Search Publications

Lyα/Hα Ratio of Singly Ionized Helium in Quasars

Zheng, Wei; Fang, Li-Zhi

He II Lyα λ304/Hα λ1640 emission lines are mainly produced by recombination, and their canonical ratio of ~10 may be a sensitive reddening indicator. We obtain the high signal-to-noise ratio optical spectra of two quasars and combine them with the far-ultraviolet spectra that show the He II λ304 emission. For HS 1700+64, the He II λ1640 emission i…

The Intermittently Embedded Herbig Ae/Be Stars ISO and Ground-Based IR Observations

Sitko, M. L.; Grady, C. A.; Grinin, V. P. +7 more

We discuss silicate emission profiles observed with the ISO SWS and ground-based IR observations in a population of intermittently embedded Herbig Ae/Be stars which are viewed edge-on to their polarimetrically identified dust and gas disks. The ISO SWS observations confirm the lack of a simple correlation between system age and the profile shape. …

Wave power dropouts associated with radial field intervals in high speed solar wind

Balogh, A.; McComas, D. J.; Horbury, T. S. +1 more

Examination of 770 days of heliospheric magnetic field data recorded within polar solar wind by the Ulysses spacecraft revealed a number of occasions when the wave power decreased by more than an order of magnitude for several hours. These power dropouts were found to be associated with intervals when the magnetic field was closely aligned with th…

Episodic Mass Loss and Rapid Lithium Enrichment and Depletion in K Giants

de La Reza, R.; Drake, N. A.; da Silva, L.

ISOPHOT S Observations of 3 M Dwarfs

Liebert, James; Leinert, Christoph; Wehrse, Rainer +2 more

The M dwarfs GL 832 (spectral type M2), GL 887 (M1), and GL 1 (M2) have been observed with the ISOPHOT spectrophotometers in the range 2.5-12µm at high signal-to-noise ratios. Since optical and ground based near-infrared data are also available, more than 95 % of the total flux is now covered for these objects. It is seen that between 2.5 µm and a…

Visualization of three-dimensional datasets

Walsh, Robert W.; Ireland, Jack; Galsgaard, Klaus

The effective visualization of three-dimensional (3d) datasets, both observationally and computationally derived, is an increasing problem in solar physics. We present here plots of computational data derived from the 3d reconstruction of the magnetic field of a loop system, rendered as anaglyphs. By combining images of the same 3d object from two…

Numerical Modelling and Simulation for Multi-Spacecraft Data Analysis: Approaches and Examples

Büchner, Jörg; Kuska, Jens-Peer; Wiechen, Heinz

CP stars: Photometric calibrations of luminosity using HIPPARCOS data

Jordi, C.; Luri, X.; Figueras, F. +7 more

The application of the Stromgren photometric luminosity calibrations to different types of CP stars is reexamined in the light of the new Hipparcos data. A first attempt is made to use the LM statistical parallax method - based on the maximum likelihood principle - to obtain a calibration of the absolute magnitude as a function of two Stromgren co…

Hubble Space Telescope-WFPC2/Hα Observations of the Ejected Nebula M1-67

Moffat, Anthony F. J.; Grosdidier, Yves; Acker, Agnès

We present HST-WFPC2/Hα deep images of the ejected nebula M1-67. Our data suggest that M1-67 is the imprint of a previous, slow LBV wind ejected from the central star WR124, now a WN8 star. We find evidence that the LBV wind is highly variableand anisotropic. Some dense, persisting clumps have possibly been ejected directly from the stellar surfac…

Planetary Nebulae

Cox, P.

This review summarizes spectroscopic and imaging results obtained on board the Infrared Space Observatory (ISO) on well-known planetary nebulae: the young nebula NGC 7027, and two fully evolved nearby nebulae, the Dumbbell and the Helix.