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Weiler, E. J.

Publications and source records attributed to Weiler, E. J..

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Abundance of interstellar aluminum

New observations of Al II 1670 A, the only line of the dominant ionization stage of interstellar aluminum detected to date, are presented. Observations of ionized silicon are used to define an empirical curve of growth from which aluminum depletions can be derived. The depletion ranges from a factor of 10 in alpha Vir, with E(B-V) of about 0.04, to a factor of 1000 in omicron Per. The depletion is similar to that of iron, but a factor of 2-10 lower than that for silicon in the same stars. The observations of near-UV lines using the Copernicus V1 tubes with removal of a high cosmic-ray-induced fluorescent background are described.

Barker, E. S.↗
NASA NTRS1982

High resolution observations of magnesium II 2800 A in Alpha Centauri A - The density of interstellar magnesium II and the stellar chromospheric profiles

The profiles are virtually identical with the solar profiles except for the presence of an absorption feature near line center in the h and k lines of Alpha Centauri A. It is found that this absorption feature can be explained by interstellar absorption of Mg II along the line of sight. The average density of Mg II is found to be 2.75 plus or minus 0.7 x 10 to the -7th/cu cm, in good agreement with the previously determined values in the solar vicinity in the direction of Alpha CMa and Alpha Lyr.

Oegerle, W. R.↗
NASA NTRS1980

Radial velocity study of four southern RS CVn candidates and related field stars

Radial velocity variations are demonstrated for four southern RS CVn candidates: HD 39937, 101379, 155555, and 174429. The period of HD 155555 appears to have decreased by about one part in 100,000 over the past 18 yr. In addition, high-resolution observations of the Ca II H and K profiles and the Mg II 2800-A emission doublet are presented. These enhance the likelihood of these being RS CVn objects. Radial velocity data for 15 other late-type bright field stars are presented. Some of these were observed by Copernicus and may exhibit unusual chromospheres, while the rest lack radial velocity information as tabulated in the Bright Star Catalog. All velocity measures have been corrected to the IAU heliocentric system.

Stacy, J. G.↗
NASA NTRS1980

Mercury in a thin layer in HgMn stars - A test of a diffusion model

Lines of the first three states of ionization of mercury have been observed in Mu Leporis and Chi Lupi using the Copernicus satellite. Lines of Hg II and Hg III have been observed in Alpha Andromedae. There appears to be an absorption feature at every wavelength where there is expected to be a mercury line. The presence of all three states of ionization is likely in Mu Lep and Chi Lup. The relative equivalent widths of the lines of the various states of ionization do not depend on the effective temperature of the stars, in contradiction to what is expected if mercury were uniformly distributed in the atmosphere. It is, however, expected if mercury has been concentrated, by diffusion, in a thin layer, where the radiative forces just equal the gravitational forces on mercury. That mercury should be so concentrated is also required by the explanation of the mercury isotope anomaly proposed by Michaud, Reeves, and Charland.

Megessier, C.↗
NASA NTRS1980

A search for the reported Ti II 3080 multiplet emission in late-type stars

Gurzadyan (1975), using a low-resolution objective-prism spectrograph, has reported the presence of both the multiplet Ti II 3080 and the doublet Mg II 2800 simultaneously either in emission or in absorption in late-type stars. Using the high-resolution spectrometers onboard Copernicus and BUSS, it is found that stars which display Mg II 2800 strongly in emission do not have a corresponding emission feature at 3080.

Oegerle, W. R.↗
NASA NTRS1979

Southern RS CVn systems - Candidate list

A list of 43 candidate RS CVn binary systems in the far southern hemisphere of the sky (south of -40 deg declination) is presented. The candidate systems were selected from the first two volumes of the Michigan Spectral Catalog (1975, 1978), which provides MK classifications for southern HD stars and identifies any unusual characteristics noted for individual stellar spectra. The selection criteria used were: (1) the occurrence of Ca II H and K emission; (2) known or suspected binary nature; (3) regular light variations of zero to one magnitude; and (4) spectral type between F0 and K2 and luminosity less than bright giant (II).

