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EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO - I. Line Emission and Time Dependence
Harrison, R. A.; Wilhelm, K.; Fredvik, T. +8 more
EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981, were obtained on 2 August 1996 with the Coronal Diagnostic Spectrometer (CDS) and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on the Solar and Heliospheric Observatory (SOHO). The spectral lines formed in the transition region and corona show considerable str…
Eclipsing phenomena of the symbiotic star CH Cygni
Iijima, Takashi
Eclipsing phenomena of the inner binary with a period of 756 d in the triple symbiotic system CH Cyg may have been detected in detailed spectrophotometric observations. The eclipse of the hot component by the red giant started on 1994 October 11 and finished between 1995 January 8 and 18. The ingress duration was less than one day. The radius of t…
The Complete Spectral Energy Distribution and the Atmospheric Properties of the Helium-Rich White Dwarf MCT 0501-2858
Vennes, Stéphane; Polomski, Elisha F.; Chayer, Pierre +3 more
We analyze high-dispersion ultraviolet spectroscopic observations of the peculiar helium-rich white dwarf MCT 0501-2858. Ultraviolet spectra obtained during the 1996 November ORFEUS-SPAS II mission show the complete He II (n=2) line series as well as narrow heavy-element lines; the spectrum constrains the effective temperature (68,600 +/- 1800 K) …
Solid CO_2 towards NGC7538 IRS1
Leto, G.; Strazzulla, G.; Nisini, B. +2 more
We report the observation of the young infrared source NGC7538 IRS1 with the Short Wavelength Spectrometer (SWS) onboard the ISO satellite in the 2.4-45 mu m range. The spectrum exhibits several absorption features due to silicates and to molecular species frozen on the refractory dust. In particular the stretching and bending mode of solid CO_2 h…
The HR 1614 Group and HIPPARCOS Astrometry
Eggen, Olin J.
The evidence for the existence of the important HR 1614 supercluster and group of rare rich CN stars is examined with the use of Hipparcos astrometry. Group membership is supported by Hipparcos parallaxes except for two stars for which available evidence suggests uncertainty in the Hipparcos values.
An Absence of Gaps in the Main-Sequence Population of Field Stars
Yanny, Brian; Newberg, Heidi Jo
Using high-precision parallaxes from the Hipparcos catalog, we construct H-R diagrams for two samples of bright stars. The first is a magnitude-limited sample that is over 90% complete and uses uniform photometry from the Catalog of WBVR Magnitudes of Northern Sky Bright Stars (δ>-14deg). This sample shows a smooth distribution of st…
Interplanetary Lyman α remote sensing with the Ulysses Interstellar Neutral Gas Experiment
Pryor, Wayne R.; Ajello, Joseph M.; Witte, Manfred
The Ulysses neutral gas instrument obtained celestial sphere maps of interplanetary Lyman α emission from neutral hydrogen in 1991-1996. These maps are unique because the spacecraft was located at a wide range of heliocentric ecliptic latitudes. Eleven of these maps are compared with the predictions of an interstellar wind hydrogen model previousl…
HIPPARCOS based astrometric analysis of M 3 and M 92 fields: optical identification of X-ray and radio sources, space motions of globular clusters M 3 and M 92 and a galactic orbit of the sdB star PG 1716+426
Geffert, M.
We present positions and proper motions with respect to the Hipparcos system of stars in the fields of the globular clusters M 3 and M 92. The data were used for the optical identification of X-ray and radio sources, a new determination of the absolute proper and space motions of the globular clusters M 3 and M 92. Moreover, we derived an accurate…
Lyalpha absorption in the nearby Universe: the sightline to Q1821+643
Bowen, David V.; Pettini, Max; Boyle, Brian J.
We present the first results of a survey designed to understand the origin of Lyalpha-forest absorption systems at low redshift. Using the WYFFOS and HYDRA multifibre spectrographs on the William Herschel and Wisconsin Indiana Yale NOAO (WIYN) telescopes, we have identified 51 galaxies brighter than b_j:=:18.5 within 30 arcmin of the sightline of …
Tentative Detection of Circumstellar CO2 from the AGB Star R Crateris
Ryde, N.; Eriksson, K.; Gustafsson, B. +2 more
We report on and discuss the detection of an emission feature at 14.98 µm from the oxygen-rich, semi-regularly pulsating Asymptotic Giant Branch star R Crateris, a feature which we suggest to be due to the <Stack> 0 1 </Stack> Q-branch of circumstellar CO2. We also suggest a reasonable excitation mechanism, which …