Stars with discrepant <Emphasis Type="Italic">v</Emphasis> sin <Emphasis Type="Italic">i</Emphasis> as derived from the Ca II λ3933 Å and Mg II λ4481 Å lines. V. HD 182255 and HD 214923—SPB stars in binary systems

The axial rotation of a star plays an important role in its evolution, the physical conditions in its atmosphere and the appearance of its spectrum.We analyzed the CCD spectra of two stars for which their projected rotational velocity differs remarkably when derived from Ca II λ3933 Å and Mg II λ4481 Å lines. We estimated the projected rotational velocity of HD182255 to be 15.5 kms^?1, although in various spectra of this star the line widths correspond to values as high as 28.5 km s^?1. We found the HeI λ4471.498 Å line to be shifted to longer wavelengths by 0.046 Å, thus indicating a presence of the ³He I isotope in the atmosphere of this star with the ³He : ⁴He ratio from 0.2 to 0.6.We also found an absorption feature at the position of the forbidden line He I λ4470.02Å. We found the lines ofMg II and CII originating from higher excited levels to be missing in the spectra of HD 182255. For HD 214923 we determined the projected rotational velocity v sin i = 165km s^?1 from the profiles of the metallic lines and Ca II λ3933Å, whereas for helium lines v sin i ≈ 130km s^?1 is more appropriate. Radial velocity analysis results in three long periods of ≈ 105, 34, and 15 days, and a short period of ≈ 22 hours, close to the pulsational one mentioned earlier in the literature.     

Stars with discrepant <Emphasis Type="Italic">v</Emphasis> sin <Emphasis Type="Italic">i</Emphasis> as derived from the Ca II 3933 and Mg II 4481 Å lines. VI. HD 199892 — an SB2 spectroscopic binary

We analyzed the spectra of a well known SB1 binary HD199892 for which the projected rotational velocity v sin i, introduced in the literature, significantly differs when determined from the lines of Ca II at 3933 Å and ofMg II at 4481 Å. Contrary to the former findings, we discovered the signs of spectral lines of a companion star in the profile of Hβ as well as weak metallic lines in the high resolution high S/N spectra covering the most of the visual region. We estimated the secondary star to be a main sequence A4V star with a mass of 2.2M _⊙ and derived its radial velocity which resulted in the mass of the primary M = 4.6M _⊙. Short sections of the spectra in the Mg II 4481 Å and Ca II 3933 Å regions are analyzed as well.     

Stars with discrepant <Emphasis Type="Italic">υ</Emphasis> sin <Emphasis Type="Italic">i</Emphasis> as derived from Ca II 3933 and Mg II 4481 Å lines. II. Multiple star HD 90569

Axial rotation of a star plays an important role in its evolution, physical condition in its atmosphere and appearance of its spectrum. Methods of determinations of υ sin i are based on comparison of the observed profiles of spectral lines with theoretical ones. Their accuracy depends on the kind and quality of spectrograms as well as on the algorithms used. A frequently used method is the simple comparing of one line, e.g. the Ca II at 3933 Å or Mg ii at 4481 Å. This however, may result in a false value of υ sin i if low dispersion spectra are used. In this work we studied contemporary CCD as well as older photographic spectra of the multiple star HD90569. We determined the projected rotational velocity value to be υ sin i = 11 km/s. Besides formerly reported enhancing of lines of Cr, Fe, Mn and Sr, we found also large overabundances of rare earths, gallium and platinum. Helium, carbon, nitrogen, oxygen, aluminium, calcium, scandium and nickel are in deficit. The spectrum of the occultation double was not identified to be of the SB2-type, however, there are some observable evidences that the pair creates a binary with a long orbital period. Despite this there are also observations that leave such interpretation uncertain.     

Reanalysis of two eclipsing binaries: <Emphasis Type="Italic">EE</Emphasis> <Emphasis Type="Italic">Aqr</Emphasis> and <Emphasis Type="Italic">Z</Emphasis> <Emphasis Type="Italic">Vul</Emphasis>

We study the radial-velocity and light curves of the two eclipsing binaries EE Aqr and Z Vul. Using the latest version of the Wilson and Van Hamme (Computing Binary Star Observables, 2003) model, absolute parameters for the systems are determined. We find that EE Aqr and Z Vul are near-contact and semi-detached systems, respectively. The primary component of EE Aqr fills about 96% of its ‘Roche lobe’, while its secondary one appears close to completely filling this limiting volume. In a similar way, we find fill-out proportions of about 72 and 100% of these volumes for the primary and secondary components of Z Vul respectively. We compare our results with those of previous authors.     

