220 research outputs found
Interstellar helium in interplanetary space
The velocity distribution function of He(+) in the solar wind at 1 AU is calculated with the assumption that the source is photoionization of a cold (T = 100 K), neutral interstellar wind. If the spiral magnetic field is noise free, the velocity distribution is diffuse and would not produce a peak at 4(E over Q) sub H in an E over Q particle spectrum. If the velocity of the interstellar wind with respect to the sun lies in the ecliptic, a large variation of the He(+) number density with respect to ecliptic longitude is expected
The Io sulfur torus in 1981
A Fabry-Perot spectrometer was used to obtain images of the Io torus in emission lines of S II (wavelength 6716 and 6731) and S III (wavelength 9531) in February and March 1981, on the 2.1 meter telescope at KPNO. The S II and S III images showed a large variation in brightness and radial extent. There is an indication the S II and S III emissions in the warm torus are correlated. The S II and S III emissions in the warm torus also have similar scale heights along the magnetic field lines of approximately 0.6 to 0.72 R sub J. The east-west asymmetry in the S II images taken at similar magnetic longitudes, but 2.5 Jovian rotations apart, supports the theory of convective motions suggested by others. In addition to the images, simultaneous measurements of the S II (6731 wavelength) line profile were also made on one night using a Fabry-Perot scanning spectrometer on the 4 meter at KPNO. The S II spectral scans implied ion temperatures of 52 (+ or - 10) x 10 to the 3rd at 5.2 to 5.6 R sub J from Jupiter and a minimum temperature of at least 3 x 10 to the 5th K at 6 R sub J from Jupiter
Fabry-Perot observations of comet Kohoutek
Observations of H alpha, H20(+), and emission lines from comet Kohoutek were made. Analyses of H alpha line profiles and line intensities indicate that the mean outflow velocity of the hydrogen atoms was 7.8 + or - 0.2 km s(-1) and that the hydrogen atom production rate varied for comet-sun distances between 1 AU and 0.4 AU. The identification of an H20(+) emission feature in certain H alpha scans indicates that the H20(+) ions were moving in a tailward direction with a velocity of 20 to 40 km s(-1) with respect to the comet nucleus. An upper limit of 1 part in 100 was found for the D/H ratio in the cometary atomic hydrogen cloud
Low intensity H-beta emission from the interstellar medium
A search for diffuse galactic H beta emission not associated with any known H II regions was conducted using a 2-inch-diamenter pressure-scanned Fabry-Perot spectrometer at the Coude focus of a 36-inch telescope. Observations were made near the directions of four pulsars. Emissions with intensities from 40,000 to 400,000 photons/sq cm sec ster (corresponding to emission measures of approximately 10 - 100) were detected in three of the directions. The data indicate an average ionization rate (assuming steady state) of approximately 10 to the minus 14th power/H-atom sec for the interstellar hydrogen in these directions and temperatures between 1000 and 10,000 K for the emitting regions. Plans were made to continue the investigation of these very faint hydrogen emission sources using a 6-inch-diameter Fabry-Perot spectrometer
Experimental evaluation of three leak detection and location concepts for space stations
Three leak (or precursor damage modes) detection and location concepts for space station overboard leakage were evaluated experimentally. The techniques are: (1) static and dynamic seal leak detector sensing of moisture or all gases in space cabin atmosphere, (2) active ultrasonic Lamb-wave detection of flaws or cracks in cabin wall, and (3) impact gage detection of stress waves induced in cabin pressure wall by meteoroid or orbital impact. The experimental results obtained in the program demonstrated that all three leak detection and location concepts are feasible. With further development, the methods can be integrated into an effective damage control system for advanced manned earth-orbital systems
Relation between composition and vacant oxygen sites in the mixed ionicelectronic conductors La5.4W1 yMyO12 delta M Mo, Re; 0 lt; y lt; 0.2 and their mother compound La6 xWO12 delta 0.4 lt; x lt; 0.8
A detailed analysis of specimen composition, water uptake and their interrelationship in the systems La6 xWO12 amp; 948; 0.4 amp; 8804; x amp; 8804;0.8 and La6 xW1 yMyO12 amp; 948; 0 amp; 8804;y amp; 8804;0.2; M Mo, Re is presented. The three specimen series were investigated in dry and wet D2O conditions. A systematic trend in mass loss and onset temperature variation was observed in La6 xWO12 amp; 948; 0.4 amp; 8804;x amp; 8804;0.8 . Even very small amounts lt; 1 wt of secondary phases were found to notably modify the specimen s water uptake and onset temperature of mass loss. The theoretical model for vacancy concentration available was used to calculate the vacant oxygen sites starting from mass loss values determined by thermogravimetry. A discrepancy between the calculated and observed concentration of vacant oxygen sites is observed for all three systems. The effect of substitution of W by Re or Mo on the vacancy amount is explained taking into account diffraction measurements and information on the oxidation state of the substituting elements Mo and R
A study of the interacting binary V 393 Scorpii
We present high resolution J-band spectroscopy of V 393 Sco obtained with the
CRIRES at the ESO Paranal Observatory along with a discussion of archival IUE
spectra and published broad band magnitudes. The best fit to the spectral
energy distribution outside eclipse gives = 19000 500 for the
gainer, = 7250 300 for the donor, = 0.13 0.02
mag. and a distance of = 523 60 pc, although circumstellar material
was not considered in the fit. We argue that V 393 Sco is not a member of the
open cluster M7. The shape of the He I 1083 nm line shows orbital modulations
that can be interpreted in terms of an optically thick pseudo-photosphere
mimicking a hot B-type star and relatively large equatorial mass loss through
the Lagrangian L3 point during long cycle minimum. IUE spectra show several
(usually asymmetric) absorption lines from highly ionized metals and a narrow
L emission core on a broad absorption profile. The overall behavior of
these lines suggests the existence of a wind at intermediate latitudes. From
the analysis of the radial velocities we find = 0.24 0.02
and a mass function of = 4.76 0.24 M. Our observations favor
equatorial mass loss rather than high latitude outflows as the cause for the
long variability.Comment: 13 pages, 14 figures, 7 tables. Accepted for publication in MNRAS,
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