Showing papers in "Astrophysical Journal Supplement Series in 1978"
TL;DR: In this paper, a steady-state solution for the temperature of diffuse gas (including radiative cooling and recombination, cosmic ray or X-ray heating and ionization, grain photoelectric heating, and other heating mechanisms) is found.
Abstract: Photoelectric emission from interstellar grains is reexamined, and it is argued that some of the assumptions made by other authors lead to an overestimate of the heating rate associated with this process, particularly at temperatures T> or approx. =3000 K. Steady-state solutions for the temperature of diffuse gas (including radiative cooling and recombination, cosmic ray or X-ray heating and ionization, grain photoelectric heating, and other heating mechanisms) are found. Grains do not contribute significantly to the heating of the ''hot'' (Tapprox. =8000 K) phase, although they dominate the heating of the ''cold'' (Tapprox. =100 K) phase. The minimum pressure for which the ''cold'' phase can exist is sensitive to the choice of grain properties and grain abundance, and under some circumstances the coexistence of two distinct phases in pressure equilibrium is forbidden. A steady-state model with intercloud H I heated by soft X-rays and clouds heated by grain photoemission is in accord with some observations but lacks intermediate-temperature H I. The time-dependent cooling of a fossil H II region is calculated; grain photoelectric heating significantly prolongs the time required for the gas to cool. Fossil H II in the wakes of runaway O stars may produce significant amounts of themore » intermediate temperatue (500> or approx. =T> or approx. =3000 K) H I inferred from 21 cm observations.« less
1,348 citations
TL;DR: In this paper, the fundamental properties of the most luminous known stars in our Galaxy are determined for future comparison with results for the most lumens in other galaxies, and a catalog of over 1000 supergiants and O stars in associations and clusters is included.
Abstract: In this paper the fundamental properties of the brightest known stars in our Galaxy are determined for future comparison with results for the most luminous stars in other galaxies. The H-R diagrams (M/sub v/ versus spectral type and M/sub bol/ versus log T/sub e/), the luminosities of the brightest stars, and the ratios of blue to red supergiants are all discussed, and a catalog of over 1000 supergiants and O stars in associations and clusters is included at the end of the paper.The ''theoretical'' H-R diagram (M/sub bol/ versus log T/sub e/) reveals a group of superluminous O stars with M/sub bol/ between -12 mag, a lack of evolved supergiants at these very high luminosities, and an apparent upper limit to the luminosities of the later-type supergiants (>B5) near M/sub bol/=-9.5 mag.The most luminous red supergiants have a maximum visual luminosity near M/sub v/approx. =-8 mag, supporting the suggestion by Sandage and Tammann that they are good distance indicators. Excluding the superluminous star Cyg OB 2 No. 12 (M/sub v/approx. =-9.9 mag), the brightest blue stars are found at M/sub v/approx. =-8.5 mag.The variation of the ratio of blue to red supergiants with luminosity is discussed. There is also evidencemore » for a gradient in this ratio with distance from the galactic center, although the results are limited by the incompleteness of the data.« less
705 citations
TL;DR: In this paper, a roughly linear correlation is found between these two quantities for visual extinctions in the range from about 1.5 to 5 mag and it is argued that this correlation can be extended up to about 10 mag and that the standard gas-to-extinction ratio can be expected to remain valid in the sources studied.
Abstract: LTE (C-13)O column densities are compared with the corresponding values of beam-convolved visual extinction at more than 100 locations within 38 different interstellar dark clouds. A roughly linear correlation is found to exist between these two quantities for visual extinctions in the range from about 1.5 to 5 mag. It is argued that this correlation can be extended up to about 10 mag and that the standard gas-to-extinction ratio can be expected to remain valid in the sources studied. The correlation of LTE (C-13)O column density with visual extinction is used to obtain an equation for the H2 column density associated with a given (C-13)O column density. It is shown that if the clouds studied are assumed to be chemically homogeneous, the equation obtained implies that at least 12% of all gas-phase carbon is in the form of CO. Comparison of the observational data with various theories proposed for molecule formation in dark clouds indicates that Langer's (1977) ion-molecule scheme accounts well for the observations when the fractionation channel of Watson et al. (1976) is included.
