Scanner observations of comet P/Crommelin 18181

Spectral scans of the coma of comet P/Crommelin 1818. I have been obtained in the wavelength range 3200–6500 Å. Strong emission features of CN(3883 Å) and C₂ Swan bands (4695, 5165, and 5538 Å) have been identified. Some weak emission features of CH(3890 Å), C₃(4050 Å), CN(4200 »), and C₂ + CH(4358 ») were also detected. Sodium was found to be absent in this comet. An estimate of CN and C₂ abundances has been made and their production rate have been derived.     

Spectrophotometry of comet Hartley-Good (1985l)

We present spectrophotometric studies of comet Hartley-Good (1985l) in the spectral region 3200–7000 Å. The emission features of molecules CN, CH, C₂, and C₃ are observed. The variation of the emission strength of different species has been studied as a function of heliocentric distance. The abundances (N) and production rates (Q) of the molecules are also estimated.     

Distribution of polarization and intensity of radiation across the stellar disk and numberical values of atmospheric characteristics governing this distribution

Computations of polarization and intensity of radiation from a unit stellar surface area are presented, as well as a study of the numerical characteristics of atmospheres — single-scattering albedo and the initial source function(), which define the polarization behaviour of atmospheres. The radiatively stable models of stellar atmospheres presented by Kuruczet al. (1974) and Kurucz (1979) have been used for calculations. Since the versus optical depth dependence is rather weak, it has been assumed that (=cost. With a fixed effective temperatureT _eff maximum values of are characteristic of stars featuring the lowest surface gravity accelerationg. Among stars with radiatively stable atmospheres, maximum values of (=5000 Å) 0.4–0.6 are exhibited by supergiants withT _eff=8000–20 000 K. The plot of () is characterized by discontinuities at the boundaries of spectral series for hydrogen and, sometimes, for helium. Maximum are attained in the Lyman region of =912–1200 Å, where can reach the value 0.7–0.9 for supergiants, this value being 0.3 for Main-Sequence stars. For stars withT _eff 35 000 K, high values of also are attained for <912 Å. Within the infrared region, is always small because of bremsstrahlung absorption.A rapid growth of the source functionB with < typical for ultraviolet range (within the Wien part of spectrum), together with high values of results in the strong polarization of emission from a unit stellar surface element, sometimes exceeding the values for the case of a pure electron scattering. For longer wavelengths, where the limb-darkening coefficient is smaller, the plane of polarization abruptly turns 90° in the central parts of the visible stellar disk.     

Hydrogen and helium spectra in large magnetic fields

The energy levels and wave functions of hydrogen and helium atoms in the presence of large (10⁷G) magnetic fields are found by assuming that the eigenvalues and eigenvectors may be approximated by those of a truncated Hamiltonian matrix. In these atoms, fields of this size produce, in addition to the usual Paschen-Back effect, a quadratic Zeeman effect. This contributes an upward shift to the energy of all levels, which at sufficiently high fields dominates the Paschen-Back splitting.The behavior of a number of eigenvalues and wave functions as a function of magnetic field is presented. The effects of the field on the wavelengths and strengths of the components of H and the helium lines 4471, 4026 and 4120 as well as the forbidden 4025 are examined. In hydrogen the lines are split into components attributed to the now nondegenerate transitionsnlm _lnlm_l. In helium forbidden lines are excited, which may develop strengths larger than those of the allowed lines.     

Spectrophotometric observations of comet Hartley-Good (1985l)

Spectrophotometric observations of Cornet Hartley-Good (19851) during five nights in 1985 are presented in the wavelength range 3200–7000 ». The emission bands due to CN, CH, C₂, and C₃ molecules are observed. The abundances (N) and production rates (Q) of the molecules are derived.     

