Search Publications
Solar Wind and Chromospheric Network
Tu, C. -Y.; Marsch, E.
A physical model of the transition region, including upflow of the plasma in magnetic field funnels that are open to the overlying corona, is presented. A numerical study of the effects of Alfvén waves on the heating and acceleration of the nascent solar wind originating in the chromospheric network is carried out within the framework of a two-flu…
Fundamental Stellar Parameters of γ2 Velorum from HIPPARCOS Data
Schaerer, Daniel; Schmutz, Werner; Grenon, Michel
We report parallax measurements by the HIPPARCOS satellite of γ2 Velorum and a few related objects. The distance of γ2 Vel is d = 258+41-31 pc, significantly smaller than the commonly adopted value to Vela OB2. For ζ Puppis d = 429+120-77 pc is in agreement with the canonical distan…
The distinction between OIafpe and WNLha stars. A spectral analysis of HD 151804, HD 152408 and HDE 313846.
Crowther, P. A.; Bohannan, B.
From detailed atmospheric analysis of the Galactic late O supergiants, HD 151804 (O8Iaf) and HD 152408 (O8:Iafpe) and the morphologically related Wolf-Rayet star, HDE 313846 (WR108; WN9ha) we conclude that little distinguishes the overall structure and composition of the stellar atmosphere of HD 152408 from HDE 313846, such that HD 152408 could be…
Observations of Polar Plumes with the SUMER Instrument on SOHO
Wilhelm, K.; Schühle, U.; Lemaire, P. +1 more
We present new observations of O vi 1032 Å line profiles in polar plumes, and inter-plume regions, on the disk and above the limb in the north coronal hole obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on the SOHO (Solar and Heliospheric Observatory) spacecraft. On 22 May 1996, a 5 x 5 arc min spectroheli…
Double star data in the HIPPARCOS Catalogue
Badiali, M.; Pannunzio, R.; Arenou, F. +12 more
The Hipparcos Catalogue contains astrometric results for 117955 catalogue entries, many of which are in reality double or multiple stars. For 17917 entries special solutions were made in order to cope with the various manifestations of multiplicity, and 6763 other entries were flagged as suspected binaries but solved as single stars. Details of th…
HST Observations and Models of the Gravitational Lens System MG 0414+0534
Falco, Emilio E.; Lehar, Joseph; Shapiro, Irwin I.
Quadruple gravitational lens systems offer the possibility of measuring time delays for image pairs, microlensing effects, and extinction in distant galaxies. Observations of these systems may be used to obtain estimates of H0 and to study the various mass components of lens galaxies at high redshifts. With the Hubble Space Telescope, w…
Bursts of Explosive Events in the Solar Network
Wilhelm, K.; Innes, D. E.; Brekke, P. +1 more
Observations of the quiet-Sun network in the UV emission line Siiv 1393 Å over a time period of two hours are presented. Bursts of explosive events, highly Doppler-shifted emission, seem to be sporadically emitted from the brighter regions of the network lanes. Individual events have typical lifetimes of ≈ 1-6 min and come in bursts of up to 30 mi…
A Survey for Large-Image Separation Lensed Quasars
Maoz, Dan; Rix, Hans-Walter; Gould, Andrew +1 more
The statistics of gravitationally lensed quasars with multiple images in the 0.1"-7" range have been measured in various surveys. Little is known, however, about lensed-quasar statistics at larger image separations, which probe masses on the scale of galaxy clusters. We extend the results of the Hubble Space Telescope (HST) Snapshot Survey for Len…
ISOCAM 7 micron deep survey of the Lockman Hole: A mid-infrared search for primeval galaxies
Sanders, D. B.; Kawara, K.; Taniguchi, Y. +11 more
We present results of our 7 mu m deep survey program made with ISOCAM, the infrared camera of ISO (Infrared Space Observatory). We have found 15 sources above a 5 sigma_rms significance in a small selected area (3(') x 3(') ) in the Lockman HI hole. Among the 15 sources, 14 objects have also been observed in the near infrared (NIR: ~ 2 mu m). The …
First results from UVCS/SOHO
Romoli, M.; Raymond, J. C.; Naletto, G. +20 more
We present here the first results obtained by the Ultraviolet Coronagraph Spectrometer (UVCS) operating on board the SOHO satellite. The UVCS started to observe the extended corona at the end of January 1996; it routinely obtains coronal spectra in the 1145 A˚ - 1287 A˚, 984 A˚ - 1080 A˚ ranges, and intensity data in the visible continuum. Through…