439 citations
TL;DR: In this paper, positions and intensities for the Uhuru (SAS A) X-ray satellite observatory are presented for 339 sources observed by the AUX-1 and AUX2A satellite observatories, including binary stellar systems, supernova remnants, Seyfert galaxies, clusters of galaxies, and new class of superclusters of galaxies.
Abstract: Positions and intensities are presented for 339 X-ray sources observed by the Uhuru (SAS A) X-ray satellite observatory. We find good agreement between the sources in this catalog and those in the 3U and 2A catalogs. Optical and radio counterparts are suggested based on positional coincidence. The major classes of identified objects include binary stellar systems, supernova remnants, Seyfert galaxies, clusters of galaxies, and posibly the new class of superclusters of galaxies.
423 citations
TL;DR: The spectral identifications and absolute intensities of lines in the EUV spectrum for various solar features, such as the quiet sun, active regions, coronal holes, and the off-limb corona, are presented and discussed in this paper.
Abstract: The spectral identifications and absolute intensities of lines in the EUV spectrum for various solar features, such as the quiet sun, active regions, coronal holes, and the off-limb corona, are presented and discussed. Composite spectra have been assembled and processed from the ATM ultraviolet spectrometer data with a spectral resolution of 1.6 A over the range 280-1350 A. These spectra represent a self-consistent set of observations with good photometric calibration, in which intercomparison of intensities from different regions is used to assist in line identifications and to draw general conclusions on average physical conditions in the solar atmosphere. The quiet-sun line intensities obtained near solar minimum are compared with OSO 6 results near solar maximum to provide an estimate for the changes over the solar cycle.
300 citations
TL;DR: The nucleosynthetic origin of the rare proton-rich isotopes, usually called ''p-process'' isotopes is examined in this article, where a particularly interesting context for this synthesis is found to be explosive events characterized by peak temperatures in the range 2.0 to 3.0 x 10/sup 9/K. At these temperatures a series of photodisintegration reactions operating upon a distribution of r- and s-process seeds produces an abundance pattern that displays striking similarities to that of the p-process nuclei in the solar system.
Abstract: The nucleosynthetic origin of the rare proton-rich isotopes, usually called ''p-process'' isotopes, is examined. A particularly interesting context for this synthesis is found to be explosive events characterized by peak temperatures in the range 2.0 to 3.0 x 10/sup 9/ K. At these temperatures a series of photodisintegration reactions operating upon a distribution of r- and s-process seeds produces an abundance pattern that displays striking similarities to that of the p-process nuclei in the solar system. The large proton densities usually required for such synthesis are not needed. Requisite conditions for this model are expected to occur naturally in those zones of supernovae that have experienced helium and perhaps carbon burning prior to explosion. Implications for supernova structure, presupernova evolution, and cosmochronology are discussed and a critical discussion of other current p-process models is presented.
271 citations
TL;DR: A set of 46 evolutionary sequences has been computed for stars ascending the red giant branch for the first time, extending from the subgiant branch to the onset of helium burning within the core, cover the following ranges in the helium abundance Y, the heavy-element abundance Z, and the mass M: 0.20 M/sub sun as discussed by the authors.