Weiler, E. J.↗
NASA NTRS1979

Copernicus observations of neutral hydrogen and deuterium in the direction of HR 1099

High-resolution Copernicus U1 scans were obtained of the bright RS CVn binary HR 1099 (d = 33 pc, galactic longitude = 185 deg, galactic latitude = -41 deg) in October 1977. Strong emission at L-alpha was detected. The interstellar L-alpha absorption features of H I and D I were also observed. Analyses of these interstellar lines are reported in this paper. The average density of neutral H in the direction of this system is found to be 0.006-0.012 per cu cm, which, because the local density is higher, requires a marked inhomogeneity along this line of sight. This result, when combined with other recent studies of the local interstellar medium, suggests the sun is located within a moderate-density H I region.

Anderson, R. C.↗
NASA NTRS1979

A Copernicus survey of Mg II emission in late-type stars

The behavior of Mg II emission in late-type stars is examined using scan data obtained with the Copernicus satellite. The luminosity in the Mg II k emission line was found to be closely related to stellar absolute magnitude, leading to the suggestion that such correlation may be very useful for future UV observations. The stellar surface flux in the k line was observed to be roughly constant or to decrease slowly with later spectral type, a finding which is then used to show that the pressure at the top of the chromosphere decreases with later spectral type, in agreement with the conclusions by McClintock et al. (1975). An asymmetry in the Mg II k line was noticed to be present in the available data for the stars later than K2-K5.

Weiler, E. J.↗
NASA NTRS1978

Copernicus observations of interstellar matter in the direction of HR 1099

Results are reported for high-resolution Copernicus U1 and V2 scans of the bright RS CVn spectroscopic binary HR 1099. The observations reveal strong UV emission lines at L-alpha and Mg II h and k from the stars as well as interstellar H I and D I L-alpha absorption lines and interstellar Mg II h and k absorption in the direction of the binary system. Column densities, bulk velocities, and temperatures are derived for the interstellar features. A comparison of the derived number density of interstellar H I with data for the nearby star Epsilon Eri indicates an inhomogeneous distribution of interstellar hydrogen along the line of sight. The range of values obtained for the D/H ratio is shown to be consistent with results of other studies. A depletion factor of at least 5 with respect to the solar abundance is estimated for the interstellar magnesium.

Anderson, R. C.↗
NASA NTRS1978

Copernicus observations of Ly-alpha and Mg II emission from HR 1099 /V711 Tauri/ and UX Ari

Ultraviolet observations of two RS CVn binaries obtained with Copernicus are described. High-resolution (0.05 A) U1 observations indicate that both HR 1099 and UX Ari display broad Ly-alpha emission. The Ly-alpha emission strength from HR 1099 is variable and seems to be correlated with orbital phase, while the UX Ari results indicate no significant variation. Moderate resolution (0.51 A) V2 scans of both systems show variable Mg II h and k emission-line profiles which usually matched the velocity of the more active star in each binary. Additionally, displaced emission components were seen at velocities of up to + or - 250 km/s, indicative of high-velocity gas motions. The radial velocities of these emission features from HR 1099 are marginally correlated with orbital phase. Highly active and variable chromospheric phenomena are found to be the most consistent explanation of these results.

Weiler, E. J.↗
NASA NTRS1974

LX Persei, an eclipsing binary with H and K emission

The masses and MK classes were calculated for the eclipsing spectroscopic binary LX Persei. Its spectrum shows strong H and K emission and doubled lines in the photographic region. The Ca II emission velocity shifts vary in phase with the secondary's absorption lines and are presumably associated with this component. The stars are tentatively classed as G0 V and K0 IV, and the cooler component is the more massive by a ratio of 0.96. The system has a period of 8.0 days.

Weiler, E. J.↗