Search Publications

Intercalibration of SUMER and CDS on SOHO. I. SUMER detector A and CDS NIS

Solanki, Sami K.; Schühle, Udo; Hollandt, Jörg +6 more

Predicted HST FOC and broad band colours for young and intermediate simple stellar populations.

Romaniello, M.; Castellani, V.; Brocato, E. +1 more

This paper presents theoretical HST and broad band colours from population synthesis models based on an homogeneous set of stellar evolutionary tracks as computed under canonical (no overshooting) assumptions, covering the range of cluster ages from t = 8 Myr to t = 5 Gyr for three different metallicities (Z=0.02, 0.006, and 0.001). Statistical fl…

The Ionizing Star Clusters of Giant H II Regions in NGC 2403

Drissen, Laurent; Moffat, Anthony F. J.; Shara, Michael M. +1 more

We present the results of a study on the massive star population down to about M_V~-3.1, or 12-15 M_solar, of the most luminous giant H II regions in the nearby spiral galaxy NGC 2403, based on Hubble Space Telescope images and ground-based spectrograms. Particular emphasis is placed on the distribution of the Wolf-Rayet and red supergiant stars a…

[Cii] 158-µm observations of a sample of late-type galaxies from the Virgo cluster

Metcalfe, L.; Völk, H. J.; Heinrichsen, I. +6 more

We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESA's Infrared Space Observatory (ISO) obtaining spectra around the [Cii] 157.741-µm fine-structure line. These 19 galaxies are quiescent in star-forming activity compared with previous studies from airborne observatories, sample RC3 types 0…

Hubble Space Telescope Observations of the Nucleus of Comet 45P/Honda-Mrkos-Pajdusakova and Its Inner Coma

Lamy, P. L.; A'Hearn, M. F.; Toth, I. +1 more

The nucleus of Comet 45P/Honda-Mrkos-Pajdusakova was detected during Hubble Space Telescope observations taken with the Wide-Field Planetary Camera 2 (WFPC2) in February 1996 when the comet was 0.17 AU from the Earth. The high spatial resolution (1 pixel projected to 5.6 km at the distance of the comet) allowed us to separate the signal of the nuc…

Source of Solar Acoustic Modes

Kosovichev, A. G.; Nigam, R.

Solar acoustic modes are found to be excited in a thin superadiabatic layer of turbulent convection (about 75+/-50 km below the photosphere) beneath the Sun's surface. Comparing the theoretical power spectra of both velocity and pressure oscillations of medium angular degree with that obtained from the Michelson Doppler Imager instrument on board …

The Chromosphere in Coronal Holes and the Quiet-Sun Network: an HE I (584 Å) Full-Disk Scan by SUMER/SOHO

Peter, H.

A raster scan by Solar Ultraviolet Measurements of Emitted Radiation/Solar and Heliospheric Observatory (SOHO) of the full solar disk containing over 2 million individual spectra of the He I line at 584 Å provides the possibility to study small- and large-scale variations of intensity, line shift, and line width. New striking features are the enha…

Origin, Injection, and Acceleration of CIR Particles: Observations Report of Working Group 6

Fränz, M.; Simnett, G. M.; Klecker, B. +18 more

This report emphasizes new observational aspects of CIR ions revealed by advanced instruments launched on the Ulysses, WIND, SOHO, and ACE spacecraft, and by the unique vantage point of Ulysses which carried out the first survey of Corotating Interaction Region (CIR) properties over a very wide range of heliolatitudes. With this more complete obse…

A simultaneous maximum likelihood approach for galaxy-galaxy lensing and cluster lens reconstruction

Schneider, Peter; Geiger, Bernhard

In a previous paper we investigated means for constraining the mass distribution of cluster galaxies by weak lensing. We concluded that a comprehensive method should treat the lensing effects of individual cluster galaxies and those resulting from a general cluster component simultaneously. To this end we now develop a non-parametric maximum likel…

Hubble Space Telescope WFPC2 Imaging of XZ Tauri:Time Evolution of a Herbig-Haro Bow Shock

Ballester, Gilda E.; Krist, John E.; Crisp, David +13 more

We report observations of dramatic morphological changes in the extremely young Herbig-Haro object ejected by the pre-main-sequence binary XZ Tauri. Hubble Space Telescope images taken in 1995 showed a filled bubble of emission nebulosity extending 4" north-northeast of the system in the direction of a previously known jet. New images obtained in …