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A Compact Spectral Range and Matching Extreme-Ultraviolet Spectrometer for the Simultaneous Study of 1 × 104-2 × 107 K Solar Plasmas
Doschek, G. A.; Brown, C. M.; Feldman, U. +2 more
An EUV spectral range of less than 100 Å in first order has been found that includes sufficient spectral lines and critical combinations of lines in first and second order to permit dynamic and diagnostic investigations of the solar atmosphere with a relatively simple spectrometer. An optical design of such a spectrometer, based on the performance…
A New Method for Diagnostics of Solar Magnetic Fields and Flows from Time-Distance Analysis
Ryutova, Margarita; Scherrer, Philip
We propose a new method to obtain information on plasma flows and magnetic fields below the visible solar surface using time-distance measurements. The method is based on sine and cosine transforms of propagation times measured as a function of direction. The method allows one to sort out various characteristics of the subsurface medium, the flows…
Photometry from the HIPPARCOS Catalogue: Constant MCP Stars, Comparison and Check Stars
Adelman, S. J.
Photometry from the Hipparcos catalogue is used to verify the constancy of four magnetic CP stars, as well as the comparison and the check stars used for variability studies of normal and chemically peculiar B and A stars with the Four College Automated Photoelectric Telescope; variability in these stars can produce spurious results. A few of the …
Stellar atmospheric parameters for the giant stars MU Pegasi and lambda Pegasi
Smith, G.
Profiles of the strong lines Ca II 8542 Angstroms, and Mg I 8806 Angstroms, together with regions containing Ca I, Fe I and Fe II lines in the spectra of the G8 giant stars mu Peg and lambda Peg have been recorded at high resolution and with signal/noise >= 100. The wings of the strong lines and the full profiles of intermediate strength lines …
On the systematic accuracy of the equatorial UBV standards
Evans, D. W.; Oja, T.
Using photometric data from the TYCHO experiment of the HIPPARCOS mission the discrepancies in B-V between the different series of measurement of the equatorial UBV standards have been studied. Corrections to the data by Landolt (1983) and Menzies et al. (1991) have been derived. based on observations made with the ESA Hipparcos satellite.
Ultraviolet Observations of a Dynamic Event in the Solar Corona
Dwivedi, B. N.; Wilhelm, K.; Curdt, W. +1 more
The Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) observations show high Doppler shifts and temporal variations in profiles of ultraviolet lines from low temperature gas in the corona above the active region NOAA 7974. The profiles indicate ≈ 100 km s-1 flows coming from an almost stationary source that appears …
The stellar content of a spiral arm of NGC 4321
Dolphin, Andrew E.; Hodge, Paul W.; Wyder, Ted K.
The effects of the passage of a spiral arm through the disc of the giant Virgo Sc galaxy NGC 4321 are investigated with Hubble Space Telescope WFPC2 images in two colours. Concentrating on a portion of the southern spiral arm of NGC 4321, we have applied a new program to solve for the star formation histories in the arm and interarm regions separa…
On an ultraviolet spectral atlas of alpha2 CVn
Wahlgren, G. M.
We describe the ultraviolet spectra of the Ap star alpha 2 CVn that have been acquired with the Hubble Space Telescope and the nature of the optical region analyses for its rotational velocity and elemental abundances that have been undertaken in support of the ultraviolet data.
The new astrometry
Kovalevsky, J.
First, the main objectives of astrometry are presented and the most important features or phenomena that intervene in the measurement of positions of celestial objects are shortly described. Then, the two classical astrometric techniques that are still very much used, especially since the invention of CCDs, transit instrument and astrophotography,…
Low energy anomalous ions at northern heliolatitudes
Lanzerotti, L. J.; Maclennan, C. G.
Measurements of the anomalous component of nitrogen, oxygen, and neon ions (∼0.5-8 MeV/nucl.) at northern heliolatitudes by the HI-SCALE instrument on the Ulysses spacecraft show that the energy spectra of these ions are essentially flat from the highest heliolatitudes (80° N) to near the ecliptic plane. For energies from 1-8 MeV/nucl., the northe…