Abstract: A set of 46 evolutionary sequences has been computed for stars ascending the red giant branch for the first time. These red giant sequences, extending from the subgiant branch to the onset of helium burning within the core, cover the following ranges in the helium abundance Y, the heavy-element abundance Z, and the mass M:0.10< or =Y< or =0.40, 0.00001< or =Z< or =0.04, and 0.70< or =M< or =2.20 M/sub sun/. Combinations of these values appropriate to galactic and globular clusters have been emphasized. The effects of varying the rate of neutrino emission from zero to twice the normally adopted value have also been investigated. Except for one sequence, helium ignition occurred under degenerate conditions. Extensive tabulations of the numerical results are provided, and from these data the systematic dependences of red giant properties on composition and mass can be determined. For (M,Y,Z) = (0.80,0.30,0.001), the core mass M/sub c/ at the flash and its derivatives are given by M/sub c/=0.474 M/sub sun/, partialM/sub c//partialY=-0.24, partialM/sub c//partial logZ=-0.007, and partialM/sub c//partialM=-0.038. These derivatives depend significantly on the composition and mass. When neutrino emission is neglected, M/sub c/ decreases by 0.03 M/sub sun/. The enhanced rates of neutrino emission duemore » to neutral current interactions increase by M/sub c/ by about 0.007 M/sub sun/. The temperature inversion produced by the neutrino cooling of the core leads to a noncentral flash in almost all of the sequences. The flash site shifts outward in mass with decreases in Y of M or increases in the rate of neutrino emission. For many of the sequences a temporary period of decreasing surface luminosity occurs during the early part of the red giant phase. This luminosity drop is more prominent at low values of Y and large values of Z. The morphology of the red giant tracks in the H-R diagram is discussed.« less
182 citations
TL;DR: In this paper, the rates for excitation of CO, CS, OCS, and HC3N by collisions with He atoms and H2 molecules are presented from extensive theoretical calculations using methods of known reliability.
Abstract: Rates for excitation of CO, CS, OCS, and HC3N by collisions with He atoms and H2 molecules are presented. These have been obtained from extensive theoretical calculations using methods of known reliability. In general, rates necessary for modeling interstellar molecular clouds with kinetic temperatures to 100 K have been included. Methods for fitting these rates in more compact form are discussed.
177 citations
132 citations
TL;DR: In this paper, the four principal subgroups of the Orion Nebula association were examined in detail using individual distances and reddening values determined for their B type members, and an eastward increase in distance was found for subgroup 1b but the reddening law for the east Belt appeared normal.
Abstract: The four principal subgroups of the association were examined in detail using individual distances and reddening values determined for their B type members. Subgroup 1a appeared not to show a spread in age nor did it show a systematic distance increase with right ascension when fainter members were considered. An eastwardly increase in distance was found for subgroup 1b but the reddening law for the east Belt appeared normal. Small subclusterings in the vicinity of the Orion Nebula appeared not to differ in the evolutionary state but their ages were considerably greater than those of stars in the nebulae and its associated cluster.
119 citations
TL;DR: In this article, the authors observed the interstellar medium in the directions of 27 extragalactic sources at high and intermediate galactic latitudes at 21 cm wavelength with the upgraded Arecibo telescope (HPBW=3'.2, gainapprox.6 K Jy/sup -1/).
Abstract: We have observed the interstellar medium in the directions of 27 extragalactic sources at high and intermediate galactic latitudes (vertical-barb/sup ii/vertical-bar>5/sup 0/) at 21 cm wavelength with the upgraded Arecibo telescope (HPBW=3'.2, gainapprox.6 K Jy/sup -1/). The small beam greatly reduces the uncertainty in the derived on-source emission profile and increases confidence that it corresponds to the same material as the absorption spectrum. Each region has been observed for approximately 2 hours to tetect optical depths as low as 10/sup -2/ in most cases. The data allow the derivation of optical depths, harmonic mean spin temperatures, and column densities for the neutral hydrogen as a function of velocity in the range -200
TL;DR: In this article, the steady state abundances for a system of chemical reactions relevant to interstellar clouds are presented for densities of 10 cm/sup -3/ to 10/sup 6/cm/sup −3/ with various values for the cosmic element abundances.
Abstract: Steady-state abundances are presented for a system of chemical reactions relevant to interstellar clouds. A number of reactions with recently measured rates are included. The system is solved for densities of 10 cm/sup -3/ to 10/sup 6/ cm/sup -3/ with various values for the cosmic element abundances. Of the 100 species in the scheme, approximately 20 have been observed. The chemistry of the observed species is discussed and the calculated abundances are compared with observed abundances.
TL;DR: In this article, the influence of envelope density, temperature, and inclination on the Balmer line profiles, the line polarization, the continuum energy distribution, and the continuum polarization was analyzed for a large number of Be star models.