Spectrophotometry of Comet Bradfield (1980t) during post-perihelion period

Spectrum scans of the head of Comet Bradfield (1980t) covering the wavelength range 365–640 nm were made on two nights when the heliocentric distance of the comet varied from 0.55 to 0.58 AU. The emission features of the CN band at 388 nm and Swan band sequence of C₂ at 474 nm, 516 nm, and 563 nm are identified and absolute fluxes in these bands as well as in the continuum are derived. The continuum energy distribution curves of the comet have been compared with those of the Sun and the star Crv (G5 III). An estimate of the number of C₂ and CN molecules in the head of the comet has been made through the measured intensities of their respective bands lying in this region.     

A new type of a photoelectric magnetograph

The electro-optic deflector as an analyzer of circular polarization in the photoelectric magnetograph is described. The electro-optic deflector consists of an electro-optic crystal and a polarizing beamsplitter. The plane bifurcation of this beamsplitter coincides with the spectrograph dispersion direction. The beamsplitter bifurcates a spectral line in two components. The distance between them is ₀. The photometer slit is situated between these components. Both components of Zeeman splitting fall on the photometer slit but the distance between them varies from ₀ + 2 _H to ₀ – 2 _H (where _H is the Zeeman splitting) with the electric voltage frequency applied to the electro-optic crystal. The intensity variations at the photometer slit are proportional to 4 _H .     

Systemes hamiltoniens au voisinage d'une solution d'equilibre. II:Stabilité des solutions périodiques

Resume On étudie la stabilité des solutions périodiques d'un couplage de systèmes linéaires au voisinage de résonances. Les valeurs propres distinctes _k de la matrice du système linéaire non perturbé sont telles que _k–_j=iq pour tout couple [k, j]; i=–1, q est un nombre entier, la fréquence de la solution. Une application est faite pour un système à trois degrés de liberté au voisinage de la résonance 221.

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Hamiltonian systems in the neighbourhood of an equilibrium solution. II:The stability of periodic solutions

The stability of the periodic solutions for an Hamiltonian system is investigated. Here the distinct eigen values _k of the matrix of the unperturbated linear system are such that _k–_j=iq for any [k, j]; i=–1, q is an integer, is the frequency of the periodic solution. An application is made for a system with three degrees of freedom, near the resonance 221.

     

Intensity fluctuations in Fraunhofer lines

An expression is derived for the fluctuation (t) in emergent intensity (observed at some wavelength in a Fraunhofer line or the continuum) caused by a perturbation in temperature (z, t) in the Sun's atmosphere. If the contribution function for the observed intensity is single-peaked near z and if (z) and p(z) are not too rapidly varying, then (t) m (z , t)+N p(z , t) where m and N depend on the structure of the atmosphere. We compute M, N, and contribution functions for several values of and in the inner wings of the K line (13933 Caii).Presently on leave of absence from the Institute for Astronomy, Honolulu, Hawaii.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Fine structure in the inner corona observed at the 1970 eclipse

On the slit spectrogram obtained at the 1970 eclipse in Mexico, the intensities of four coronal lines (Nixiii 5116, Fexiv 5303, Fex 6374, and Nixv 6702) and the continuum were measured as a function of distance along the slit. It is found that there exist a lot of fine fluctuations both in the lines and in the continuum intensities superposed on a large scale formation. The correspondence of such fluctuations between the continuum and the lines is good, with the exception of the line 6374 which shows a peculiar fluctuation. It is shown that the intensities of the three lines 5116, 5303, and 6702 seem to be proportional to the square of the continuum intensity while the 6374 line intensity may be proportional to the fourth power or more.     

Observed oddities in the lines H,K, b and Hβ

We compare microphotometer intensity traces perpendicular to dispersion in simultaneous spectrograms of good spatial resolution traced at various 's in each of the lines. Cross correlations between the different traces show the following: (a) For each _K there is a corresponding _{b 1}at which the coefficient of correlation, r, is a maximum, usually > 0.8. (b) No such high correlations are found between H and H. (c) Comparison of traces in the continuum and at all observed 's in K, H, b₁, b₂ show a range of 's in each line over which r is very significantly negative, while H shows no such peculiarity.     

