Non-LTE analysis of the formation of KI lines in the spectra of A-K stars

The non-LTE formation of KI lines in the spectra of A-K stars is analyzed. The computations are based on a 36-level model of the neutral potassium atom for blanketed LTE Kurucz model atmospheres with T _eff=4000–10000 K, logg=0.0–4.5, and [M/H]=(0.0)–(?2.0). The KI atoms in the atmospheres of these stars are in states of moderate and strong “over-recombination.” A number of atomic parameters are refined using the profiles and equivalent widths of five lines in the solar spectrum. The classical van der Waals damping constants must be increased by factors of 2–60 to fit the observed profiles. The non-LTE solar potassium abundance—logε (K)=5.14—corresponds to the meteoritic abundance. Non-LTE corrections to the potassium abundance are important and equal to ?0.4...?0.7 dex for the λ7699 Å line and ?0.15...?0.3 dex for the λλ12522, 12432, and 11769 Å lines.     

Non-LTE effects in Mg I lines for various types of stars

We have performed a detailed statistical-equilibrium analysis based on a 49-level model of the magnesium atom for the atmospheres of stars of various spectral types: T _eff=4500–12000 K, logg=0.0–4.5, and [M/H]=0 to ?3. In the atmospheres of stars with T _eff>5500 K, deviations from LTE for Mg I are due to photoionization by ultraviolet radiation from the 3p level; i.e., neutral magnesium is in a state of “superionization.” When T _eff<5500 K, the populations of the Mg I levels differ from their LTE values due to radiative processes in bound-bound transitions. We analyzed Mg I lines in the solar spectrum in order to empirically refine certain atomic parameters (the van der Waals broadening constant C ₆ and cross sections for photoionization and collisional interactions with hydrogen atoms) and the magnesium abundance in the solar atmosphere. We studied non-LTE effects for five Mg I lines for a wide range of stellar parameters. In the case of dwarfs and subdwarfs, the magnitude of non-LTE corrections to magnesium abundances does not exceed 0.1 dex for the λλ 4571, 4703, 5528, and 5711 Å lines but can be as large as ±0.2 dex for the λλ 3829–3838, 5172, and 5183 Å lines. The non-LTE corrections for giants and supergiants do not exceed 0.15 dex for the λλ 4571 and 5711 Å lines but can reach ±0.20 dex and even more for the λλ 4703, 5528, 3829–3838, 5172, and 5183 Å lines.     

Evolutionary status of the spectral variable BD + 48°1220 = IRAS 05040+4820

Based on high-resolution observations (R = 60 000 and 75 000), we have studied the optical spectral variability of the star BD + 48°1220, identified with the IR source IRAS 05040+4820. We have measured the equivalent widths of numerous absorption lines of neutral atoms and ions at wavelengths from 4500 Å to 6760 Å, as well as the corresponding radial velocities. We use model atmospheres to determine the effective temperature T _eff = 7900 K, surface gravity log g = 0.0, microturbulence velocity ξ _t = 6.0, and the abundances for 16 elements. The star’s metallicity differs little from the solar value: [Fe/H] = ?0.10 dex. The main peculiarity of the chemical composition of the star is a large helium excess, derived from the Hel λ 5876 Å absorption, [He/H] = +1.04, and the equally large oxygen excess, [O/Fe] = +0.72 dex. The carbon excess is small, [C/Fe] = +0.09 dex, and the ratio [C/O] < 1. We obtained an altered relation for the light-metal abundances: [Na/Fe] = +0.87 dex with [Mg/Fe] = ?0.31 dex. The barium abundance is low, [Ba/Fe] = ?0.84 dex. It is concluded that the selective separation of elements onto dust grains of the envelope is probably efficient. The radial velocity of the star measured from photospheric absorption lines over three years of observations varies in the interval V _⊙ = ?(7–15) km/s. Time-variable differential line shifts have been revealed. The entire set of available data (the luminosity M _v ≈ ?5 ^m , velocity V _lsr ≈ ?20 km/s, metallicity [Fe/H] = ?0.10, and peculiarities of the optical spectrum and chemical composition) confirms the status of BD + 48°1220 as a post-AGB star with He and O excesses belonging to the Galactic disk.     