Stars with discrepant v sin i as derived from Ca II λ 3933 Å and Mg II λ 4481 Å lines. III. Stars with v sin i (λ 3933 Å) < v sin i (λ 4481 Å)

Axial rotation of a star plays an important role in its evolution, physical conditions in its atmosphere and the appearance of its spectrum. We analyzed CCD spectra of nine stars for which the projected rotational velocity derived from the Ca II line at λ 3933 Å was remarkably lower than the one derived from the MgII line at λ 4481 Å. We derived effective temperatures and surface gravities using published uvbyβ photometries, and computed synthetic spectra. Comparing the observed line profiles of the two lines with the computed ones, we estimated the values of v sin i. One of the stars, HD44783, is a Be-star which, besides the narrow absorptions in the spectrum originating in its circumstellar envelope, also has lines of interstellar origin. We also found indications of circumstellar matter in the spectrum of HD25152. In the spectra of the remaining seven stars the narrow components in the Ca II λ 3933 Å line as well as narrow absorptions in the Na I λ 5889.951 Å (D1) and λ 5895.924 Å (D2) lines are of interstellar origin. In HD114376 there are two systems of interstellar components, thus disclosing two different interstellar clouds in the direction of the star. In the spectrum of HD138527 signs of a possible companion were detected, the emission of which contributes 15% to the total light of the system.     

The Na <Emphasis Type="SmallCaps">i</Emphasis> and Sr <Emphasis Type="SmallCaps">ii</Emphasis> Resonance Lines in Solar Prominences

We estimate the electron density, \(n_{\mathrm{e}}\), and its spatial variation in quiescent prominences from the observed emission ratio of the resonance lines Na?i?5890 Å (D₂) and Sr?ii?4078 Å. For a bright prominence (\(\tau_{\alpha}\approx25\)) we obtain a mean \(n_{\mathrm{e}}\approx2\times10^{10}~\mbox{cm}^{-3}\); for a faint one (\(\tau _{\alpha }\approx4\)) \(n_{\mathrm{e}}\approx4\times10^{10}~\mbox{cm}^{-3}\) on two consecutive days with moderate internal fluctuation and no systematic variation with height above the solar limb. The thermal and non-thermal contributions to the line broadening, \(T_{\mathrm{kin}}\) and \(V_{\mathrm{nth}}\), required to deduce \(n_{\mathrm{e}}\) from the emission ratio Na?i/Sr?ii cannot be unambiguously determined from observed widths of lines from atoms of different mass. The reduced widths, \(\Delta\lambda_{\mathrm{D}}/\lambda_{0}\), of Sr?ii?4078 Å show an excess over those from Na?D₂ and \(\mbox{H}\delta\,4101\) Å, assuming the same \(T_{\mathrm{kin}}\) and \(V_{\mathrm{nth}}\). We attribute this excess broadening to higher non-thermal broadening induced by interaction of ions with the prominence magnetic field. This is suggested by the finding of higher macro-shifts of Sr?ii?4078 Å as compared to those from Na?D₂.     

Sensitivity of Selected Ba <Emphasis Type="SmallCaps">ii</Emphasis>, Fe <Emphasis Type="SmallCaps">i</Emphasis>, Fe <Emphasis Type="SmallCaps">ii</Emphasis>, and Cr <Emphasis Type="SmallCaps">i</Emphasis> Spectral Lines to Velocity in Quiet Solar Atmosphere