On the A-transform of the exponential integrals

In this paper, a technique of recursive analysis is developed for the integral transform A of the exponential integral functionsE _n which is denoted as _n (). The main result of this analysis enables us to establish a two-term recurrence formula for _n (0) and a three-term recurrence formula for _n (); 0. A computational algorithm based on these formulae is also constructed and its numerical results forn=2(1)25 are presented to 15-digit accuracy.     

Structure of sunspots

The sunspot models published so far do not reproduce the observed run of the umbral continuum intensities over the entire spectral range 0.5 < < 4 m. Moreover, in several previous models is the temperature gradient smaller than both the adiabatic and the radiative equilibrium gradient.Agreement between intensities computed from acceptable models and measured intensities can be obtained by introducing an additional opacity for 0.8 m, which is probably caused by the crowding of atomic and molecular lines. We present a new umbral model atmosphere with a wavelength dependent opacity enhancement factor which explains the continuum intensities and also reproduces plausible center-to-limb variations and line profiles. This model is in radiative equilibrium down to _0.5 = 1.5, with an effective temperature of 4000 ± 100K. For the deeper superadiabatic layers a small but probably significant departure from radiative equilibrium is indicated by the intensities in the range 1.5 < < 2.4 m.The uncertainties in the present model and the effect of the additional opacity on line profiles are briefly discussed.     

Grain size dependence of far-infrared extinction spectra of amorphous fine grains

The far-infrared extinction spectra of fused silica grains with the size range from 1.8 m to 60 Å were measured. The spectra depend clearly on the grain size. For large grain sizes (from 1.8 m to 400 Å) the spectra show almost the ^–2 dependence ( is the wavelength), which resembles that of the bulk material. For fine grains (70 and 60 Å) the spectra are less steep, the wavelength dependence being ^–1. This grain size dependence of extinction spectra agrees essentially with the prediction of Seki and Yamamoto.     

The ionization mechanism in low level emission galaxy nuclei: Shocks

We analyze the emission component of galaxy nuclei at very low intensity levels (W(H)2Å). This emission level is considerably lower than that of classical LINERS like NGC 1052. We have access to weaker emission lines by averaging spectra with similar line ratios for H [NII], and [SII]. From the resulting spectrum for very low level emission nuclei, the [SII] 6717, 6731/[SIII] 9069, 9532 line ratio criterion (Diazet al., 1985a) unambiguously shows that shock-wave heating is the mechanism responsible for the ionization in such objects.     

Correlations between statistical population indices and spectral characteristics of carbon stars

The coefficients of correlation between spectroscopic data published by Yamashita (1967) and others for carbon stars and the statistical population indices calculated for these stars at the Toru Observatory are calculated (Table II). The intensity estimates of Cai 4227 Å, Nai D lines, the C¹³/C¹² ratio, then=n(Li/Ca) index, as well as CN and probably C₂ bands are higher in population I carbon stars. The CH(G) band and probably hydrogen (H, H, H) lines as well as Baii 4554 and 4934 Å lines are stronger in population II carbon stars. The photoelectric colour indices, corrected for interstellar reddening do not show significant population effects. They can be used as spectral type equivalents. For a population criterion the CH/CN intensity ratio is proposed.     