Resonance potassium and sodium lines in the spectra of ultracool dwarfs

We discuss the methodological problems and results of computations of the spectral energy distributions (SEDs) of L dwarfs. Over a wide wavelength interval (λλ4000–10 000 Å), the spectra of these stars are determined to a considerable extent by absorption in resonance lines of potassium (7666.961, 7701.031 Å) and sodium (5891.518, 5897.489 Å). We compute the extended wings of these lines using the theory of quasi-stationary broadening. We compute the cores and nearby wings (up to Δλ = 40 Å from the line center) of the KI and NaI lines in a collisional approximation (van der Waals theory). In our modeling of the SED of the ultracool dwarf 2MASS J15232263+3014562 (L8), we find that the observations agree best with the COND atmospheric models of Allard et al. with T _eff = 2200 K and log g = 6.0.     

The mass of the black hole in the X-ray binary LMC X-1

A dynamical estimate of the mass of the black hole in the LMC X-1 binary system is obtained in the framework of a Roche model for the optical star, based on fitting of the He I 4471 Å and He II 4200 Å absorption lines assuming LTE. The mass of the black hole derived from the radial-velocity curve for the He II 4200 Å line is m_x = 10.55 M_⊙, close to the value found earlier based on a model with two point bodies [1].     

Neutron-capture elements in halo,thick-disk,and thin-disk stars: Neodymium

We have derived the LTE neodymium abundances in 60 cool stars with metallicities [Fe/H] from 0.25 to ?1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of λ/Δλ?60 000 and signal-to-noise ratios of 100–200. We have improved the atomic parameters of NdII and blending lines by analyzing the corresponding line pro files in the solar spectrum. Neodymium is overabundant with respect to iron in halo stars, [Nd/Fe]=0.33±0.09, with the [Nd/Fe] ratio decreasing systematically with metallicity when [Fe/H]>?1. This reflects an onset of efficient iron production in type I supernovae during the formation of the thick disk. The [Nd/Ba] and [Nd/Eu] abundance ratios behave differently in halo, thick-disk, and thin-disk stars. The observed abundance ratios in halo stars, [Nd/Ba]=0.34±0.08 and [Nd/Eu]=?0.27±0.05, agree within the errors with the ratios of the elemental yields for the r-process. These results support the conclusion of other authors based on analyses of other elements that the r-process played the dominant role in the synthesis of heavy elements during the formation of the halo. The [Nd/Ba] and [Nd/Eu] ratios for thick-disk stars are almost independent of metallicity ([Nd/Ba]=0.28(±0.03)?0.01(±0.04) [Fe/H] and [Nd/Eu]=?0.13(±0.03)+0.05(±0.04) [Fe/H]) but are smaller in absolute value than the corresponding ratios for halo stars, suggesting that the synthesis of s-process nuclei started during the formation of the thick disk. The s-process is estimated to have contributed ?30% of the neodymium produced during this stage of the evolution of the Galaxy. The [Nd/Ba] ratio decreases abruptly by 0.17 dex in the transition from the thick to the thin disk. The systematic decrease of [Nd/Ba] and increase of [Nd/Eu] with increasing metallicity of thin-disk stars point toward a dominant role of the s-process in the synthesis of heavy elements during this epoch.     

Abundances of carbon,nitrogen, oxygen,and other elements in the atmosphere of the giant 30 LMi

We have studied the star 30 LMi using high-dispersion CCD spectra and photographic observations. We estimate the star's effective temperature T_eff=7210 K, gravity log g=3.34, and microturbulence velocity ξ_t=5.8 km/s. The carbon abundance, log ?(C)=8.57, is close to the solar value. Nitrogen (log ?(N)=7.81), oxygen (log ?(O)=8.76), and sulfur (log ?(S)=7.20) are slightly underabundant compared to the Sun, by ?0.16 dex, ?0.11 dex, and ?0.13 dex, respectively. A relatively large underabundance of ?0.27 dex was found for titanium (log ?(Ti)=4.75), whereas zinc shows an over-abundance by +0.21 dex (log ?(Zn)=4.81). Sodium (log ?(Na)=6.26), silicon (log ?(Si)=7.57), calcium (log ?(Ca)=6.38), chromium (log ?(Cr)=5.62), iron (log ?(Fe)=7.51), nickel (log ?(Ni)=6.34), and yttrium (log ?(Y)=2.34) exhibited abundances close to the solar values. We find no chemical anomalies characteristic of Am stars or δ Scuti stars in the spectrum of 30 LMi.     

