Surface-gravity determinations for main- sequence B stars.
Main sequence B stars surface gravity determinations from comparison between model atmosphere computed and observed H gamma line equivalent widths
Peterson, D. M.↗
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Infrared absorptance of carbon monoxide at low temperatures.
IR absorptance of CO below room temperature, determining strength and half widths of lines in R branch of fundamental band
Hoover, G. M.↗
Studies of methane absorption in the Jovian atmosphere. I.
Methane rotational temperature in Jovian atmosphere deduced from equivalent widths of lines at 1.1 micron band
Fox, K.↗
High dispersion observations of Venus during 1972. The CO2 band at 7820 angstrom
Photographic plates of Venus which show the spectrum of the carbon dioxide band at 7820A were obtained at Table Mountain Observatory in September-October 1972. These spectra showed a semi-regular 4-day variation in the CO2 abundance over the disk of the planet. Evidence for temporal variations in the rotational temperature of this band and temperature variations over the disk was found. The two quantities, CO2 abundance and temperature, do not show any obvious relationship; however, an increase in the temperature usually is accompanied by a decrease in the abundance of CO2. The average temperature, found from a curve of growth analysis assuming a constant CO2 line of width, is 249 plus or minus 1.4 K (one standard deviation).
Young, L. D. G.↗
High-dispersion spectroscopic observations of Venus during 1968 and 1969. II - The carbon-dioxide band at 8689 A
Results are reported for an extensive series of high-resolution spectroscopic observations of the CO2 band at 8689 A in the atmosphere of Venus which were made over a period of one year at a dispersion of 2 A/mm for Venus phase angles varying from 10 to 126 deg. The equivalent widths of lines in the band are measured, the rotational temperature is calculated, and the CO2 abundance over various areas on the planet is determined. The results are compared with those of previous observations of the CO2 bands at 8689, 7820, and 7883 A, and good agreement is found regarding the temperatures and abundances derived for the different bands. It is concluded that the CO2 abundance varies over the planet and that its distribution does not remain constant with time.
Schorn, R. A. J.↗
Observations of Lorentzian lines with slits of finite widths
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Sulzmann, K. G. P.↗
An analysis of Saturn's methane 3 nu /3/ band profiles in terms of an inhomogeneous atmosphere
Observed profiles of the R branch of Saturn's CH4 3 nu (3) band are compared with synthetic profiles computed from inhomogeneous models which are consistent with Saturn's H2 quadrupole-line equivalent widths. A C/H ratio approximately three times the solar value and a CH4 abundance of about 100 m am are found. Scattering plays a significant role in the formation of manifold profiles below a depth where the H2 abundance is 20-30 km am.
Macy, W., Jr.↗
Interpretation of high-resolution spectra of Mars. IV - New calculations of the CO abundance
Recent measurements of the half-widths of lines, pressure broadened by CO2 at a temperature of 200 K, in the 0-2 band of CO are used to reestimate the amount of CO in the atmosphere of Mars. Assuming an air-mass factor of 3.5, the amount of CO in a vertical path through the Martian atmosphere is estimated to be approximately 5.6 cm-atm. A comparison of CO and O2 abundances indicates that there is about 3.4 times as much molecular oxygen on Mars than expected. It is suggested that the extra oxygen may come from photodissociation of water.
Young, L. D. G.↗
X-ray spectra of Hercules X-1. I - Iron line fluorescence from a subrelativistic shell
The X-ray spectrum of Her X-1 was observed in the energy range from 2 to 24 keV from August 29 to September 3, 1975. Emission features are observed near the K-alpha iron-line energy which exhibit both broadening and a double line structure. The total luminosity in these features is about 4 by 10 to the 35th power ergs/s. Iron line fluorescence from an opaque cool (not exceeding 1 million K) shell of material at the Alfven surface provides the necessary luminosity in this feature. The double line structure and the line energy width can be due to Doppler shifts if the shell is forced to corotate with the pulsar at a radius of at least 800 million cm. Implications of this model regarding physical conditions near Her X-1 are discussed.
Pravdo, S. H.↗
Detection of the 12.28 micron rotational line of molecular hydrogen in the Orion molecular cloud
The pure rotational S(2) transition of molecular hydrogen at 12.28 microns has been detected in emission from the region of vibrational-rotational line emission in Orion. The line was resolved both spectrally and spatially, and the line shapes, widths, and velocities are consistent with those observed in the upsilon = 1-0 transitions. The results put new constraints on the structure, temperature, and dynamics of the region of molecular hydrogen emission.
Beck, S. C.↗
The discovery of an 81 minute modulation of the X-ray flux from 2A0311-227
The X-ray flux from 2A0311-227 was modulated at the 81 min orbital period of its optical counterpart. An absorption dip with N sub H equivalent to 5 x 10 to the 22nd power H atoms per square cm was observed at magnetic phase 0.42. It was interpreted as the accretion column of a magnetic white dwarf passing in front of the X-ray source. The spectrum was thermal with a temperature of 18 keV and a 300 eV equivalent width iron line at 6.6 keV.
