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Elemental abundances for Nova LMC 1990#1
Shore, Steven N.; Sonneborn, George; Starrfield, Sumner +1 more
We present our analysis of the UV spectra of the fast ONeMg Nova LMC 1990#1. Observations with the IUE began on 1990 January 18 and continued through to 1990 March 15. We have analysed these spectra, and determined line fluxes and physical parameters as a function of time. Using both Heii lines and the Balmer decrement, we find the reddening for t…
The integrated magnetic field of the Sun as seen by GOLF on board SOHO
García, R. A.; Turck-Chièze, S.; Ulrich, R. K. +7 more
An objective of the GOLF experiment (Global Oscillations at Low Frequencies) on-board the SOHO (Solar and Heliospheric Observatory) space mission was to measure the line-of-sight component of the disk-averaged magnetic field of the Sun. In this paper, a theoretical study of this observable is presented. The newly developed techniques are tested us…
Kinematics and age of stellar populations in the solar neighbourhood from Hipparcos data
Badiali, M.; Cardini, D.; Emanuele, A. +3 more
The large sample of main sequence stars with Hipparcos parallaxes and estimates of the radial velocity has been used to study the relations among kinematics, age and heavy element content for the solar neighbourhood. The samples with V > -30 km s-1, although including stars as old as 1010 yr, have a very young component (a…
Analysis of UV and optical spectra of the helium-rich white dwarfs HS 2253+8023 and GD 40
Reimers, D.; Heber, U.; Koester, D. +2 more
HS 2253+8023 is a helium-rich white dwarf with traces of metals and hydrogen, which was recently discovered in the Hamburg Quasar Survey. We have derived temperatures and element abundances from optical and UV spectra by comparison with synthetic line profiles. In addition UV (HST, IUE) and optical spectra of the well-known white dwarf GD 40 with …
Radial evolution of density structure in the solar corona
Habbal, Shadia Rifai; Woo, Richard
White-light measurements made by the SOHO coronagraphs (LASCO for Large Angle Spectrometric Coronagraph) and the HAO Mauna Loa Mk III K-coronameter are combined to follow the evolution of path-integrated density structure in the solar corona overlying both coronal hole and quiet Sun regions from 1.15 to 5.5 Ro. The global imaging provid…
The Quasar Pair Q1634+267A,B and the Binary QSO versus Dark Lens Hypotheses
Peng, C. Y.; Keeton, C. R.; Kochanek, C. S. +6 more
Deep HST/NICMOS H-band (F160W) observations of the z=1.96 quasar pair Q1634+267A and B reveal no signs of a lens galaxy to a 1 σ threshold of ~=22.5 mag. The minimum luminosity for a normal lens galaxy would be a 6L* galaxy at z~=0.5, which is 650 times greater than our detection threshold. Our observation constrains the infrared mass-to-light rat…
Improved analysis of interplanetary HST-H_Ly\alpha spectra using time-dependent modelings
Fahr, Hans J.; Bzowski, Maciej; Scherer, Horst +1 more
During a period of 18 months 5 Hubble-Space-Telescope GHRS interplanetary H_{Lyalpha } glow spectra were obtained at different lines of sight from different positions of the earth on its orbit, but despite employment of a radiation transport model that takes into account the angle-dependent partial frequency redistribution, the self-absorption by …
A Hubble Space Telescope Study of Two HII Regions in NGC 6822
O'Dell, C. R.; Hodge, Paul W.; Kennicutt, Robert C., Jr.
We report on the study of the Hubble V and Hubble X H II regions in NGC 6822 with the Hubble Space Telescope employing emission-line and stellar filters. Calibration was made for both data sets, providing magnitudes for the stars and surface brightnesses for the nebulae. The forms of these H II regions are shown to be decidedly more complex than r…
Grain populations in the M 17 south-west star forming complex
Léger, A.; Rouan, D.; Giard, M. +3 more
The different spectral components of the 3-12 mu m dust emission are imaged in the M 17 south-west molecular cloud / Hriptsize{II} region interface. The various images result from a combination of space borne (ISO) and ground based (CFHT) observations. A spatial correlation analysis shows that there are two main components, which correspond to the…
The outer atmosphere of Tau - II. Fluorescent lines
Carpenter, K. G.; McMurry, A. D.; Jordan, C.
The Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope has been used to observe α Tau (K5 III). The resulting spectra contain many sharp fluorescent lines. Most of these have been identified as lines of Fe ii, Ca ii and H2, radiatively excited by H Lyα. The chromospheric model developed in an accompanying paper ha…