Abstract: We present the results for a large number of Be star models, detailing the influence of envelope density, temperature, and inclination on the Balmer line profiles, the line polarization, the continuum energy distribution, and the continuum polarization. We show that inclination effects are substantial, both in the emission lines and in the continuum. Changes in the envelope density and temperature also have a dramatic effect on the lines and the continuum. It is shown that any small set of observable features does not specify a unique model. We suggest a variety of observable features which appear to be most sensitive to model parameters.
TL;DR: In this paper, high-dispersion spectrograms were used to derive the distribution of rotational velocities for a sample of 256 late B-type stars, and a statistical treatment of the data showed that the distribution reached a maximum in the velocity interval 300.1.
Abstract: High-dispersion spectrograms are used to derive the distribution of rotational velocities for a sample of 256 late B-type stars. Approximately half the stars have sharp lines (upsilon sini<100 km s/sup -1/), and a statistical treatment of the data shows that the distribution of true rotational velocities psi (upsilon) reaches a maximum in the velocity interval 300.1 is marginally higher among the HgMn stars (31%) than among normal B-type stars (19%) in the same temperature range, probably because slow rotation, which is characteristic of such binaries, favors the appearance of HgMn anomalies. However, the majority of HgMn stars are single, and their slow rotation cannot be attributed to tidal interactions. The HgMn stars are single, and their slow rotation cannot be attributed to tidal interactions. The HgMn stars are found throughout the main-sequence band from the zero- to the terminal age main sequence. The present observations show that HgMn stars are not distinguished from normal ones by their age, duplicity, rotation, or any combination of these characteristics.
TL;DR: In this paper, a program of mapping several molecular transitions in these clouds has been undertaken, and the results of observations of the J=1..-->..0 rotational transitions of CO, /sup 13/CO, C/sup 18/O, and CS, the J, K=1, 1 and J, k=2, 2 inversion transitions of NH/sub 3/, the J/sub KKprime/=1/sub 11/..-->, 1/sub 10/ and J/ sub KK prime/=2/sub 12/..
Abstract: In order to better understand galactic dust globules, a program of mapping several molecular transitions in these clouds has been undertaken. The results of observations of the J=1..-->..0 rotational transitions of CO, /sup 13/CO, C/sup 18/O, and CS, the J=2..-->..1rotational transitions of CS and C/sup 34/S, the J, K=1, 1 and J, K=2, 2 inversion transitions of NH/sub 3/, the J/sub KKprime/=1/sub 11/..-->..1/sub 10/ and J/sub KKprime/=2/sub 12/..-->..2/sub 11/ transitions of H/sub 2/CO, and the OH /sup 2/Pi/sub 3/2/F=2..-->..2 and F=1..-->..1 transitions are reported here. Twelve globules have been selected for observation; seven of these were studied in detail and the remainder observed only sparsely. A strong positive correlation appears to exist between the spatial extent of the molecular emission (or absorption) and the optical features of the globule. Even the main isotope of CO shows this correlation between dust extinction and molecular emission. Close examination of the Palomar prints reveals dust wherever CO is observed, and CO is probably a good tracer of dust extinction.The simultaneous observation of many molecular transitions has proven useful in obtaining reliable physical parameters for the dust globules. The kinetic temperatures of the globules are almost always approx.10 K, and the derived H/sub 2/more » densities are 10/sup 3.4/-10/sup 4.5/ cm/sup -3/. The density in the core of the globules could well be larger than these value, which represent an average for the entire cloud. The kinetic temperature appears uniform across each cloud (within a few kelvins), in agreement with theoretical predictions. All of the globules studied in detail appear to be gravitationally bound and collapsing objects. Rotation has been observed in at least two globules (B163 and B163 SW). The projected axis of rotation is in a direction opposite to that of the Galaxy, with the globules apparently rotating antiparallel to the galactic plane.« less
TL;DR: In this article, the distribution of redshift among the QSOs in the various samples are not significantly different and a number of correlations are found among the observed properties of the sample members, such as the correlation between redshift and apparent magnitude, and the data are shown to be in good agreement with a simple Hubble (inverse square) law, without luminosity evolution.