We examine the sensitivity of selected Ba?ii, Fe?i, Fe?ii, and Cr?i spectral lines to changes of the line-of-sight velocity by sharpness of their line profiles and response functions to line-of-sight velocity evaluated by the 1-D model of the quiet solar atmosphere in the LTE approximation. The set of selected lines includes the Ba?ii 4554 Å line, generally considered to be an excellent Doppler mapper. Our findings confirm earlier results showing that the sensitivity increases not only with wavelength, as anticipated from the Doppler relation, but mainly with the sharpness of line profiles given by the ratio of their depths and widths. The line Fe?i 5247 Å is the most sensitive in our set, whereas the Fe?i and Fe?ii infrared lines show very low sensitivity because of their large thermal widths. The line Ba?ii 4554 Å shows only moderate sensitivity due to its large width, given by a broad hyperfine structure and isotopic split. For the first time we identify a very promising and so far unknown Doppler mapper of the solar photosphere and low chromosphere, which is the line Ba?ii 6497 Å. Its sensitivity is comparable with the sensitivity of Fe?i 5247 Å and clearly surpasses the sensitivity of Ba?ii 4554 Å. The line Ba?ii 6497 Å offers many advantages, making it a highly recommendable choice for future studies of line-of-sight velocities in the photosphere and low chromosphere.     

Study of the non-stationarity of the atmosphere of <Emphasis Type="Italic">κ</Emphasis> Cas. Ii. Variability of the H<Emphasis Type="Italic">γ</Emphasis>, H<Emphasis Type="Italic">β</Emphasis>, and H<Emphasis Type="Italic">α</Emphasis> wind-line profiles

We study the variability of the Hγ, Hβ, and Hα line profiles in the spectrum of the supergiant κ Cas. The variability pattern proved to be the same for all the lines considered: their profiles are superimposed by blueshifted, central, and redshifted emission. For Hγ the positions of the emissions coincide with the positions of the corresponding emissions for He I λλ 5876, 6678 Å lines, and are equal to about ?135 ± 30.0 km s^?1, ?20 ± 20 kms^?1, and 135 ± 30.0 kms^?1, respectively, whereas the three emissions in the Hβ profiles are fixed at about ?170.0 ± 70.0 kms^?1, 20 ± 30 kms^?1, and 170.0 ± 70.0 km s^?1, respectively. The positions of the blueshifted and central emissions for Hα are the same as for Hβ, with additional blueshifted emission at ?135.0 ± 30.0 kms^?1, whereas no traces of emission can be seen in the red wing of the line. These emissions show up more conspicuously in wind lines, however, their traces can be seen in all photospheric lines. When passing from wind lines to photospheric lines the intensity of superimposed emission components decreases and the same is true for the absolute values of their positions in line wings expressed in terms of radial velocities. The V/R variations of the lines studied found in the spectrum of κ Cas and the variability of the Hα emission indicate that the star is a supergiant showing Be phenomenon.     

Existence of wormhole solutions and energy conditions in <Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">R</Emphasis>, <Emphasis Type="Italic">T</Emphasis>) gravity

This paper is devoted to investigate the spherically symmetric wormhole models in f(R, T) gravity, where T and R are trace of stress energy tensor and the Ricci scalar, respectively. In this context, we discuss three distinct cases of fluid distributions viz, anisotropic, barotropic and isotropic matter contents. After considering the exponential f(R, T) model, the behavior of energy conditions are analyzed that will help us to explore the general conditions for wormhole geometries in this gravity. It is inferred that the usual matter in the throat could obey the energy conditions but the gravitational field emerging from higher order terms of modified gravity favor the existence of the non-standard geometries of wormholes. The stability as well as the existence of wormholes are also analyzed in this theory.     

Determination of the combination of cosmological parameters Ω<Subscript><Emphasis Type="Italic">m</Emphasis></Subscript><Superscript><Emphasis Type="Italic">α</Emphasis></Superscript><Emphasis Type="Italic">σ</Emphasis><Subscript>8</Subscript>

We have obtained new constraints on the cosmological parameters Ω _m and σ ₈ from the peculiar velocities of flat edge-on spiral galaxies from the RFGC catalog. Based on these results presented graphically, we have found the quantitative condition (Ω _m /0.3)^0.37 σ ₈ = 0.92 ± 0.05. The estimates of Ω _m and σ ₈, along with their combinations Ω _m ^α σ ₈ for various α, are compared with the estimates by other authors.     