Abundances of carbon,nitrogen, oxygen,and other elements in the atmospheres of the giants 25 Mon and HR 7389

An analysis of high-resolution CCD spectra of the giant 25 Mon, which shows signs of metallicity, and the normal giant HR 7389 is presented. The derived effective temperatures, gravitational accelerations, and microturbulence velocities are T_eff = 6700 K, log g = 3.24, and ξ _t = 3.1 km/s for 25 Mon and T_eff = 6630 K, log g = 3.71, and ξ _t = 2.6 km/s for HR 7389. The abundances (log ε) of nine elements are determined: carbon, nitrogen, oxygen, sodium, silicon, calcium, iron, nickel, and barium. The derived excess carbon abundances are 0.23 dex for 25 Mon and 0.16 dex for HR 7389. 25 Mon displays a modest (0.08 dex) oxygen excess, with the oxygen excess for HR 7389 being somewhat higher (0.15 dex). The nitrogen abundance is probably no lower than the solar value for both stars. The abundances of iron, sodium, calcium (for HR 7389), barium, and nickel exceed the solar values by 0.22–0.40 dex for both stars. The highest excess (0.62 dex) is exhibited by the calcium abundance for 25 Mon. Silicon displays a nearly solar abundance in both stars—small deficits of ?0.03 dex and ?0.07 dex for 25 Mon and HR 7389, respectively. No fundamental differences in the elemental abundances were found in the atmospheres of 25 Mon and HR 7389. Based on their T_eff and log g values, as well as theoretical calculations, A. Claret estimated the masses, radii, luminosities, and ages of 25 Mon (M/M_⊙ = 2.45, log(R/R_⊙) = 0.79, log(L/L_⊙) = 1.85, t = 5.3 × 10⁸ yr) and HR 7389 (M/M_⊙ = 2.36, log(R/R_⊙) = 0.50, log(L/L_⊙) = 1.24, t = 4.6 × 10⁸ yr), and also of the stars 20 Peg (M/M_⊙ = 2.36, log(R/R_⊙) = 0.73, log(L/L_⊙) = 1.79, t = 4.9 × 10⁸ yr) and 30 LMi (M/M_⊙ = 2.47, log(R/R_⊙) = 0.73, log(L/L_⊙) = 1.88, t = 4.8 × 10⁸ yr) studied by the author earlier.     

Non-LTE analysis of the formation of EuII lines in the atmospheres of solar-type stars

A method to analyze the statistical equilibrium of the EuII ion based on a 36-level model atom has been developed. The formation of EuII lines without assuming local thermodynamic equilibrium (LTE) is considered for T _eff=5500–7000 K, logg=4.0, and metallicities [A] from 0 to ?1.5. Non-LTE effects in the level populations are primarily due to radiative pumping of excited states from the ground and low-lying levels, which leads to over-population of upper relative to lower levels. As a result, the studied λ4129 and λ6645 Å lines are weaker than in the LTE case. However, due to the small energy differences between even low-lying EuII levels, collisional coupling is strong, and deviations from LTE in EuII lines are modest: for the Sun, non-LTE corrections to the abundance are only 0.04 dex. The non-LTE effects grow with an increase in the effective temperature and with a decrease in the metallicity, so that non-LTE abundance corrections can reach 0.12 dex for T _eff=5500K, logg=4.0, [A]=?1.5 and 0.1 dex for T _eff=7000K, logg=4.0, [A]=0. The effect of inaccuracy in the atomic parameters for EuII on the non-LTE calculations is examined. Analysis of the profiles of the solar EuII λ4129 and λ6645 Å lines is used to empirically refine estimates of the efficiency of collisional processes in forbidden transitions in establishing the distribution of EuII ions over excited states.     

Abundances of carbon,nitrogen, oxygen,and other elements in the atmospheres of the giants 15 ori and 22 <Emphasis Type="Italic">ɛ</Emphasis> sex

We have used high-resolution spectra to study the giants 15 Ori and 22 ? Sex. The effective temperature T _eff = 7060 K, gravity log g = 3.16, and microturbulence velocity ξ _t = 3.5 km/s were determined for 15 Ori, with T _eff = 7350 K and log g = 3.90 for 22 ? Sex (the microturbulence velocity for 22 ? Sex was assumed to be ξ _t = 2.7 km/s). We estimated the abundances of C, N, O, Na, Si, Ca, Fe, and Ba (N and Ba, for 15 Ori only). The abundances of carbon, iron, and oxygen in 22 ? Sex are higher than the solar values by +0.31 dex, +0.33 dex, and +0.18 dex, respectively, while the calcium abundance is ?0.19 dex below the solar level. For 15 Ori, we find a slight carbon excess (+0.19 dex), a slight nitrogen deficiency (?0.13 dex), and a considerable deficiency of silicon (?0.42 dex). The abundances of the remaining elements in both stars are near-solar. We find no substantial differences between the abundances derived for 15 Ori and 22 ? Sex and the results of earlier studies of giants by both ourselves and Erspamer and North. A comparison of the atmospheric elemental abundances of giants and δ Scuti stars indicates that the abundances of some lighter elements (oxygen, sodium, silicon, and possibly nitrogen) are somewhat lower for δ Scuti stars than for A-F giants. We determined the masses, radii, luminosities, and ages for 15 Ori and 22 ? Sex.     

