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The paper presents observations of Ca(+) H, K, and infrared-triplet integrated line intensities, as well as H-beta, H-gamma and He 5876-A throughout eight quiescent prominences. The data were obtained with a multichannel coronal spectrophotometer system. The presently available theoretical models appear to be insufficient to provide a consistent basis for the interpretation of the data.
Tritium is measured as a function of depth in a Surveyor 3 sample. The upper limit for solar-wind-implanted tritium gives an H-3/H-1 limit for the solar wind of 10 to the -11th power. The temperature-release patterns of C-14 from lunar soils are measured. The C-14 release pattern from surface soils differs from a trench-bottom soil and gives positive evidence for the presence of C-14 in the solar wind with a C-14/H-1 ratio of approximately 6 by 10 to the -11th power. This C-14 content fixes a minimal magnitude for nuclear processes on the solar surface averaged over the past 10,000 yr. The H-3 and C-14 contents combine to require that either the mixing rate above the photosphere be rapid or that the H-3 produced by nuclear reactions be destroyed by secondary nuclear reactions before escaping in the solar wind.
The characteristics of 3.5-mm depression features associated with two 'disparation brusques' observed in H-alpha are discussed. The millimeter depressions still exist, although reduced in strength, after the disappearance of the H-alpha filament. The two depressions correspond to temperatures of 600 and 450 K before and to 200 and 250 K after the disappearance of the H-alpha filament.
If an atomic hydrogen/molecular hydrogen propellant containing at least 15% free H atoms by weight may be used, values for the theoretical specific impulse near and above 750 s may be predicted. The tritium-impregnation concept has been applied to manufacturing such an H/H2 propellant, and a phenomenological rate process theory has been derived for the matrix-isolation storage and equilibrium stability of atomic H produced at such ultralow temperatures in tritium-impregnated H2. It is suggested that an energy storage efficiency greater than 0.30 may be obtained at temperatures below 100 mK. So that the storage of atomic H is stable with respect to arbitrary small perturbations, the surface temperature must be less than a critical value dependent on sample volume, tritium weight fraction, and energy storage efficiency. A derivation of the formula for this critical surface temperature is presented, noting that the energy storage efficiency is to be fixed by experiment.
This paper presents and discusses far-infrared observations of nine H II regions within 1 deg of the galactic center, including Sgr A, Sgr B2, Sgr C, and G0.5-0.0. The far-infrared luminosity, color temperature, and optical depth of these regions and the ratio of infrared flux to radio-continuum flux lie in the range characteristic of spiral-arm H II regions. The far-infrared results are therefore consistent with the idea that the galactic-center H II regions are ionized by luminous early-type stars. Steep systematic gradients in far-infrared color temperature and optical depth are seen along the galactic plane between Sgr B2 and G0.5-0.0; the appearance of this area is similar to that of regions of star formation in the spiral arms.
Mg II h and k emission lines of the M2 giant beta Peg and the M5 supergiant alpha Her were detected in Copernicus observations. In the alpha Her profiles, similar to alpha Ori and alpha Sco profiles, the k line is asymmetric and the h line is symmetric. The possibility that the k line asymmetry is produced by overlying absorption is discussed. In beta Peg, both h and k lines are asymmetric, and line formation in an expanding chromosphere is indicated. The observations are in accord with one formulation of the Wilson-Bappu relation but deviate from another form of the Wilson-Bappu relation.
