can be calculated from numerical approximation. q 2000 Elsevier Science B.V. All rights reserved.

For rapidly rotating stars, the effect of gravity darkening on the equivalent width (EW) of spectral lines is very small, even when the rotation velocity is close to the critical velocity. But the effect on the full-width at half-maximum (FWHM) is relatively strong. At omega approximate to 0.99, the variation is 8%. For main-sequence stars in the range of spectral type B0 to B9, the variation of FWHM is almost independent of the spectral type when the rotation is small (omega < 0.8); for rapidly rotators (omega approximate to 0.99), the percentage variation of FWHM decreases with advancing spectral subclass.

In the framework of a quasi-spherical accretion model, we present preliminary results of detailed transfer calculations and Monte Carlo simulations showing the possible importance of multiple reflections and Compton scattering on/in a photoionized plasma, for the interpretation of the iron K line complex observed in several Seyfert galaxies. We computed both line and continuum emission resulting from the reprocessing of a primary continuum in a Thomson-thick shell of clouds subtending a large solid angle (ω/4π0.9) to a central point like source. When the clouds are significantly ionized (ξ ≳100, ξ = L/nR 2 ), an energy dependent amplification of the primary radiation occurs and must be taken into account. We find that one-ξ models cannot explain both the profile and equivalent width observed in MCG-6-30-15. However, a “two-phase mirror”, allowing for the presence of both low and high ionization clouds, seems compatible with available X-ray data. Assuming this is the main broadening mechanism, it is possible to constrain the state and distribution of the plasmas contributing to the observed profile.

The purpose of the study was to compare measured spectral width and maximum frequency with that predicted from ray models of geometric spectral broadening. Zero and finite beam-width models were used. Spectral data were acquired from a string phantom using two commonly-used linear array systems. Beam width and Doppler aperture sizes were measured using a needle hydrophone. The results showed that the experimentally measured data agreed best with the finite beam-width model. The zero beam-width model was in error by up to 50% for calculated spectral width, and up to 10% for maximum frequency. It is concluded that spectral width and maximum frequency are best calculated using the finite beam-width model, and that ultrasound manufacturers could improve the variation in spectral broadening measured at different locations on a single machine by adjusting the aperture size to give a constant subtended angle and beam width.

We report on a 50 ks observation of the bright Seyfert 1 galaxy MCG-6-30-15 with the Rossi X-ray Timing Explorer . The data clearly show the broad fluorescent iron line (equivalent width ∼ 242 eV for the scenario in which the primary X-ray source is above the accretion disk subtending an angle of 2π sr), and the Compton reflection continuum at higher energies. Upper limit constraints on the abundance versus reflective fraction relationship can already be placed at the 68 per cent confidence level.

We have obtained a hard X-ray spectrum of the ultraluminous infrared galaxy IRAS 20210+1121 (z = 0.056), whose optical spectrum is that of a Seyfert 2. The most significant feature is a strong Fe K line at 6.7 (6.5–7.0) keV in the rest-frame with equivalent width about 1 keV. This suggests that the observed X-ray continuum is scattered emission from a completely blocked AGN, a situation similar to that in NGC 1068. However, IRAS 20210+1121 has an observed 2–10 keV luminosity of 4 × 1042 erg s−1 (assuming H0 = 50km s−1 Mpc−1), about ten times higher than NGC 1068. If the scattering efficiencies of NGC 1068 and IRAS 20210 are similar, then this implies the presence of an extremely luminous X-ray source in IRAS 20210.