CaII line formation in the spectra of irradiated atmospheres

We have studied the effect of external radiation on the formation of LTE and non-LTECaII lines in the spectra of A-M-star atmospheres. Three frequency distributions were chosen for the external radiation: X-ray radiation specified by the power law \(I_v^ + = I_{0^v } ^{ - 0.6} \) at 1–16.5 keV and UV radiation specified by blackbody distributions with the temperatures T_rad=50000 and 15000 K. We analyze the influence of variations in the irradiating flux and its angle of incidence on the profiles and equivalent widths of the λλ3933, 3968 Å resonance doublet and the λλ8498, 8542, 8662 Å infrared triplet. For any type of external radiation, allowing for deviations from LTE decreases the reflection effects for the CaII lines. We conclude that the CaII profiles do not display emission components in the spectra of optically thick stellar atmospheres irradiated by X-rays. Therefore, CaII emission lines observed in the radiation of cataclysmic variables must be formed in an optically thin plasma. CaII emission lines are likely to form in the spectra of stars with UV irradiation if CaII is the dominant ionization state in atmospheric layers close to the depths at which the continuum is formed. As a result, the spectra of symbiotic variables with hot primaries can contain CaII lines originating on the surfaces of the M-giants and supergiant secondaries due to reflection effects. These lines can be used to analyze the reflection effects and the temperature structure in the atmospheres of the secondaries only if non-LTE effects are included. In the spectra of close binaries with cool white dwarfs, CaII emission lines originate in the irradiated atmospheres of the secondaries under conditions close to thermalization. These lines can be used to study the reflection effects and calcium abundances even in an LTE approximation. We calculated the profiles and equivalent widths of CaII lines in the spectra of the four precataclysmic variables BE UMa, EG UMa, MS Peg, and HR Cam. The observed and theoretical reflection effects in the λλ3933, 8542 Å emission lines for the specified parameters of the systems and a solar calcium abundance in the atmospheres of the red dwarfs are in good agreement.     

The impact of reflection effects on the parameters of the old pre-cataclysmic variables MS Peg and LM Com

We have determined the main parameters of the old precataclysmic variable stars MS Peg and LM Com. The radial velocities of the components, reflection effects in the spectra, and light curves of the systems are studied based on model stellar atmospheres subject to external irradiation. Forty-seven moderate-resolution spectra for MS Peg and 57 for LM Com obtained with the 6-m telescope of the Special Astrophysical Observatory are used to derive the refined orbital periods of 0.1736660 days and 0.2586873 days, respectively; the orbital eccentricities do not exceed e=0.04. The mass (M _w =0.49e_⊙) and radius (e _w =0.015R_⊙) of the MS Peg primary calculated using the gravitational redshift correspond to those for a cooling carbon white dwarf with a thin hydrogen envelope. The parameters of the red dwarf (M _r =0.19M_⊙, T_eff=3560 K, R _r =0.18R_⊙) are close to those derived from evolutionary tracks for main-sequence M stars with solar chemical composition. The radius (R _r =0.22R_⊙) and temperature (T_eff=3650 K) of the LM Com secondary exceed theoretical estimates for main-sequence stars with masses of M _r =0.17M_⊙. The luminosity excess of the red dwarf in LM Com can be explained by a prolonged (T>5×10⁶ yrs) relaxation of the M star to its normal state after the binary leaves the common-envelope stage. For both systems, theoretical U, B, V, and R light curves and spectra calculated using the adopted sets of parameters are generally consistent with the observations. This confirms the radiative origin of the hot spots, the unimportance of horizontal radiative transport, and the absence of large-scale velocity fields with high values (V_trans>50 km/s) at the surfaces of the secondaries. Most of the emission lines in the spectra of these objects are formed under conditions close to thermalization, enabling modeling of their pro files in an LTE approximation. A strong λ3905 Å emission line has been identified as the 3s²3p4s 1P⁰-3s²3p² 1S SiI λ3905.52 Å line formed in the atmosphere of the hot spot. The observed intensity can be explained by non-LTE “superionization” of SiI atoms by soft UV radiation from the white dwarf. We suggest a technique for identifying binaries whose cool components are subject to UV irradiation based on observations of λ3905 Å emission in their spectra.     