Stars with discrepant v sin i as derived from Ca II 3933 and Mg II 4481 Å lines. I. Composite-spectrum star HD 2913

Axial rotation of a star plays an important role in its evolution, physical conditions in its atmosphere and the shape of its spectrum. Methods of determining of v sin i are based on comparison of the observed profiles of spectral lines with the theoretical ones. Their accuracy depends on the type and quality of spectrograms, as well as on the algorithms used. A frequently used method is a simple comparison of one line, e.g. the Ca ii at 3933 Å or Mg ii at 4481 Å. This, however, may result in a false value of v sin i in case when low-dispersion spectra are used. We investigate the spectra of stars with a significant discrepancy of their rotational velocities introduced in various sources, and analyze the corresponding spectral region from the point of view of possible admixed features, which may mask the true line profiles. We use CCD spectra of the stars having this discrepancy, to compare with theoretical spectra. We also studied photographic spectra, obtained during the 1970s and 1980s. In this work we studied the spectra of the binary HD 2913A, and identified the spectrum of its weaker component designated as “Ab”. We estimated the effective temperature, surface gravity and projected rotational velocity of the weaker component that classify it as an early F-type Main Sequence star. The discrepancy between the values of v sin i derived from the two lines of calcium and magnesium is explained as a consequence of superposition of the pair’s spectra. The cooler component contributes by a strong Ca ii-K line, and thus significantly broadens the observed line profile.     

Nonstationarity of the atmosphere of <Emphasis Type="Italic">α</Emphasis> Cyg: II. Variability of the ion and H<Emphasis Type="Italic">β</Emphasis> line profiles

We report an efficient method for analyzing the radial-velocity and line-profile variability. We show that a detailed analysis of the variations of line profiles and velocity field in the stellar atmosphere requires the radial velocities to be measured separately for the blue and red halves of the absorption lines at different levels of their residual intensity. We applied this method to 120 CCD spectra taken in 1998–99 with the coude echelle spectrograph attached to the 2-m telescope of Shemakha Astronomical Observatory of National Academy of Sciences of Azerbaijan and analyzed the variations of the radial velocities and profiles of ion and Hβ lines in the spectrum of α Cyg. In the case of ion lines both halves of the absorption profile exhibit synchronous radial-velocity variations at all levels of line intensity. In the case of the Hβ line, which forms in the layers where stellar wind originates, the pattern of radial-velocity variations differs for the blue and red halves of the absorption profile. The variability pattern is the same at all levels in the red half of the profile, the blue half of the profile exhibits different variability patterns at different levels of residual line intensity. Identification and analysis of such variations allows us to study the nature of stellar-wind variability in the region of wind formation.The spectrum of α Cyg showed no line-profile or radial-velocity variations for six days in both halves of the absorption contour at all levels of line intensity. The star was in the quiescent phase.     

Families <Emphasis Type="Italic">c</Emphasis> and <Emphasis Type="Italic">i</Emphasis> of periodic solutions of the restricted problem for μ = 5 × 10<Superscript>−5</Superscript>

We consider the circular planar restricted three-body problem with the mass parameter μ = 5 × 10^?5. Two families of periodic solutions are calculated: family c, starting from the collinear fixed point L ₁, and the initial part of familyi, which begins by direct circular orbits of an infinitely small radius around the body of bigger mass. The calculated families are very close to the generating ones, which we described earlier. In particular, the existence of the predicted zigzag structure of characteristics of family iis verified. New properties of the planar and vertical traces are discovered.     

Orbit Orientation of the Planet in <Emphasis Type="Italic">τ</Emphasis> Boo (HD 120136)

We determined the rotation period and the parameters of the global magnetic field of τ Boo. This allowed us to estimate the inclination of the rotational axis of the star to the line of sight, as well as to obtain estimates of the inclination of the planet’s orbital plane to the stellar equator.     

Quintessence cosmology with a traversable wormhole,massive decaying gravitons and with varying <Emphasis Type="Italic">G</Emphasis> and <Emphasis Type="Italic">Λ</Emphasis>

In this work, we explore many cosmological implications of a four-dimensional cosmology dominated by quintessence with a static traversable wormhole, spatio-temporal varying G and by taking into account a decaying cosmological constant and a decaying graviton mass by means of an additional bimetric tensor in Einstein’s field equations proposed by Visser in 1998.     

