Search Publications
Abundance analysis of the hot post-AGB star Barnard 29.
Dufton, P. L.; Keenan, F. P.; Conlon, E. S.
We present a model atmosphere analysis for the relatively bright (V~13) globular cluster post-AGB star, Barnard 29, using IUE and high resolution (0.06A FWHM) optical spectra. The derived atmospheric parameters are T_eff_=20000+/-1000K and logg=3.0+/-0.1dex, which imply a current mass of ~0.55Msun_. The chemical composition provides imp…
WFPC2 Observations of the Globular Cluster M30
Schneider, Donald P.; Yanny, Brian; Bahcall, John N. +1 more
We describe images of the center of the dense globular cluster M30 (NGC 7099) obtained with the Hubble Space Telescope Wide Field/Planetary Camera 2 (HST WFPC2). Data taken in the F336W, F439W, and F555W filters (approximately U, B, and V) yield a color-magnitude diagram with photometric errors of 1 sigma = 0.05 mag for stars with V less than 17.5…
Evidence for a Disk in the Wind of HD 93521: UV Line Profiles from an Axisymmetric Model
Ignace, R.; Bjorkman, J. E.; Cassinelli, J. P. +1 more
Recently it has been suggested (Massa 1992; Howarth & Reid 1993), from the C IV ultraviolet resonance line profile of HD 93521, that there is a high-speed component in the polar outflow from the star as well as a low-speed component in the equatorial regions. In this paper we present theoretical calculations of the line profiles that would be …
The Be Star Gamma Cassiopeiae: X-Ray, Far-UV, and Optical Observations in Early 1989
Murakami, Toshio; Kawai, Nobuyuki; Matsuoka, Masaru +12 more
The state of gamma Cas in early 1989 is presented as the result of joint observations in the X-ray, far-UV, and optical regions. Particular attention has been paid to short- and long-term variations within these spectral ranges. In X-ray observations with the Ginga satellite we have found no specific periodic variabilities in the 64 to 13,000 s ra…
Weak Soft X-Ray Excesses Need Not Result from the High-Frequency Tail of the Optical/Ultraviolet Bump in Active Galactic Nuclei
Czerny, Bozena; Zycki, Piotr T.
The broad-band ROSAT/EXOSAT X-ray spectra of six Seyfert 1 galaxies are fitted by a model consisting of a direct power law and a component due to reflection/reprocessing from a partially ionized, optically thick medium. The reflected spectrum contains emission features from various elements in the soft X-ray range. In all objects but one (Mrk 335)…
Properties of the Highly Ionized Disk and Halo Gas toward Two Distant High-Latitude Stars
Sembach, K. R.; Savage, Blair D.
Goddard High Resolution Spectrograph (GHRS) intermediate -resolution observations of S III, Si III, Al III, Si IV, C IV, and N V absorption along the sight lines to HD 18100 (l = 217.9 deg, b = -62.7, d = 3.1 kpc, z = -2.8 kpc) and HD 100340 (l = 258.9 deg, b = +61.2 deg, d = 5.3 kpc, z = 4.6 kpc) are presented. These small science aperture spectr…
X-ray spectra of a complete sample of extragalactic core-dominated radio sources.
Worrall, D. M.; Brunner, H.; Staubert, R. +1 more
We present ROSAT soft X-ray spectra for the members of a complete sample of 13 core-dominated, flat radio spectrum sources. The sample comprises all radio sources from a flux-limited radio catalog (S_5 GHz_ > 1 Jy; Kuehr et al.) which are north of δ= 70deg, at galactic latitudes b > 10deg, and have a flat radio spectrum between 1.4 and 5 GHz…
The extent of variability in the stellar wind of the O7.5 giant ξ Persei
Kaper, L.; Henrichs, H. F.; Nichols, J. S.
Using high-time-resolution ultraviolet spectroscopy, we present evidence that variability in the stellar wind of the O7.5 III(n)((f)) star ξ Per takes place essentially over the whole velocity range over which the wind is observable in absorption: from ~-100 km/s in the SiIV line up to -2750 km/s in NV and CIV, about 400 km/s beyond the terminal v…
Studies of early-type variable stars. XI. Absolute parameters of the Algol system RZ Cassiopeiae.
Maxted, P. F. L.; Hilditch, R. W.; Hill, G.
A new spectroscopic orbit is presented for the semi-detached eclipsing binary system RZ Cas (HD 17138, P=1.195 days, alpha(2000.0) = 2 h 48.9 m, alpha = +69 deg 38 min, (A3V+KO), based on Reticon observations with the Dominion Astrophysical Observatory (DAO) 1.2 m telescope and coude spectrograph. We find: mp sin 3 i = 2.16 +…
High-Energy Spectra of Active Galactic Nuclei. I. The Catalog
Malaguti, G.; Bassani, L.; Caroli, E.
This paper presents a catalog of high-energy spectra (E >= 0.01 keV) of active galactic nuclei (AGNs). The catalog contains 209 objects (140 Seyfert galaxies, 65 quasars, and 4 objects otherwise classified), for a total of 1030 spectra. Most of the data have been collected from the literature over a period spanning more than 20 yr starting from…