White, N. E.↗
The 805s X-ray pulsar H2252-035
The X-ray flux from the 3.6 hr binary system H2252-035 is shown to be modulated at a period of 805s. The spectrum is consistent with either a 1.4 photon index power law or 20 keV thermal model. A 560t0r-350 eV equivalent width iron line is seen at approximately 6.7 keV. The possibility that this system contains a slowly rotating neutron star is discussed.
White, N. E.↗
An 81 minute modulation of the X-ray flux from 2A 0311-227
It is demonstrated that the X-ray flux from 2A 0311-227 is modulated at the 81 minute orbital period of its optical counterpart. An absorption dip with N sub H approximately equal to 5 x 10 to the 22nd H atoms per sq cm is observed at magnetic phase 0.42 that is interpreted as the accretion column of a magnetic white dwarf passing in front of the X-ray source. The spectrum is thermal with a temperature of 18 keV and a 300 eV equivalent-width iron line at 6.6 keV.
White, N. E.↗
Two-photon excitation of nitric oxide fluorescence as a temperature indicator in unsteady gasdynamic processes
A laser-induced fluorescence technique based on the pulsed two-photon excitation of NO is presented which is especially suited for the measurement of fluctuating temperatures in cold turbulent flows. The technique uses the fluorescence from the UV gamma bands of NO produced by two-photon excitation of NO (A 2 Sigma +, nu-prime = 0 - X 2 Pi, nu-double prime = 0) to obtain a rotational temperature. An analysis is presented of relevant aspects of the two-photon absorption process including microphysical processes, spectral intensities as a function of transition and laser spectral widths, line-shape integrals, the nonequilibrium response of the medium to a laser pulse, fluorescence energies, signal to noise ratio, and focusing effects. An analysis of absolute two-photon absorptivity measured in a nonflowing cell is then presented and used to predict signal to noise ratios greater than 50 for supersonic flows at temperatures below 300 K.
Mckenzie, R. L.↗
The 805 second X-ray pulsar H2252-035
It is shown that the X-ray flux from the 3.6 hr binary system H2252-035 is modulated at a period of 805 sec, and that its spectrum is consistent with either (1) a 1.4 photon index power law, or (2) a greater-than-20-keV thermal model. A 560 + or - 350 eV equivalent-width iron line at about 6.7 keV is noted, and the possibility that the H2252-035 system contains a slowly rotating neutron star is discussed.
White, N. E.↗
Evolution of chromospheres and coronae in solar mass stars - A far-ultraviolet and soft X-ray comparison of Arcturus /K2 III/ and Alpha Centauri A /G2 V/
IUE far-UV and Einstein Observatory soft X-ray observations for the red giant Arcturus and the nearby yellow dwarf Alpha-Centauri A, which are archetypes of solar mass stars in different stages of evolution, are compared. Evidence is found for neither coronal soft X-ray emission from the red giant, at surface flux levels of only 0.0006 that detected previously for the yellow dwarf, nor C II and IV resonance line emission at surface flux levels of only 0.02 those of the yellow dwarf. The resonance line upper limits and previous detections of the C II intersystem UV multiplet 0.01 near 2325 A provide evidence for an Arcturus outer atmosphere that is geometrically extended, tenuous and cool. The red giant has, in addition, a prominent cool stellar wind. An extensive tabulation of line identifications, widths and fluxes for the IUE far-UV echelle spectra of the two stars is given, and two competing explanations for the Wilson-Bappu effect are discussed.
Ayres, T. R.↗
IUE observations of accretion columns in two Zeta Aurigae-type systems
The existence of an accretion column in 32 Cyg is reported, and the presence of the accretion column in Zeta Aurigae is confirmed. Secular variations have been detected for Zeta Aur. Refinements are suggested for the model of Ahmad, Chapman, and Kondo (1983). Resonance line equivalent widths have been calculated and the implications for flow geometry, secular variability, and plasma density are discussed.
Ahmad, I. A.↗
High resolution infrared absorption spectra of various trace gases present in the upper atmosphere of the Earth
The objective of NASA Grant NsG 7473 was to obtain and analyze high resolution infrared absorption spectra of various trace gases present in the Earth's upper atmosphere. The goal of the spectral analysis was to obtain values of absorption line strengths, widths and frequencies of sufficient accuracy for use in upper atmosphere trace gas monitoring. During the early phase of the grant, high resolution spectra were obtained from two instruments. One was the 0.02/cm resolution vacuum grating spectrometer at the Florida State University and the other was the 0.01/cm resolution Fourier transform spectrometer at the McMath solar telescope at the Kitt Peak Observatory. Using these instruments, a considerable amount of spectra of methane and hydrogen peroxide were obtained and analyzed. During the latter years of the project, data taking was halted while efforts were devoted to building a new 0.0025/cm resolution vacuum Fourier transform spectrometer. Progress during this phase of the grant then became greatly slowed due to a lack of suitable graduate students in the program. However, the instrument was completed and brought to the point of producing interferograms.
Hunt, Robert H.↗