This paper presents interstellar H I column densities, mean H I space densities, total neutral hydrogen column densities, and total mean hydrogen space densities toward 100 stars surveyed in the L-alpha region with the U2 detector of the Copernicus satellite. The data for 47 stars are compared with OAO 2 results, and ratios of gas to E(B-V) color excess are computed for 30 'intercloud' stars, 45 'cloud' stars, and the combined sample of 75 stars. A definitive value of 5.8 x 10 to the 21st power atoms/sq cm per mag is obtained for the mean ratio of total neutral hydrogen to color excess, indicating that this ratio seems to be a constant, independent of location in the sky, except possibly toward stars with anomalous extinction. The anomalous ratio determined for Rho Oph is examined, and the galactic distribution of neutral hydrogen is evaluated. The following values are estimated for matter in the galactic plane within 500 pc of the sun: a total mean hydrogen space density of 1.15 atoms/cu cm, a mean H2 space density of 0.143 molecule/cu cm (possibly a lower limit), and a mean H I space density of 0.86 atom/cu cm (a possible overestimate).
Far-infrared emission has been measured from four Large Magellanic Cloud H II regions: the 30 Doradus nebula, MC75, MC76 and MC77. The far-infrared radiation is thermal emission from dust heated by starlight. The results show that the LMC H II regions, like H II regions in the Galaxy, have far-infrared luminosities comparable to the total luminosity of their exciting stars.
Contributions to the interstellar H I column density at high velocities from immediate postshock gas and from the cooling gas behind a shock are compared. The detection of high-velocity H I in L-epsilon and L-delta for Iota Ori is reported and interpreted as cooling gas behind a shock of 100 km/s velocity. The immediate postshock gas should be observable for shock velocities greater than 200 km/s and permits direct determination of the velocities of adiabatic shocks in the interstellar medium. It is pointed out that interstellar L-alpha and L-beta lines may not have purely Lorentzian profiles if high-velocity H I is a widespread phenomenon.
The paper employs solar observations of high spatial and spectral resolution to identify emission lines seen in the extended wings of Ca II H & K near the solar limb. Emission lines in the wings of H & K represent valuable diagnostics of the atmospheres of cool stars, with a varying information content which depends on their particular formation mechanism. In solar spectrograms different emission line formation mechanisms can be distinguished by the character of the spatial intensity variation (SIV) apparent in the lines. Various classes of H & K emission features, their spatial intensity variations and their formation mechanisms (of which some pose further problems) are discussed. A new extended list of line identifications is compiled based on their formation class and compared with other line lists. Evidence is found that stellar luminosity-sensitive lines tend to show large spatial intensity variation on the sun.
Sedimentary C32 hopanoic acid, one of the most abundant in nature and of probable bacterial origin, has been isolated for the first time as a single component and characterized by H-1 NMR. The 17 alpha H, 21 beta H configuration of the C31 alkane has been similarly confirmed.
The nova outburst is modeled by spherically accreting H-rich material onto a 1 solar mass He white dwarf at a rate of 10 to the -8th solar mass/yr. The star accretes for 5848 years, when the nuclear reactions run away near the base of the accreted envelope. The nuclear-energy generation rate rises to 4.6(8) solar luminosities, and the envelope expands in response to it. However, nova-like mass ejection does not occur because the envelope is of insufficient mass, the base of the envelope is only mildly electron degenerate, and there is no enrichment of the CNO abundance. To overcome these limiting conditions, it is suggested that the H-rich material be accreted either more slowly than 10 to the -10th solar mass/yr or with angular momentum. Outbursts resulting in the former case should be similar to the nova models computed by Starrfield, Truran, and Sparks. Outbursts in the latter case should be strengthened, and novae might result because the H-rich material will be mixed into the surface layers of the white dwarf, as first suggested by Kippenhahn and Thomas (1978).
Both Mg II h and k line fluxes are presented for a sample of 4 dMe and 3 dM stars obtained with the IUE satellite in the long wavelength, low dispersion mode. The observed fluxes are converted to stellar surface flux units and the importance of chromospheric non radiative heating in this sample of M dwarf stars is intercompared. In addition, the net chromospheric radiative losses due to the Ca II H and K lines in those stars in the sample for which calibrated Ca II H and K line data exist are compared. Active region filling factors which likely give rise to the observed optical and ultraviolet chromospheric emission are estimated. The implications of the results for homogeneous, single component stellar model chromospheres analyses are discussed.