We present timing and spectral analyses of the ASCA observation of the Seyfert 1 galaxy NGC 985. The 0.6–10 keV spectrum of this source is complex: large residuals are evident below 1 keV when fitting the spectrum with a power-law model. Fitting a warm absorber model to the 0.6–2.5 keV spectrum gives α = 1.12 ± 0.04, Log N H WA = 21.97 ± 0.08 and LogU = 0.06 ± 0.09, but the residuals continue to show a deficit of counts between 0.9 and 1 keV. Adding an absorption line improves the fit, and the energy of thhe line is consistent with that of Kα NeIX-X resonant absorption lines. Hence, we confirm the presence of an ionized absorber along the line of sight to this source and interpret the further 1 keV spectral feature as the first detection of a strong resonant absorption line associated with this system. The extrapolation of this model above 2.5 keV produces large positive residuals above 3–4 keV. Fitting the data with a broken power law plus warm absorber model gives an acceptable ξ 2 and Δα ∼ 0.5. A narrow iron line at 6.4 keV (quasar frame) of equivalent width 138 −110 +64 eV is also present in the ASCA data.

Preliminary results obtained from BeppoSAX observation of the starburst galaxy NGC253 are presented. X-ray emission from the object is clearly extended but most of the emission is concentrated on the optical nucleus. Preliminary analysis of the LECS and MECS data obtained using the central 4' region indicates that the continuum is well fitted by two thermal components at 0.9 keV and 7 keV. Fe K line at 6.7 keV is detected for the first time in this galaxy; the line has an equivalent width of ~300eV. The line energy and the shape of the 2-10 keV continuum strongly support thermal origin of the hard X-ray emission of NGC253. From the measurement of the Fe K line the abundances can be unambiguously constrained to ~0.25 the solar value. Other lines clearly detected are Si, S and Fe XVIII/Ne, in agreement with ASCA results., 4 pages, LateX, 2 figures (included). Uses espcrc2.sty (included) To appear in The Active X-ray Sky: Results from BeppoSAX and Rossi-XTE, Rome, Italy, 21-24 October, 1997. Eds.: L. Scarsi, H. Bradt, P. Giommi and F. Fiore

Our spectroscopic observation of the Be/X-ray binary LSI+65°010 showed a dramatic variation in November 1992 with an increase by a factor of more than 3 in the equivalent width of the H α emission line. This supports the view that the primary is a Be star rather than a supergiant. A well-defined double-peaked profile in seen in the spectrum of September 1994: while the red peak remained at 6563 A, the blue one was −7.2A to the blue. We suggest that such a profile is caused by the superposition of two emission lines, one from the shell of the Be star, one from an H II region around the neutron star. This provides, for the first time, direct observational evidence for the existence of a H II region around compact object and caused by X-ray emission. On 1992-11-04, the red side of the H α line did not change while the blue side was greatly enhanced. We suggest that this may be caused by the H II region around the neutron star.

Spectroscopic observations of Jupiter and Saturn are here reported to show the possible applications to the future data acquired by the instrument VIMS ( Visible and Infrared Mapping Spectrometer ) on board of the Cassini Mission. The following images and spectra have been acquired by a similar instrument called VNIR ( Visible and Near Infrared Spectrometer ) during several observational campaigns. We put our attention on the distribution of the methane in the visible and infrared wavelengths since it is the main absorber in the atmosphere of Jupiter and Saturn in this wavelength range We have studied the ratio between the CH 4 equivalent width and the integral of the absorption coefficient of methane at different wavelengths. This kind of study permits to obtain many indications about the vertical distribution of methane and about the vertical structure of the planetary atmosphere. Classical questions when studying planetary atmospheres are the vertical temperature-pressure profiles, composition, structure and dynamics. Usually these questions are addressed with a medium to high resolution spectrometer. Imaging spectroscopy permits to put together at the same time both spatial and spectral information and its use allows us to resolve some of the above-mentioned questions such as identification of main atmospheric components, vertical analysis of the atmosphere, spectral analysis of clouds and vortices and determination of global wind pattern.

Moderate spectral resolution observations of the 505-nm Fe 2+ pyroxene feature in the reflectance spectrum of Vesta were acquired across the complete surface of the asteroid. The feature is consistently centered at 506.54 nm, suggesting an augite (high-calcium) composition. Variations in the equivalent width of the feature correlate with topographically high terrain on Vesta's surface, and could be due to the presence of another material (possibly olivine), or particle size variations, or both.

