Search Publications
Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Makarov, V. V.; Fabricius, C.
Using observations obtained with the Tycho instrument of the ESA Hipparcos satellite, a two-colour photometry is produced for components of more than 7 000 Hipparcos double and multiple stars with angular separations 0.1 to 2.5 arcsec. We publish 9473 components of 5173 systems with separations above 0.3 arcsec. The majority of them did not have T…
On the source regions of the fast solar wind in polar coronal holes
Wilhelm, K.; Marsch, E.; Dammasch, I. E. +1 more
Fast streams of the solar wind with speeds of up to ~ 800 km s-1 at a distance of 1 AU (astronomical unit) from the Sun are known to originate in solar coronal holes. With the Solar and Heliospheric Observatory (SOHO) detailed studies of the solar wind source regions have been made possible for the first time. We show images of solar po…
The Narrow-Line Regions of LINERS as Resolved with the Hubble Space Telescope
Ho, Luis C.; Maoz, Dan; Eracleous, Michael +1 more
Low-ionization nuclear emission-line regions (LINERs) exist in the nuclei of a large fraction of luminous galaxies, but their connection with the active galactic nucleus (AGN) phenomenon has remained elusive. We present Hubble Space Telescope (HST) narrowband ([O III] λ5007 and Hα+[N II]) emission-line images of the central regions of 14 galaxies …
Turbulent Solar Convection and Its Coupling with Rotation: The Effect of Prandtl Number and Thermal Boundary Conditions on the Resulting Differential Rotation
Toomre, J.; Elliott, J. R.; Miesch, M. S.
The dynamics of the vigorous convection in the outer envelope of the Sun must determine the transport of energy, angular momentum, and magnetic fields and must therefore be responsible for the observed surface activity and the angular velocity profile inferred helioseismically from SOI-MDI p-mode frequency splittings. Many different theoretical tr…
The Contribution of Field OB Stars to the Ionization of the Diffuse Ionized Gas in M33
Hoopes, Charles G.; Walterbos, René A. M.
We present a study of the ionizing stars associated with the diffuse ionized gas (DIG) and H II regions in the nearby spiral galaxy M33. We compare our Schmidt Hα image to the far-ultraviolet (FUV, 1520 Å) image from the Ultraviolet Imaging Telescope (UIT). The Hα/FUV ratio is higher in H II regions than in the DIG, suggesting an older population …
The Formation of Encke Meteoroids and Dust Trail
Reach, William T.; Sykes, Mark V.; Lien, David +1 more
We observed Comet 2P/Encke with the Infrared Space Observatory ISOCAM on July 14, 1997, from a particularly favorable viewing geometry above the comet's orbital plane and at a distance of 0.25 AU. A structured coma was observed, along with a long, straight dust trail. For the first time, we are able to observe the path of particles as they evolve …
Absolute proper motions of open clusters. I. Observational data
Wielen, R.; Dettbarn, C.; Baumgardt, H.
Mean proper motions and parallaxes of 205 open clusters were determined from their member stars found in the Hipparcos Catalogue. 360 clusters were searched for possible members, excluding nearby clusters with distances D < 200 pc. Members were selected using ground based information (photometry, radial velocity, proper motion, distance from th…
The Unusual Infrared Object HDF-N J123656.3+621322
Papovich, Casey; Dickinson, Mark; Ferguson, Henry C. +11 more
We describe an object in the Hubble Deep Field North with very unusual near-infrared properties. It is readily visible in Hubble Space Telescope NICMOS images at 1.6 µm and from the ground at 2.2 µm, but it is undetected (with S/N<~2) in very deep WFPC2 and NICMOS data from 0.3 to 1.1 µm. The fν flux density drops b…
Kinematics of young stars. I. Local irregularities
Figueras, F.; Torra, J.; Fernández, D.
The local velocity field of young stars is dominated by the galactic rotation, the kinematics of the Gould Belt and the nearest OB associations and open clusters, and the kinematics of the spiral structure. We re-examined here this local velocity field by using a large sample of nearby O and B stars from the Hipparcos Catalogue. The high quality a…
On the Globular Cluster Initial Mass Function below 1 Msolar
Paresce, Francesco; De Marchi, Guido
Accurate luminosity functions (LFs) for a dozen globular clusters have now been measured at or just beyond their half-light radius using HST. They span almost the entire cluster main sequence (MS) below 0.75 Msolar. All these clusters exhibit LFs that rise continuously from an absolute I magnitude MI~=6 to a peak at MI