Multifrequency studies of massive cores with complex spatial and kinematic structures

Five regions of massive-star formation have been observed in various molecular lines in the frequency range～85?89 GHz. The studied regions comprise dense cores, which host young stellar objects. The physical parameters of the cores are estimated, including the kinetic temperatures (～20?40 K), the sizes of the emitting regions (～0.1?0.6 pc), and the virial masses (～40?500 M_⊙). The column densities and abundances of various molecules are calculated assuming Local Thermodynamical Equilibrium(LTE). The core in 99.982+4.17, which is associated with the weakest IRAS source, is characterized by reduced molecular abundances. The molecular line widths decrease with increasing distance from the core centers (b). For b ? 0.1 pc, the dependences ΔV (b) are close to power laws (∝b^?p), where p varies from ~0.2 to ~0.5, depending on the object. In four cores, the asymmetries of the optically thick HCN(1–0) and HCO⁺(1–0) lines indicates systematicmotions along the line of sight: collapse in two cores and expansion in two others. Approximate estimates of the accretion rates in the collapsing cores indicate that the forming stars have masses exceeding the solar mass.     

A method for modeling the formation of caii lines in the spectra of irradiated stellar atmospheres

We have developed a method for calculating deviations from LTE of level populations and profiles of selected spectral lines in stellar atmospheres in the presence of external radiation. The influence of Thomson scattering at the frequencies of the external radiation is considered. The method used to calculate model irradiated atmospheres in a semi-grey approximation has been improved. We have modified the NONLTE3 code used to determine the level populations to make it suitable for irradiated atmospheres. A model for the CaII atom including 42 energy levels of CaII, the ground state of CaIII, and 80 linearized transitions was constructed for these calculations. This atomic model takes into account the effect of all relevant collisional processes and radiative processes at the frequencies of the internal and external radiation. We investigated the correctness of the non-LTE calculations for the CaII ion by analyzing 16 lines of ionized calcium in the solar spectrum. The influence of uncertainties in the atomic data on the non-LTE level populations and CaII line profiles was also analyzed, and the van der Waals broadening coefficients C ₆ were refined. The scaling coefficient in the Dravin formula was taken to be 0.1. We found the non-LTE abundance corrections for most lines to be significant (Δlog?(Ca)=0.05?0.15dex), even under the conditions for the solar atmosphere. The lines of the λ=8498, 8542, 8662 Å infrared triplet can be adequately described. Differences in the mean calcium abundance obtained using different model atmospheres are smaller than 0.02 dex. Our final estimate of the mean calcium abundance in the solar atmosphere is log?(Ca)=6.31, in good agreement with the meteoritic abundance, log?(Ca)=6.32.     

Effects of spot structure of lines of rare earths and non-LTE effects on lithium abundance estimates for two roAp stars

Taking into account blending of the lithium 6108 Å line profile by adjacent rare-earth lines together with their spotted surface structure does not appreciably affect lithium abundance estimates for the atmospheres of HD 83368 and HD 60435 but provides a better fit of the observed and stimulated line profiles. Our computed non-LTE corrections reduce the lithium abundance estimates by 0.1–0.2 dex for both stars. Given the uncertainties in the lithium abundances, it is not possible to be certain whether the lithium abundances in roAp stars, or at least in their spots, exceed the cosmic (primordial) value.     

Ivsite,Na<Subscript>3</Subscript>H(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>, a new mineral from volcanic exhalations of fumaroles of the Fissure Tolbachik Eruption of the 50th Anniversary of the Institute of Volcanology and Seismology,Far East Branch,Russian Academy of Sciences

Fine-granular (<0.1 mm) flattened colorless transparent crystals of ivsite form white aggregates. The empirical formula (Na_2.793Cu_0.056)_2.849HS_2.016O₈ is close to the ideal Na₃H(SO₄)₂. The structure was refined up to R = 0.040. Ivsite has a monoclinic symmetry, P2₁/c, a = 8.655(1) Å, b = 9.652(1) Å, c = 9.147(1) Å, β = 108.76(1)°, V = 723.61(1) ų, Z = 4. Na atoms occur at six- and seven-fold sites (NaO₆ and NaO₇); S atoms, in isolated SO₄ tetrahedrons; these polyhedrons form a three-dimensional framework. The diagnostic lines of powder diffraction patterns (d[Å]–I–hkl) are 4.010–53–12-1, 3.949–87–012, 3.768–100–210, 3.610–21–20-2, 3.022–22–031, 2.891–42–22-2, 2.764–49–31-1, and 2.732–70–13-1.     