We present a series of optical spectroscopic and infrared photometric observations of the Be/X-ray system X Per in 1992-95. Some phenomena in this new emission phase turn out to be unique in comparison with former observations. First, although the V magnitude only recovered its original maximum brightness from 1974 to 1991, the equivalent width (EW) of H-alpha emission line and JHK magnitudes exceeded the values recorded before, and this means that the circumstellar envelope of X Per in the new emission phase is more extensive and denser. Second, we have for the first time observed in X Per that the EW of H-alpha line increased rapidly while the JHK magnitudes declined considerably. Our optical spectroscopic data support the rotating ring model of the envelope and confirm the existence of the double-ring structure, with which the observed unusual phenomena may be fairly well interpreted.

Infrared absolute line intensities of the ν 3 band of 12 CH 3 F have been measured around 9.5 μm using a diode-laser spectrometer. These line strengths were obtained from the equivalent width method and, for a few lines, by fitting a Rautian profile to the measured shape of the lines. From these results, we have deduced the vibrational bandstrength ( S v 0 = 379.2 ± 5.9 cm −2 ·atm −1 at 296 K) and the first Herman–Wallis factor (α = 0.35 × 10 −3 ± 0.10 × 10 −3 ).

The 11 July 1992 occultation of Uranus by U103 (mK= 10.1) was observed using the 5-m Hale telescope on Palomar Mountain in California, the 4-m telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile, and the nearby 2.2-m telescope at European Southern Observatory (ESO). All observations were taken using InSb aperture photometers andK(λ ∼ 2.2 μm) filters and provided high-quality profiles of the uranian rings. The ESO and Palomar ring event times have been incorporated into a comprehensive orbit model for the elliptical rings using all available Earth-based and Voyager occultation data. The kinematical model was used to determine the radius scale and geometry of the U103 occultation, as well as to provide absolute timing calibration for the CTIO light curve, which was reconstructed from two-dimensional digital scans of a high-speed strip chart. All nine classical rings were clearly observed during both ingress and egress. In addition, a sharp feature appeared in the CTIO ingress light curve with an orbital radius of 50,026.89 ± 0.39 km, very close to the mean radius of the λ ring of 50,026.3 ± 0.6 km found by M. R. Showalter (Science267, 490–493, 1995) from an analysis of Voyager 2 images. The CTIO feature is well above the noise: its equivalent width ofE= 0.32 ± 0.14 km corresponds to a 5–σ detection. It is the only such signature in the entire CTIO lightcurve, other than the previously known rings. The characteristic ring-like shape of the profile, its high SNR, and its radial location all support the identification of this feature as an Earth-based detection of the λ ring. At the same time, if the ring were azimuthally homogeneous withE≳ 0.32 km, it would have been clearly visible in the CTIO egress and Palomar light curves, but no such features were found. The λ ring is thus azimuthally clumpy, resembling to some degree Neptune's arc-like Adams ring. At the nearby ESO station, a suggestive ingress feature appeared with a radius of 50,023.01 ± 0.28 km, but the data are too noisy to permit a positive identification. The orbital characteristics of the λ ring and its azimuthal brightness profile cannot be uniquely extrapolated from the Voyager encounter epoch to the time of the U103 occultation because the mean motion and orbital radius of the ring are too uncertain. However, additional detections in archival Earth-based occultation data or from future observations could allow a much better determination of the dynamics of this dusty and clumpy ring.

Explicit expressions are derived for the photon single-flight escape probability associated with the Voigt spectral line profile, in media specified by a given temperature, and for scattering described by complete frequency redistribution. The expressions, based on equivalent width representations given by previous authors, are evaluated and compared with evaluations obtained by direct integration of the defining expression. A partial tabulation and plots of the escape probability are provided.