Abstract: New spectroscopic observations of nearly 100 QSOs are reported, and are combined with earlier data to compile observationally complete samples of QSOs selected from the 4C (178 MHz) and Parkes (2700 MHz) radio source surveys. The largest samples from these surveys contain 76 and 60 objects, respectively. Possible observational selection effects are considered and the samples are shown to be almost free of them. The distributions of redshift among the QSOs in the various samples are not significantly different. A number of correlations are found among the observed properties of the sample members. One, already known, is that between redshift and apparent magnitude, and the data are shown to be in good agreement with a simple Hubble (inverse-square) law, without luminosity evolution. Another is between apparent magnitude and radio spectral index. It results from the brighter absolute magnitudes of the objects whose radio spectra are flatter than ..nu../sup -0.5/, which corresponds to the division between sources with small radio components and those with extended radio structure.Adopting the hypothesis that the QSO redshifts are cosmological, the earlier evidence for strong evolution in the QSO properties is amply confirmed. The V/V/sub m/ test gives a mean value of 0.683 +- 0.024 rmsmore » for q/sub 0/=1, compared with the value (0.5) that is appropriate for a uniform distribution of objects in comoving space. However, if the reshifts are not cosmological in origin, and the QSOs are nearby, the V/V/sub m/ test indicates that they are distributed uniformly in space. The values of V/V/sub m/ calculated using the cosmological hypothesis are shown to be insensitive to reasonable changes in parameters such as the optical and radio limits adopted for the samples, the deceleration parameter q/sub 0/, and the values of redshift for objects with apparently continuous spectra. There is, however, a dependence of V/V/sub m/ on radio spectral index.« less
TL;DR: In this article, a theory of radiating shock waves traveling into a partially preionized medium was proposed to explain the observations of HH objects with the 3.9 m AAT and the 1.9m Mount Stromlo telescopes.
Abstract: Extensive absolute spectrophotometry of HH objects has been obtained with the 3.9 m AAT and the 1.9 m Mount Stromlo telescopes. Systematic trends in their spectral characteristics have been found. All the observations can be explained in a quantitative manner using a theory of radiating shock waves traveling into a partially preionized medium.There are probably two classes of stellar objects driving the shocks. These are either B-type protostars in the process of breaking up optically thick dust cocoons, or FU Orionis-type stars losing mass. In either case, high luminosities and/or high mass-loss rates are required. If the stellar object is an FU Orionis object, these must be maintained over time scales of order 100 years.
TL;DR: In this article, the spectral-flux distributions of variable extragalactic sources have been observed over the wavelength range 0.36 µm to 3.5 µm in terms of injection and energy loss of high-energy electrons radiating synchrotron radiation.
Abstract: The characteristics of the changes in the shapes of the spectral-flux distributions of variable extragalactic sources have been observed over the wavelength range 0.36..mu..m to 3.5..mu..m. Pronounced activity has been observed in the sources AO 0235+164, 3C 120, PKS 0735+178, OJ 287 (0851+202), and B2 1308+326. The slope of the spectral-flux distribution has been observed to change significantly in some cases during transitions in observed flux. These changes are interpreted in terms of injection and energy loss of high-energy electrons radiating synchrotron radiation.
TL;DR: In this article, an attempt is made to account for the observational fact that the intensity ratios of the lower Balmer lines seen in emission from QSOs, type 1 Seyfert galaxies, and other related active galaxies are not what would be expected from the conventional picture of lines generated in a recombining hydrogen plasma.
Abstract: An attempt is made to account for the observational fact that the intensity ratios of the lower Balmer lines seen in emission from QSOs, type 1 Seyfert galaxies, and other related active galaxies are not what would be expected from the conventional picture of lines generated in a recombining hydrogen plasma. Previous observations of emission-line intensities in QSOs and Seyfert galaxies are reviewed. The various processes included in the rate coefficients of the calculations are then described, viz., free-free, bound-free, and bound-bound transitions, radiative transfer, and angular-momentum mixing. The strengths of the various emission lines are calculated by using more accurate values for the transition rates, including excitation and deexcitation simultaneously, and providing for finite rates in optically forbidden transitions. Numerical results are presented for the cases of ground-state collisional excitation, reabsorption of the upper Balmer lines, and collisional deexcitation. The results are applied to construct a model for the emission-line gas in a QSO and to discuss limits on models of Seyfert galaxies.