Hyperfine Splitting in the VALD Database of Spectral-line Parameters

The Vienna Atomic Line Database (VALD) has been supplemented with new data and new functionality—the possibility of taking into account the effect of hyperfine splitting (HFS) of atomic levels in the analysis of line profiles. This has been done through the creation of an ancillary SQL database with the HFS constants for atomic levels of 58 isotopes of 30 neutral and singly-ionized atoms. The completeness of the collected data and new opportunities for studies of stars of various spectral types is analyzed. The database enables analysis of splitting of up to 60% of lines with measurable effects in the ultraviolet (λ ≳ 1000 Å ), and up to 100% of such lines in the optical and infrared ranges (λ ≲ 25 000 Å ) for A–M stars. In the spectra of hot O–B stars, it is necessary to use laboratory measurements for atoms in the second and higher stages of ionization.

     

Dependence of the absorption-line profiles and radial-velocity curve of the optical star in an X-ray binary on the orbital inclination and component-mass ratio

Theoretical absorption-line profiles and radial-velocity curves for tidally deformed optical stars in X-ray binary systems are calculated assuming LTE. The variations in the profile shapes and radial-velocity curve of the optical star are analyzed as a function of the orbital inclination of the X-ray binary system. The dependence of the shape of the radial-velocity curve on the orbital inclination i increases with decreasing component-mass ratio q = m _x /m _v . The integrated line profiles and radial-velocity curves of the optical star are calculated for the Cyg X-1 binary, which are then used to estimate the orbital inclination and mass of the relativistic object: i < 43° andm _x = 8.2–12.8 M_⊙. These estimates are in good agreement with earlier results of fitting the radial-velocity curve of Cyg X-1 using a simpler model (i < 45°, m _x = 9.0–13.2 M_⊙).     

A many-year photometric and spectroscopic variability study of planetary nebulae (1968–2008). The young planetary nebula IC 4997

We present the results of our many-year (1968–2008) photoelectric photometry and absolute spectrophotometry of the young variable planetary nebula IC 4997, performed in uniform systems. Integrated line energy fluxes in the range 3727–5007 Å are tabulated, along with the integrated (star + nebula) continuum flux at 4500 Å, and time variations investigated. We study the time behavior of fluxes in the hydrogen, HeI, [OIII], [OII], [NeIII] emission lines. Variations of the line intensity ratio R = F([OIII]4363 Å)/F(Hγ) between 1938 and 2008 are presented. We estimate the nebula’s electron density N _e and electron temperature T _e for 1972–1992: the mean nebula N _e increased by the factor of five, from ～4 × 10⁵ to ～2 × 10⁶ cm^?3, while the mean T _e increased from 12 000 to 14 000 K. The color temperature of the exciting star, measured from the 4000–4900 Å continuum, increased from 37 000–40 000 K to 47 000 K during the time interval covered by our observations, as is confirmed by the growth of ionization of HeI, NeIII, and OIII (from the 4363 Å line). V-band variations of the object’s integrated (nebula + star) light with an amplitude about 0.5 ^m can essentially be fully explained as being due to changing contributions from variable fluxes in the [OIII] 5007 and 4959 Å lines. The V magnitude in 2009 (after 40 years) happened to be the same as at the start of our observations in 1968. A period of the order of 50 years can also be noted in log R(t). This may provide evidence for binarity of the central star and be related to its orbital period.     

Lithium abundances in sunspots from observations made in 2014

Spectra of sunspots in the regions of the Li I 6708 Å line and certain Fe I and Ca I lines are presented. The observations wee carried out in August 2014 using a CCD array mounted at the BST-2 telescope of the Crimean Astrophysical Observatory. Sunspot models based on the observed Fe I and Ca I line profiles have been computed, and used together with the observed Li I 6708 Å profiles to determine the lithium abundances. The mean lithium abundance for the sunspots observed on August 26, 2014 is logA(Li) = 1.2 (on a scale for which logA(H) = 12.0). Sunspot spectra obtained on October 8, 2011 were also analyzed, yielding logA(Li) = 1.02.