Data from eight stellar occultations by Neptune between 1984 and 1988 are analyzed to set limits on the optical depths of the continuous Adams and Le Verrier Rings, and to search for previously unidentified occultations by the arcs in the Adams Ring. We employ the approach introduced by Sicardy et al . (1991), Icarus 89, 220-243) and convert the raw lightcurves to radial profiles of equivalent width E ( r ), the fraction of incident starlight removed by ring material at normal incidence integrated over a specified radial range, or "window." In order to optimize the search for narrow rings, the window length is fixed at 15 km. Radii in Neptune's equatorial plane are calculated using the Neptune pole direction determined by Jacobson et al . (1990), AIAA/AAS Astrodynamics Conference , pp. 157-167). Using data from the occultation of 20 August 1985, we set a 3 σ upper limit of 75 m on the equivalent width of the Adams Ring at a longitude 120° away from tile arc region, near the location of minimum ring brightness in the Voyager images (Showalter and Cuzzi 1994, in preparation). This limit is for a maximum ring width of 15 km; for a maximum ring width of 50 km, the corresponding upper limit is E ≤ 210 m. Combining the results from this data set with similar upper limits obtained by Sicardy et al . (1991) with a 50-km window size, and assuming that the Adams Ring is azimuthally homogeneous away from the arc region, we find that the equivalent width of this ring is ≤90 m at the 90% confidence level, or ≤ 5% of the measured equivalent width of the Egalite arc. A comparison of this result with the relative brightnesses of ring and arcs observed at low phase angles in Voyager images (Showalter and Cuzzi 1994) suggests either that the particles in the Adams Ring have higher albedos than those confined within the arcs, or that the width of the continuous ring significantly exceeds 50 km. The 20 August 1985 lightcurve has also yielded the first tentative earth-based detection of the Le Verrier Ring, with an overall radial width of 135 km and an equivalent width of 520 ± 55 m at λ2.2 μm which are similar to results obtained by the Voyager Photopolarimeter occultation experiment at λ0.27 μm (Horn et al . 1991, Geophys. Res. Lett. 17, 1745-1748). The ratio E PPS / E 2.2 μm = 1.3 ± 0.3. The mean radii of both occultation profiles—53055 and 53125 km, respectively, projected into the ring plane determined by Porco et al . ( Neptune and Triton Conference, Tucson, AZ, 1992 ) and Showalter and Cuzzi (1992), Bull. Am. Astron. Soc. 24, 1029)—are significantly less than the image-derived radius of 53200 ± 20 km (Porco et al . 1992). It is conceivable that this discrepancy could be due to an unrecognized inclination and/or eccentricity. A comparison of our putative detection of the Le Verrier Ring with upper limits set by Sicady et al . (1991) suggests that this ring must be azimuthally inhomogeneous on scales of ∼10°, if our detection is real. A feature in the vicinity of the Adams Ring at the predicted longitude of the Liberte arc was seen in data obtained on 9 July 1988, but a discrepancy of 270 km between the calculated radius and the known semi-major axis of the ring seems to rule out an identification with the arc. Attempts to fit a precessing ellipse model to all available occultation data for the Adams Ring which will also accommodate this observation are in vain. The remaining occultation-derived radii for this ring are found to be consistent with the resonant-perturbation model of Porco (1991, Science 253, 995-1001), and suggest strongly that the Adams Ring lies in, or very close to, Neptune's equatorial plane.

