Search Publications
Missions
Journals
Publication Years
A catalogue of symbiotic stars
Ivison, R. J.; Munari, U.; Friedjung, M. +2 more
We present a new catalogue of symbiotic stars. In our list we include 188 symbiotic stars as well as 30 objects suspected of being symbiotic. For each star, we present basic observational material: coordinates, V and K magnitudes, ultraviolet (UV), infrared (IR), X-ray and radio observations. We also list the spectral type of the cool component, t…
Mid-infrared diagnostics to distinguish AGNs from starbursts
Cesarsky, C.; Madden, S. C.; Sauvage, M. +5 more
We present new mid-infrared (MIR) diagnostics to distinguish emission of active galactic nuclei (AGN) from that originating in starburst regions. Our method uses empirical spectroscopic criteria based on the fact that MIR emission from star forming or active galaxies arises mostly from HII regions, photo-dissociation regions (PDRs) and AGNs. The a…
Toward High-Precision Astrometry with WFPC2. I. Deriving an Accurate Point-Spread Function
Anderson, Jay; King, Ivan R.
The first step toward doing high-precision astrometry is the measurement of individual stars in individual images, a step that is fraught with dangers when the images are undersampled. The key to avoiding systematic positional error in undersampled images is to determine an extremely accurate point-spread function (PSF). We apply the concept of th…
Relationship of halo coronal mass ejections, magnetic clouds, and magnetic storms
Thompson, B. J.; Webb, D. F.; Crooker, N. U. +2 more
Halo coronal mass ejections (CMEs) had been rarely reported in coronagraph observations of the Sun before the Solar and Heliospheric Observatory (SOHO) mission. Since mid-1996, however, the SOHO Large Angle Spectrometric Coronagraph (LASCO) instruments have observed many halo or partial-halo CMEs. A halo CME, especially when associated with solar …
Disks, Microjets, Windblown Bubbles, and Outflows in the Orion Nebula
O'Dell, C. R.; Bally, John; McCaughrean, Mark J.
New deep narrowband images of the Orion Nebula obtained with WFPC2 on the Hubble Space Telescope (HST) and spectra taken with the HIRES spectrometer at the Keck Observatory are presented. We report eight new circumstellar disks seen in silhouette against the background nebular light and about 30 dark disks embedded within the bright proplyds rimme…
The local density of matter mapped by Hipparcos
Flynn, Chris; Holmberg, Johan
We determine the velocity distribution and space density of a volume-complete sample of A and F stars, using parallaxes and proper motions from the Hipparcos satellite. We use these data to solve for the gravitational potential vertically in the local Galactic disc, by comparing the Hipparcos measured space density with predictions from various di…
X-ray photoionized plasma diagnostics with helium-like ions. Application to warm absorber-emitter in active galactic nuclei
Porquet, D.; Dubau, J.
We present He-like line ratios (resonance, intercombination and forbidden lines) for totally and partially photoionized media. For solar plasmas, these line ratios are already widely used for density and temperature diagnostics of coronal (collisional) plasmas. In the case of totally and partially photoionized plasmas, He-like line ratios allow fo…
Models for Old, Metal-poor Stars with Enhanced α-Element Abundances. I. Evolutionary Tracks and ZAHB Loci; Observational Constraints
VandenBerg, Don A.; Alexander, David R.; Swenson, Fritz J. +2 more
Stellar evolutionary tracks have been computed for 17 [Fe/H] values from -2.31 to -0.30 assuming, in each case, [α/Fe]=0.0, 0.3, and 0.6. The helium abundance was assumed to vary from Y=0.2352 at [Fe/H]=-2.31 to Y=0.2550 at [Fe/H]=-0.30 and held constant for the different choices of [α/Fe] at a fixed iron content. Masses in the range 0.5<=M
On the Nature of Soft X-Ray Weak Quasi-stellar Objects
Brandt, W. N.; Laor, A.; Wills, Beverley J.
Recent studies of quasi-stellar objects (QSOs) with ROSAT suggest the existence of a significant population of soft X-ray weak QSOs (SXW QSOs) where the soft X-ray flux is ~10-30 times smaller than in typical QSOs. Why are these QSOs soft X-ray weak, and what is their relationship to broad absorption line QSOs (BAL QSOs) and X-ray warm absorber QS…
Discovery of DampedLyα Systems at Redshifts Less than 1.65 and Results on Their Incidence and Cosmological Mass Density
Turnshek, David A.; Rao, Sandhya M.
We present results from an efficient, nontraditional survey to discover damped Lyα (DLA) absorption systems with neutral hydrogen column densities NHI>=2×1020 atoms cm-2 and redshifts z<1.65. In the past, identification of DLA systems at z<1.65 has been difficult because of their rare incidence and the nee…