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Supra-Horizontal-Branch Stars and Population Gradients in the Galactic Center Globular Cluster NGC 6522
Rich, R. M.; King, I. R.; Paresce, F. +3 more
We have imaged the core of NGC 6522 and an adjacent field 1' north in the U and B passbands using the (pre-COSTAR) HST Planetary Camera. We find 13 stars located 1.5 mag above the horizontal branch. These supra-horizontal-branch (SHB) stars have not been noted previously in NGC 6522, although they occur in other globular clusters. The SHB stars' r…
A Lower Limit to the Distance of High-Velocity Cloud Complex H
Wakker, Bart; van Woerden, Hugo; de Boer, Klaas S. +1 more
We derive a lower limit for the distance of the high-velocity cloud (HVC) complex H, which is a structure covering 480 square degrees on the sky and is centered on l = 131°, b = 1°. Considering the uncertainties in the derivation of stellar distances, we find that the distance to the HVC is certainly larger than 3.4 kpc, probably larger than 5 kpc…
An estimation of the mass of asteroid 20-Massalia derived from the HIPPARCOS minor planets data
Bange, Jeff
The ESA astrometry satellite Hipparcos has observed a set of 48 minor planets between 1989 and 1993. A close encounter between 20-Massalia and 44-Nysa, both planets observed by Hipparcos, enabled us to obtain a value for the mass of 20-Massalia. Due to another close approach with the large asteroid 4-Vesta, the value we obtained (2.42 +/- 0.41 10(…
Hipparcos Observations of Hydrogen-deficient Carbon Stars *
Cottrell, P. L.; Lawson, W. A.
Parallax measurements for 21 hydrogen-deficient carbon stars have been made by the Hipparcos satellite. These stars include most of the brighter R Coronae Borealis (RCB) variables, other cool hydrogen-deficient carbon (HdC) stars, and several higher-T eff extreme helium (eHe) stars. Most of these stars have either negative or statistica…
The Remarkable Boron-depleted, Lithium-normal Population II Star HD 160617
Primas, F.; Duncan, D. K.; Thorburn, J. A.
We present results of an analysis of the boron spectral region (2500 Å) in the metal-poor star HD 160617, observed with the Goddard High Resolution Spectrograph of the Hubble Space Telescope. HD 160617 has a metallicity of [Fe/H]~-1.8, a Teff~5900 K, and a log g ~ 3.5. Its Li abundance is the normal, primordial ``Spite plateau'' value l…
HIPPARCOS absolute magnitudes for metal-rich K giants and the calibration of DDO photometry
Flynn, Chris; Hog, Erik
Parallaxes for 581 bright K giants have been determined using the Hipparcos satellite. We combine the trigonometric parallaxes with ground-based photometric data to determine the K giant absolute magnitudes. For all these giants, absolute magnitude estimates can also be made using the intermediate-band photometric David Dunlop Observatory (DDO) sy…
The Goddard High Resolution Spectrograph: Post-COSTAR Characteristics
Savage, B. D.; Ebbets, D. C.; Carpenter, K. G. +16 more
We review changes to the characteristics of the Goddard High Resolution Spectrograph (GHRS) which resulted from the installation of the Corrective Optics Space Telescope Axial Replacement (COSTAR) on the Hubble Space Telescope. The introduction of two new optical elements into the light path altered the spectral distribution of the light, decreasi…
Repetitive structure in the stellar wind of HD 93843: a normal O-type star
Howarth, Ian D.; Massa, Derck; Prinja, Raman K. +1 more
We present the results from a 28-day IUE time-series campaign monitoring the stellar wind of the O5-type giant HD 93843. The principal aim was to study variability in the wind of a star with a normal projected rotation velocity. Systematic changes are identified, amidst continuous line-profile variability, in the absorption troughs of the Siiv and…
Boron in the very metal-poor star BD -13 3442
Deliyannis, Constantine P.; Primas, F.; Rebull, L. M. +5 more
The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to observe the boron 2500 Angstroms region of BD -13 3442. At a metallicity of [Fe/H]=-3.00 this is the most metal-poor star ever observed for B. Nearly 26 hours of exposure time resulted in a detection. Spectrum synthesis using the latest Kurucz mode…
ASCA observation of the polar RX J1802.1+1804
Greiner, J.; Motch, C.; Ishida, M. +1 more
We present X-ray data of {RX J1802.1+1804} obtained by {ASCA}. Although it shows a clear orbital intensity modulation with an amplitude of nearly 100% below 0.5 keV in {ROSAT} data, the {ASCA} light curves are nearly flat except for a possible dip lasting about one-tenth of the orbital period. We discuss this within the model assumption of a strea…