TL;DR: The relationship between the dynamics of the interstellar gas and the thermal and chemical effects associated with interstellar molecules and dust is investigated in this article, using the equations of hydrodynamics; only radial motions are considered, and the heat, chemical, and radiative transfer equations are solved simultaneously with the hydrodynamic equations.
Abstract: The relationship between the dynamics of the interstellar gas and the thermal and chemical effects associated with interstellar molecules and dust is investigated. The evolution of a rather massive isolated initially diffuse cloud under self-gravity is studied, using the equations of hydrodynamics; only radial motions are considered, and the heat, chemical, and radiative-transfer equations are solved simultaneously with the hydrodynamic equations. The relevant chemistry is described along with the thermal model, the radiative-transfer process, and the numerical methods employed. Results for a contracting cloud are discussed in terms of the problem of initial conditions, the dynamical evolution of the cloud, its chemical and thermal evolution, time scales, and column densities. It is shown that the chemical evolution of a massive contracting diffuse cloud is sensitive to such physical properties as temperature and ion abundances, that warm and cool versions of a typical cloud evolve differently, and that the physical origin of this effect is the level of heating due to H2 formation on interstellar dust grains.
TL;DR: In this article, photoelectric scans of HCap alpha in the spectra of 35 bright Be stars accessible from Flagstaff, Arizona, were obtained during five observing periods in 1975--1977 with the Perkins 72 inch (18 m) reflector.
Abstract: Photoelectric scans of Hcap alpha in the spectra of 35 bright Be stars accessible from Flagstaff, Arizona, were obtained during five observing periods in 1975--1977 with the Perkins 72 inch (18 m) reflector Variations in total emission and/or line profile were detected for most of the stars on time scales of months Evidence of variability from night to night and, in a few cases, during a night was also found, but the reality of such short-term changes is less certain
TL;DR: In this article, the rates of excitation of ortho-H2CO by collisions with He have been extended to higher rotational levels and kinetic temperatures to 80 K. Pressure-broadening widths for several spectral lines have been obtained from these calculations and are found to agree with recent data within the experimental uncertainty of 10%.
Abstract: Previous calculations for rates of excitation of ortho-H2CO by collisions with He have been extended to higher rotational levels and kinetic temperatures to 80 K. Rates for para-H2CO have also been computed. Pressure-broadening widths for several spectral lines have been obtained from these calculations and are found to agree with recent data within the experimental uncertainty of 10%. Excitation of formaldehyde by collisions with H2 molecules is also discussed.
TL;DR: In this article, photoelectric and photographic surveys of the local group dwarf galaxy IC 1613 have been conducted to establish its structure and content, and it has been shown that it is dominated by a thin disk with an angle of inclination to the sky of about 50/sup 0/ and a major-axis position angle of about 90/Sup 0/
Abstract: Local Group dwarf galaxy IC 1613 is subjected to photoelectric and photographic surveys in order to establish its structure and content. Isophotes illustrate its structure and are compared with galaxy-wide star counts. Analysis of isophotes suggests that IC 1613 may be dominated by a thin disk with an angle of inclination to the sky of about 50/sup 0/ and a major-axis position angle of about 90/sup 0/. Integrated magnitude is B/sub 0/=9.80 and the absolute magnitude is M/sub B,0/=-14.63. Luminosity profiles show an exponential decrease outward with a gradient of 1.19 mag per kpc. The bright-star density has a considerably steeper slope, indicating that the luminosity function changes with position in the sense that the proportion of bright stars (M/sub B/< or approx. =-3) decreases outward. The present data agree well with the luminosity function published by Sandage and Katem.The integrated color of IC 1613 and its color distribution are derived from the photoelectric measurements. The total color is B--V=+0.71 +- 0.05, and the color is blue in regions rich in bright stars and redder in outer areas, possibly due to the apparent old-star envelope population.Twenty OB associations are identified and are shown to be concentrated primarily in the coremore » and in the NE and NW quadrants of the galaxy. They are more narrowly distributed spatially than the general field stars with B< or approx. =-3, and in size, density, and content are very similar to those in NGC 6822, having a mean diameter of 164 pc. There is a tight correlation between size and population. A list of 43 possible star clusters is given, most of them similar in size and population to the Pleiades or M11. This is at least as many clusters as would be expected on the basis of extrapolation from the LMC. The dust content, judged from the lack of many dark nebulae and from background galaxy counts, is probably small. It is tentatively concluded that the relative dust content of irregular galaxies is a function of galaxy mass.« less
TL;DR: The positions of all known radio supernova remnants have been searched for optical emission nebulosity as mentioned in this paper, and a total of 29 SNRs have now been observed optically, including G74.8 + 0.6, G78.1 + 1.8, G284.9 + 2.4 and G339.2--0.4.