Observations of the ultraviolet spectra of two locations in the H II region NGC 346 and of the entire H II region IC 1644 in the Small Magellanic Cloud (SMC) were made using the International Ultraviolet Explorer (IUE) satellite. The abundance of carbon in the nebulae was derived using theoretical model analysis combined with ground-based spectrophotometry of other emission lines. The abundance of C relative to H in the SMC was found to be lower by -0.9 dex compared with the Sun and lower by -0.8 dex compared with the Orion Nebula. This C deficiency is similar to that of O, Ne, S, and Ar in the SMC, but not as great as found for N. The sites and history of C nucleosynthesis in galaxies is similar to that of O, Ne, S, and Ar, in contrast to that of N, which appears to be more complex, perhaps because of a mixture of secondary primary sources or a significant contribution from intermediate-mass long-lived stars.
The controversial problem of H(-) radiative cooling in the solar chromosphere is examined. It is found, in agreement with Praderie and Thomas (1972, 1976), that H(-) is a substantial source of radiative heating in the outer atmosphere, especially when departures from LTE are important. The role of H(-) as a chromospheric heating agent must be considered carefully before net radiative cooling rates can be assessed from empirical chromospheric models, or calculations of nonradiative heating, for example by acoustic waves, can be pursued meaningfully.
A search has been made for H I shells in the 21-cm maps made by Heiles and Habing (1974) for absolute values of galactic latitude greater than 10 deg. A filter in the velocity dimension was used to enhance shell features over background gas. Positions, expansion velocities, column densities, and angular extents were measured for the 50 shells that were discovered. Incorporating distance estimates, masses and kinetic energies were estimated for the shells. A striking result was the failure of swept-up matter in a standard model for gas in the disk (density at the midplane approximately 1/cu cm; exponential scale height approximately 130 pc) to reproduce the observed shell column densities. While measured shell densities may be insufficiently corrected for background gas, the magnitude of this effect is too large to be explained by such a discrepancy alone. This may suggest that the shells seen in this survey occur in regions of relatively high density. The distribution of H I shells was compared with the distribution of other large-scale features in the Galaxy: H I shell structures are found to correlate with the positions of radio continuum loops I, II, and III, and to show little relation to the distribution of O and B stars.
The considered investigation shows that existing models of the formation of the H-alpha line during flares appear to provide clear qualitative evidence that heating of the H-alpha forming regions of the flare chromosphere in the bright H-alpha kernels observed during the impulsive phase of solar flares is not due primarily to heating by Coulomb collisions of a power-law distribution of 10-100 keV electrons with chromospheric material. It appears rather that some shorter-range process, involving possibly conduction or optically thick radiative transfer, is favored. Such a conclusion is clearly relevant to collisionless confinement modelling. However, much work remains to be done before there will be a basis for quantitatively testing the consistency of the considered picture with chromospheric diagnostics.
Results are given of observations of the UV spectra of several H II regions in the Magellanic Clouds, with emphasis on obtaining the carbon abundance from the UV lines of C II, C III, and C IV. The observations and results are described, and theoretical model calculations are presented of the H II regions and the relative abundances of H, He, C, N, O, S, Cl, and Ar computed from the UV and visual spectra. In addition, the abundance results for the Magellanic Clouds are compared with the sun, the Orion Nebula, and galactic planetary nebulae. In comparison with solar abundances, carbon is found to be depleted relative to hydrogen in the Magellanic Clouds by an amount larger than that of nitrogen and oxygen in the SMC and by an amount between that of nitrogen and oxygen in the LMC. It is noted that the results are consistent with a scenario that nitrogen and oxygen have greater primary yields in massive stars than carbon, which may be produced predominantly in less massive stars (such that C/N and C/O in galaxies are initially very low and subsequently increase with evolution). Subsequently, the C/N ratio may decrease as secondary production of nitrogen in less massive stars becomes significant.