Oscillations Accompanying a He <Emphasis Type="SmallCaps">i</Emphasis> 10830 Å Negative Flare in a Solar Facula

On 21 September 2012, we carried out spectral observations of a solar facula in the Si?i 10827 Å, He?i 10830 Å, and H\(\upalpha\) spectral lines. Later, in the process of analyzing the data, we found a small-scale flare in the middle of the time series. Based on the anomalous increase in the absorption of the He?i 10830 Å line, we identified this flare as a negative flare.The aim of this article is to study the influence of the negative flare on the oscillation characteristics in the facular photosphere and chromosphere.We measured the line-of-sight (LOS) velocity and intensity of all the three lines as well as the half-width of the chromospheric lines. We also used the Helioseismic and Magnetic Imager (HMI) magnetic field data. The flare caused a modulation of all these parameters. In the location of the negative flare, the amplitude of the oscillations increased four times on average. In the adjacent magnetic field local maxima, the chromospheric LOS velocity oscillations appreciably decreased during the flare. The facular region oscillated as a whole with a 5-minute period before the flare, and this synchronicity was disrupted after the flare. The flare changed the spectral composition of the LOS magnetic field oscillations, causing an increase in the low-frequency oscillation power.     

From the <Emphasis Type="Italic">Vega</Emphasis> mission to comet Halley to the <Emphasis Type="Italic">Rosetta</Emphasis> mission to comet 67/P Churyumov–Gerasimenko

The data acquired by the Vega and Giotto spacecraft, while investigating comet 1Р/Halley in 1986, are compared to the results of the first phase of exploration of the nucleus of comet 67P/Churyumov–Gerasimenko performed with the Rosetta and Philae modules. The course of the Rosetta mission activity and the status of the modules after the Philae probe landing on the comet’s nucleus are overviewed. Since some elements of the touchdown equipment failed, a number of in-situ experiments on the comet’s nucleus were not carried out.     

Short-Term H <Emphasis Type="Italic">α</Emphasis> Line Variations in Classical Be Stars: 59 Cyg and OT Gem

We present the optical spectroscopic study of two classical Be stars, 59 Cyg and OT Gem obtained over a period of few months in 2009. We detected a rare triple-peak H α emission phase in 59 Cyg and a rapid decrease in the emission strength of H α in OT Gem, which are used to understand their circumstellar disks. We find that 59 Cyg is likely to be rapid rotator, rotating at a fractional critical rotation of ～0.80. The radius of the H α emission region for 59 Cyg is estimated to be R _d/R _? ～ 10.0, assuming a Keplerian disk, suggesting that it has a large disk. We classify stars which have shown triple-peaks into two groups and find that the triple-peak emission in 59 Cyg is similar to ζ Tau. OT Gem is found to have a fractional critical rotation of ～0.30, suggesting that it is either a slow rotator or viewed in low inclination. In OT Gem, we observed a large reduction in the radius of the H α emission region from ～6.9 to ～1.7 in a period of three months, along with the reduction in the emission strength. Our observations suggest that the disk is lost from outside to inside during this disk loss phase in OT Gem.     

Statistics of interacting galaxies at <Emphasis Type="Italic">z</Emphasis> ∼ 0.7

We present the results of our analysis of the frequencies of galaxies with tidal tails and M51-type galaxies in several deep fields of the Hubble Space Telescope (HDF-N, HDF-S, HUDF, GOODS, GEMS). In total, we have found about seven hundred interacting galaxies at redshifts z ≤ 1.5 in these fields. At z ≤ 0.7, the observed space densities of galaxies with tidal structures and M51-type galaxies have been found to increase as ∝(1 + z) ^m , where m ≈ 2.6. According to our estimates, over the last 6–7 Gyr, i.e., at z ≤ 0.7, about a third of the galaxies with M(B) ≤ −18 ^m must have undergone strong gravitational perturbations and mergers and ∼1/10−1/5 of the galaxies have swallowed relatively low-mass nearby satellites typical of M51-type galaxies. The possible decrease in the time scale on which a distant galaxy appears peculiar with growing z can increase considerably the estimated rate of mergers.     

Radio identification of decameter-wave sources. II: The 30°< <Emphasis Type="Italic">δ</Emphasis> <40° declination interval

This paper is dedicated to the identification of decameter-wave sources of the UTR catalog within declination interval 30°< δ <40°. UTR sources are cross-identified with CATS database catalogs within 40′ × 40′ error boxes. The sources are deblended using the data on the coordinates of the objects and the behavior of their continuum radio spectra. The spectra of 875 sources are derived and fitted by standard analytical functions. Of these sources, 221 objects have straight-line spectra with spectral indices α < ?1.0. All objects are catalogued and stored in the CATS database.