Abstract: The positions of all known radio supernova remnants have been searched for optical emission nebulosity. New optical supernova remnants identified during this program are G130.7 + 3.1= 3C 58, G206.9 + 2.3= PKS 0646 + 06, G296.1--0.7, G326.3--1.8= MSH 15--56, and G327.6 + 14.5= PKS 1459--41= Lupus SN 1006. New observations suggest that G74.8 + 0.6, G78.1 + 1.8, G284.2--1.8, and G339.2--0.4 are unlikely to be supernova remnants.Of 124 probable galactic SNRs listed in Table 1 all but one (G343.2--5.6) are known to be radio sources. A total of 29 SNRs have now been observed optically. In the anticenter direction (90/sup 0/
TL;DR: In this article, the column densities of CS dust from the observed height of the 10 ¼ m silicate feature were derived from the predicted energy distributions from model dust shells including the effects of self-absorption by dust.
Abstract: Optical and infrared observations are combined to study the circumstellar (CS) envelopes of late-type giants and supergiants. Coude spectrograms at 6.7 A mm/sup -1/ and echellograms at 5.1 A mm/sup -1/ were obtained to observe violet-displaced CS line cores. The solution of the equation of transfer in an expanding, extended atmosphere is used to derive the column density of CS matter from the observed line asymmetries. Infrared fluxes are presented from new infrared photometry, and infrared photometry and spectrophotometry from the literature. The predicted energy distributions from model dust shells including the effects of self-absorption by dust are used to derive the column densities of CS dust from the observed height of the 10 ..mu..m silicate feature.Comparison of the derived amounts of CS gas and dust reveals a large variation in the gas-to-dust ratio from star to star, with the metals in the stars of spectral type M6 and later appearing almost entirely as grains. The inner radii of the envelopes are not well determined; the observed shells probably lie outside an extended turbulent region above the photosphere. Particle densities at the inner shell radii range from 10/sup 7/ to 10/sup 8/ cm/sup -3/. Mass loss rates range from 10/supmore » -8/ to 10/sup -6/ Msun yr/sup -1/ and are shown to be relatively insensitive to the gas-to-dust ratio, indicating that the mechanism of mass loss may be something other than radiation pressure on dust grains.« less
TL;DR: In this paper, a wavelength list of spectral lines between 1000 and 1940 A is presented for the solar flare that occurred on June 15, 1973. The spectral resolution is 0.06 A. Intensities, identifications and estimates of line widths are given.
Abstract: A wavelength list of spectral lines between 1000 and 1940 A is presented for the solar flare that occurred on June 15, 1973. The spectra were recorded by the NRL spectrograph on Skylab. The spectral resolution is 0.06 A. Intensities, identifications, and estimates of line widths are given. The intensity of the continuum is also given at 50-A intervals between 1400 and 1900 A. The wavelength list includes about 1400 lines; about 30% of these lines are not indentified. Because of the high wavelength resolution, this line list will be useful as a source of identification for some stellar as well as solar spectra. In particular, the list should be a useful aid in the identification of lines in the spectra of stars with classifications close to that of the sun. Spectra of such stars may be obtained from the recently launched IUE spacecraft. It is also interesting to compare the list with some of the spectra of early-type stars recorded by Copernicus.