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In-Flight Performance of the Virgo Solar Irradiance Instruments on SOHO
Dewitte, Steven; Chevalier, André; Fröhlich, Claus +7 more
The in-flight performance of the total and spectral irradiance instruments within VIRGO (Variability of solar IRradiance and Gravity Oscillations) on the ESA/NASA Mission SOHO (SOlar and Heliospheric Observatory) is in most aspects better than expected. The behaviour during the first year of operation of the two types of radiometers and the sunpho…
First Hubble Space Telescope Observations of Mira AB Wind-accreting Binary Systems
Raymond, John; Karovska, Margarita; Guinan, Edward +1 more
The Mira AB system belongs to a class of detached binaries in which a compact object accretes mass from the wind of a cool giant or supergiant. This system provides a unique laboratory for detailed study of the characteristics of the wind accretion processes because it can be spatially resolved with the Hubble Space Telescope (HST) and the compone…
The Evolution of the Final Helium Shell Flash Star V605 Aquilae From 1917 to 1997
De Marco, Orsola; Clayton, Geoffrey C.
Only three stars have been observed going through a final helium shell flash since the advent of modem instrumentation, FG Sagittae (in 1894), V605 Aquilae (in 1919), and Sakurai's Object (in 1996). In this paper, we present for the first time a spectrum taken of V605 Aql, while it was in its cool giant phase in 1921. This spectrum is identical to…
Hubble Space Telescope Observations of the Post-Core-Collapse Globular Cluster NGC 6752. II. A Large Main-Sequence Binary Population
Bailyn, Charles D.; Rubenstein, Eric P.
We present a color-magnitude diagram (CMD) of NGC 6752 based on post-refurbishment Planetary Camera 2 observations of its core. The main sequence is broadened and asymmetric, as would be expected if there were large numbers of binary stars. We use artificial star experiments to characterize the broadening of the main sequence that is expected, due…
The HIPPARCOS proper motion of the Magellanic Clouds
Kroupa, Pavel; Bastian, Ulrich
The proper motion of the Large (LMC) and Small (SMC) Magellanic Cloud using data acquired with the Hipparcos satellite is presented. Hipparcos measured 36 stars in the LMC and 11 stars in the SMC. A correctly weighted mean of the data yields the presently available most accurate values, µαcos( δ) = 1.94±0.29 mas/yr, µδ<…
Evaluating Possible Heating Mechanisms Using the Transition Region Line Profiles of Late-Type Stars
Ayres, Thomas R.; Wood, Brian E.; Linsky, Jeffrey L.
Our analysis of high-resolution Goddard High-Resolution Spectrograph (GHRS) spectra of late-type stars shows that the Si IV and C IV lines formed near 105 K can be decomposed into the sum of two Gaussians, a broad component and a narrow component. We find that the flux contribution of the broad components is correlated with both the C I…
HST, radio and infrared observations of 28 3CR radio galaxies at redshift z~ - I. The observations
Best, P. N.; Longair, M. S.; Roettgering, H. J. A.
Hubble Space Telescope images are presented of a sample of 28 3CR radio galaxies with redshifts in the range 0.6<z<1.8, together with maps at comparable angular resolution of their radio structure, taken using the Very Large Array. Infrared images of the fields, taken with the United Kingdom InfraRed Telescope, are also presented. The optica…
The LINER Nucleus of M87: A Shock-excited Dissipative Accretion Disk
Dopita, Michael A.; Sutherland, Ralph S.; Ford, Holland C. +4 more
We present long-baseline Faint Object Spectrograph (FOS) spectra of the nuclear accretion disk in M87 (NGC 4486), offset from the nucleus by 0.6" (42.7 pc) in order to avoid the nuclear continuum. Even so close to the nucleus, the optical spectrum has the appearance of a normal LINER galaxy. We show that the presence of strong UV emission lines pr…
Absorption by Highly Ionized Interstellar Gas Along Extragalactic and Galactic Sight Lines
Sembach, Kenneth R.; Savage, Blair D.; Lu, Limin
We present intermediate resolution (FWHM ∼10-20 km s-1) Goddard High Resolution Spectrograph observations of Galactic C IV and N V absorption along the sight lines to Fairall 9, Mrk 509, PKS 2155-304, and NGC 5548. These observations also provide measures of Si II and S II along the sight lines. Recent measurements of Si IV absorption f…
Planetary Nebulae in the Globular Cluster PAL 6 and NGC 6441
Henry, R. B. C.; Kwitter, K. B.; Morse, Jon A. +2 more
Jacoby & Fullton (1998, in preparation) recently surveyed the Galactic globular cluster system for planetary nebulae and identified excellent candidates in the disk clusters Pal 6 and NGC 6441. Velocities, abundances, and central star properties for these two nebulae are derived. There is a 0.5% probability that the nebula in Pal 6 is a chance…