Search Publications
EK TrA, a close relative of VW HYI
Gänsicke, B. T.; Beuermann, K.; Thomas, H. -C.
The southern dwarf nova EK TrA has been suggested to show the spectrum of its white dwarf primary in the single available International Ultraviolet Explorer (IUE) post-outburst spectrum. We demonstrate that this spectrum is still disc-dominated. However, a careful analysis reveals a white dwarf contribution of ~25 per cent of the SWP flux and a wh…
The Color-Magnitude Diagram in Baade's Window Revisited
Kiraga, Marcin; Paczyński, Bohdan; Stanek, Krzysztof Z.
We have reanalyzed the OGLE V and I photometry of ~500,000 stars in Baade's Window, and we confirm the extinction map published by Stanek. However, we find that the interpretation of the OGLE color-magnitude diagram for the disk stars proposed by Paczyński et al. was incorrect: the dominant disk population in Baade's Window is old, and we find no …
Final Astro-1 Calibration of the Hopkins Ultraviolet Telescope: A Test of White Dwarf Model Atmospheres as Far-Ultraviolet Calibration Standards
Kriss, Gerard A.; Holberg, J. B.; Kimble, Randy A. +5 more
We present the final calibration of the Hopkins Ultraviolet Telescope (HUT) for its flight during the Astro-1 space shuttle mission in 1990 December. The calibration is defined by a comparison between an observation obtained in flight of the hot DA white dwarf G191-B2B and the model atmosphere for this star calculated by P. Bergeron. We also prese…
The nature of the broad-line region in the radio-loud active galactic nucleus 3C 390.3
Schartel, Norbert; Wamsteker, Willem; Wang, Ting-Gui +1 more
We present the results of an analysis of the ultraviolet and X-ray variability of the broad-line radio (BLR) galaxy 3C 390.3 over 15 years. The ultraviolet (UV) continuum of 3C 390.3 shows large variations with amplitudes of up to a factor of 10. We find the following results. (1) The variations of Civ and Lyalpha are highly correlated with the UV…
The Mass and Radius of 40 Eridani B from HIPPARCOS: An Accurate Test of Stellar Interior Theory
Provencal, J. L.; Shipman, H. L.; Thejll, P. +1 more
The astrometric satellite HIPPARCOS has determined the distance to the important white dwarf 40 Eridani B with an accuracy surpassing 1%. We use this datum to redetermine the mass and radius of this star and find that M = 0.501 +/- 0.011 Msolar and R = 0.0136 +/- 0.00024 Rsolar. These values, the most accurately determined ma…
Search for brightness fluctuations in the zodiacal light at 25 MU M with ISO
Abraham, Peter; Lemke, Dietrich; Leinert, Christoph
We mapped at 25 mu m five ~0.5(deg) x0.5(deg) fields at low, intermediate and high ecliptic latitude with the photometer onboard the Infrared Space Observatory. The goal was to search for potential structures in the zodiacal light. No structures were seen in these five sample fields. For an aperture of 3' diameter we find an upper limit for the un…
Local interstellar cloud electron density from magnesium and sodium ionization: a comparison.
Ferlet, R.; Lallement, R.
The ambient interstellar plasma density (i.e. the plasma density of the interstellar medium surrounding the Sun) directly governs the structure and the size of our heliosphere. Information on this density can be derived from the ionization states of the interstellar species which can be detected in absorption along the paths to the nearby stars, a…
Detection by ISO of the far-infrared OH maser pumping lines in IRC+10420
Barlow, M. J.; Liu, X. -W.; Cox, P. +8 more
The population inversions which lead to circumstellar hydroxyl (OH) maser emission from cool stars have long been thought to be radiatively pumped. However, the proposed pumping mechanism has not been directly observed before now, because the spectral lines that correspond to the rotational transitions of the pumping cycle lie in the far-infrared,…
The neon abundance in WC stars - I. ISO SWS spectroscopy of WR146 (WC6+O)
Crowther, P. A.; Willis, A. J.; Morris, P. W. +4 more
We present infrared spectroscopy in the wavelength range 2.6-20mum of the WC6+O binary system WR146 (MR112) obtained with the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO). These data are combined with ground-based optical (INT) and near-IR (UKIRT) spectroscopy and theoretical continuum distributions revealing E(B-V) …
High-Resolution X-Ray Image of the Hydrogen-deficient Planetary Nebula Abell 30
Chu, You-Hua; Chang, Thomas H.; Conway, Gail M.
Abell 30 is the brighter of only two planetary nebulae that show extended X-ray emission. Our recent ROSAT high-resolution imager observation of A30 reveals a central source at a 4 σ level and emission knots at a 2 σ level. These emission features are within the same region as the H-deficient knots and filaments resolved in a previous HST WFPC2 [O…