Search Publications
The Location of the Nucleus of NGC 1068 from HST Imaging Polarimetry and Absolute Astrometry
Macchetto, F. D.; Capetti, A.; Lattanzi, M. G.
We present the results of a program to obtain an accurate (better than 100 mas) astrometry of HST images of NGC 1068 and consequently a direct registration with radio images. The optical peak seen in the HST images is located at α = 02h42m40.711s, δ = -00°00'47.81 (J2000, FK5), with an error of 80 mas. The hidden nucleus, as determined by HST imag…
Absolute proper motions for the calibration of the HIPPARCOS proper motion system
Klemola, A. R.; Geffert, M.; Schmoll, J. +1 more
Absolute proper motions of 48 Hipparcos stars in nine fields distributed over the northern hemisphere are presented. The proper motions have been recently used as part of the Bonn program for the extragalactic link of the Hipparcos proper motion system. We describe methods which have led to the absolute proper motions of the major part of the Bonn…
Discovery of CI around 51 Ophiuchi.
Deleuil, M.; Ferlet, R.; Vidal-Madjar, A. +6 more
We present the discovery of cold CI in the 51 Oph environment, with a column density of N=5x10^13^cm^-2^ and temperature T=~20K. This is the first β Pic-like star other than β Pic with simultaneous detection of cold dust and gas. The CI/infrared continuum ratio and consequently the gas/dust ratio are similar to the β Pic ones. Since CI has a very …
Energetic electron beams in the duskside Jovian magnetosphere: Ulysses EPAC and HI-SCALE measurements
Krupp, N.; Woch, J.; Dougherty, M. K. +4 more
The Ulysses flyby of Jupiter in February 1992 provided the first opportunity to investigate the high southern latitudes of the dusk side magnetosphere. We combine measurements taken by the Ulysses energetic particle instruments EPAC and HI-SCALE and identify bi-directional, field-aligned electron beams in an energy range from 100-380 keV. The beam…
The Surface Brightness Fluctuations and Globular Cluster Population of NGC 4478
Ford, Holland C.; Tsvetanov, Zlatan I.; Neilsen, Eric H., Jr.
We calculate the distance to NGC 4478, a neighbor of the giant Virgo elliptical M87, using the surface brightness fluctuations method on parallel data from the HST WFPC2 camera. The exposures considered were taken through the F814W filter, which approximates the Johnson I, and through the F606W filter, which is effectively a broad V filter. We des…
Stellar activity and the Wilson-Bappu relation.
Engvold, O.; Elgaroy, O.; Joras, P.
The MgII h and k lines of 78 single stars observed with the International Ultraviolet Explorer (IUE) observatory have been analyzed. Stars of spectral classes F, G, K and M and luminosity classes I-V are represented in the sample. From these data it is shown that the Wilson-Bappu relation for the Mg II h and k lines is fulfilled over a range of 18…
Detectability of High-Redshift Elliptical Galaxies in the Hubble Deep Field
Maoz, Dan
Relatively few intensively star-forming galaxies at redshifts of z>2.5 have been found in the Hubble Deep Field (HDF). This has been interpreted to imply a low space density of elliptical galaxies at high z, possibly due to a late (z<2.5) epoch of formation or to dust obscuration of the ellipticals that are forming at z~3. I use Hubble Space…
Ulysses solar wind plasma observations at high latitudes
McComas, D. J.; Goldstein, B. E.; Bame, S. J. +7 more
Ulysses reached its peak northerly heliolatitude of 80.2 degN on July 31st, 1995, and is now moving towards aphelion at 5.41 AU which it will reach in May, 1998. We summarize measurements from the solar wind plasma experiment, SWOOPS, emphasizing northern hemispheric observations but also providing southern and equatorial results for comparison. T…
Abundances and Depletions toward the Orion Nebula
Snow, Theodore P.; Shuping, R. Young
This paper presents an absorption-line study of θ1 C Orionis (HD 37022), based on IUE data. The line of sight, as determined by O'Dell et al. (1993), is thought to consist of two major cloud complexes: the ``neutral lid'' and some foreground material. A key challenge was to improve the S/N for IUE spectra, and this is discussed in some …
Observations of the wind of the old nova V603 Aquilae with the HST-GHRS.
Selvelli, P.; Friedjung, M.; Cassatella, A.
High resolution spectra of the old nova V603 Aql (1918) were taken in the regions of the C IV, N V and Si IV resonance doublets, using the G160M grating of the GHRS on board the Hubble Space Telescope. No sign of sharp absorption components due to the envelope ejected in 1918 is present. If spherical symmetry is assumed, the estimated upper limits…