The far and extreme ultraviolet (FUV/EUV) solar flux determines the photodestruction rates of H 2 O and OH in cometary comae and affects their spatial density distributions. Between the minimum and maximum of the solar activity cycle, the solar flux varies by as much as a factor of 2-3 at some FUV and EUV wavelengths. From recent cross section measurements, a solar spectrum model using the He 1 λ10830 equivalent width and 10.7 cm flux as solar activity indices, and estimates of destruction rates due to the solar wind, we can estimate the H 2 O and OH lifetimes appropriate to any observation since 1975. The calculated H 2 O and OH lifetimes against direct photodissociation both vary by 30%, though the additional destruction of OH through predissociation accounts for most of the 70% variability in its total lifetime. Lifetimes for H 2 O and OH corresponding to the solar activity minimum and maximum are presented along with parametrizations to estimate lifetimes appropriate for any observation date. As a by-product, we calculate the time-variable yields for producing OH( A 2 Σ + ), O( 1 D ), and O( 3 P ) from H 2 O and OH. The H 2 O and OH lifetimes were included in a vectorial density distribution model and tested against International Ultraviolet Explorer (IUE) spacecraft observations in which the OH coma was spatially mapped, and the agreement is quite good. The implications of this new OH modeling on the interpretation of observations are exemplified in a brief analysis of Q H 2 O for comets Bradfield (1979 X) and Austin (1990 V).

A set of relatively simple analytical expressions is given for the rapid computation of the curve growth of a spectral line over the whole range of damping-constant or mixing-parameter values. The computed equivalent width of a pure Gaussian (Doppler broadened) or pure Lorentz (naturally plus collisionally broadened) line-shape is accurate within 1% while, for the mixed Voigt lineshape, it is generally accurate within 1%, with a maximum of about 5% in some narrow regions of the curve of growth.

Results obtained from an analysis of the ionospheric electron content (IEC) data collected at several stations in the Northern Hemisphere during December 1980–December 1985, when the 10.7 cm solar flux index ( F 10.7 ) varied from 66 to 303, are presented. Diurnal maximum IEC value (IEC max ) increases linearly with ( F 10.7 ), as expected, for values of ( F 10.7 ) less than about 200; at higher values of ( F 10.7 ), contrary to expectation, IEC max saturates at all stations. The observed variation of IEC max is interpreted as convincing ionospheric evidence for a nonlinear relationship between solar e.u.v. and 10.7 cm fluxes during intense solar cycles. Variation of the e.u.v. flux obtained from the latest version of the SERF2 solar e.u.v. flux model for the intense solar cycle 21 agrees with this interpretation. Lyman-α (1216 A) and He I (10,830 A) equivalent width data, measured during the same period as the IEC observations and used as independent data sets in the solar e.u.v. flux model, also show nonlinear variations with ( F 10.7 ).

The high resolution (0.049–0.145A) and high signal-to-noise ratio (100–600) Reticon and CCD spectra of 57 binaries of the RS CVn type were obtained with the coude spectrograph of the McDonald Observatory 2.1m telescope and the Yunnan Observatory 1m telescope for an analysis of the correlation between Li abundance and chromospheric activity. The Li abundance of 57 RS CVn systems, which include 76 detected components, has been determined through the observed equivalent widths of the Li doublet (6707.761A + 6707.912A) and Kurucz's model atmospheres. By the method of the comprehensive analysis of the atmospheric model the abundances of [Fe/H], [Ti/Fe] and logN(Li) have been calculated for 10 of the above mentioned binaries. We have made statistical analysis of the correlations between the lithium abundance and the effective temperature Teff as well as the projected rotational velocity, v sin i. The results show that the Li abundance tends to decrease with the drop of Teff. On the other hand, the Li abundance has a tendency to decrease with the increase of v sin i, but the dispersion of this correlation is very large. In particular, in the range of v sin i

The forbidden oxygen line at 6300 A has been observed with UVES on the ESO VLT for 13 dwarf and subgiant stars ranging in metallicity from [Fe/H]≃−0.7 to −1.8. The spectra obtained have a resolution of R =55 000 and S / N ≃400. After removal of telluric lines, the equivalent width of the [O i ] line could be measured with an accuracy of 0.2 to 0.3 mA. Using these data and the equivalent widths of eight weak Fe ii lines, the trend of [O/Fe] with [Fe/H] has been derived. Below [Fe/H]≃−1.0 the oxygen-to-iron ratio is nearly constant at a level of [O/Fe]≃0.4 in contradiction to recent results from UV OH lines.