Les raies du triplet de l'helium de la Nova Delphini 1967

The aim of this paper has been to study the neutral helium triplet emission lines identified in the spectrum of the envelope of Nova Delphini. By comparing the observed flux of the neutral helium lines with that calculated theoretically by Robbins, we find that the optical thickness in the center of the line 3889 is of the order of 21.50 for summer 1969. The optical thickness obtained by this method is here denoted _tran(3889).On the other hand, we obtain the number of neutral helium atoms in the 2³S state [N(2³S)] by considering the equilibrium between the mechanisms that populate and depopulate this state. We then find that the depopulation by photoionization due to the radiation of Ly (Hi), transitions to the 2¹S, 2¹p and 2³p states by electron collision, photoionization due to the continuum radiation of the central star, are 82.70%, 13.20%, 2.40%, 0.90% and 0.80% respectively. We find that the mechanism of the photoionization by Ly is the dominant mechanism of depopulation of 2³S state. We calculated ( 3889) of the order of 82.37, fromN(2³S), obtained in the preceding paragraph. The optical thickness obtained by this method is here denoted _bal(3889).The difference between _tran(3889) and _bal(3889) is very large and it cannot be attributed to calculation errors. We have considered all the mechanisms that can depopulate the 2³S state, so we then conclude that the difference between _tran(3889) and _bal(3889) is due to the heterogeneity of the envelope of the Nova, already found by us in our previous study of the profiles of the permitted and forbidden lines. Finally, we find from this study a filling factor of the order of 0.30.     

Variability of the spectrum of β CrB in the region of the lithium line Li I λ6708Å

Some results of observations of the spectrum of the spectroscopic-binary Ap star CrB in the region of the lithium line Li I 6708Å are presented. The observations were made at the Crimean Astrophysical Observatory over the period 1993–1995 with the coudé spectrograph equipped with a CCD camera on the 2.6-m telescope. Several factors which can affect the behavior of the lithium blend are examined: stellar rotation, magnetic field, isotopic shift, the binary system, and blending by unidentified elements. The principal result of this work is the detection of variability of the lithium blend Li I 6708Å over the period of rotation of the star. The variations of the radial velocity V_r, and the FWHM of the lithium blend are reported here for the first time. They indicate either a nonuniform distribution of lithium or a nonuniform distribution of conditions for excitation of the lithium resonance doublet in the complex structure of the strong surface magnetic field. Similar variations are also shown by the lines of the rare-earth elements Gd II 6702.10 Å, Gd II + Ce II 6704.3Å, and Ce II + Fe I 6706.0 Å.Translated fromAstrofizika, Vol. 39, No. 1, pp. 19–30, January–March, 1996.     

Scanner observations of the Be starsν Gem,κ Ori,β Mon andω CMa

The photoelectric spectrophotometric scans of the Be stars Gem, Ori, Mon and CMa have been analyzed to find out few stellar parameters. The absolute energy distributions of these stars in the wavelength range 350–750 nm have been given. Their effective temperatures and gravities have been estimated from comparisons with non-LTE model atmospheres. The stars Gem and Mon have been found to have Balmer discontinuities in emission. The excess emission in the region 620–750 nm has been observed for Mon and CMa. The evolutionary aspects of these stars are discussed and their masses have been estimated.     

Ionized helium in prominences and in the chromosphere

Quiescent prominences It is found that Heii 4686 is emitted in the same cold region of 10000 K as hydrogen, metal and neutral helium emission lines. This conclusion is based on the finding that the observed width of 4686 is the same as the calculated width of 4686. The calculated width is derived from the observed widths of hydrogen and metallic lines. The large intensity of Heii 4686 in 10000 K can be explained by the ionization of Heii due to the UV radiation below 228 Å that comes from the corona and the transition region.Loop prominences The very broad width (30 to 50 km s^–1) of 4686 for two post-flare loop prominences shows that the Heii line is emitted in hot regions different from regions of hydrogen and metal emission. From the widths of the Balmer lines and many metallic lines the kinetic temperature for one loop is found to be 16000 K in one part and 7600 K in another part. The electron densities are 10^12.0 cm^–3 and less than 10^11.0 cm^–3 respectively.Chromosphere The intensity of 4686 in the chromosphere can be interpreted in terms of a temperature of 10000 K with the ionization due to UV radiation. But, since observations of the width of 4686 are not available, a definitive conclusion for the chromosphere cannot be reached.