Search Publications
Differential emission measure distributions of Capella and σ2 CrB
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
The active late-type stars Capella (α Aur G6III+F9III) and σ2 CrB (F6V+GV) (X-ray candidate emitters underlined) were observed with the EXOSAT Transmission Grating Spectrometer (TGS) in the region 10-200 Å. We have made an analysis of the differential emission measure (DEM) distribution. The derived DEM peaks between 3 and 7 MK and abov…
Possible effects of organelle charge and density on cell metabolism
Keenan, F. P.; Bates, B.; Catney, M. G.
To respond to gravity a biological system must: First, perceive the stimulus; and, second transduce the stimulus into an appropriate response. This laboratory has studied a system of perception and transduction involving the gravity-induced asymmetric distribution of a plant growth hormone. From these studies we have developed a working theory whi…
Magnetic reconnection and energy release in a long-duration stellar flare
Pallavicini, R.; Poletto, G.; Kopp, R. A.
A dynamical model of magnetic reconnection in solar two-ribbon flares is applied to EXOSAT observations of a long-decay flare from the star EQ Peg. We show that the model is able of reproducing correctly the energy release rate and temporal evolution of the decay phase of the observed flare. We conclude that the flare was the stellar counterpart o…
Distribution and kinematics of MgII in the LISM
Molaro, P.; Beckman, J. E.; Vladilo, G. +1 more
We have analyzed MgII emissions in the IUE spectra of 91 cool stars in a systematic search for interstellar components. 60% of the stars show evidence of interstellar contamination. The radial velocities of the IS features show that even at short distances (d < 30 pc) the motion of the LISM agrees with that derived from the analysis of optical …
Evolution of the chromospheric and coronal activity of intermediate mass stars
Brown, Alexander
Recent ultraviolet and X-ray observations pertaining to the outer atmospheric structure of intermediate mass (4-6 M0) stars and the evolution of their structure are presented. A distance-limited (d <= 200 pc) IUE ultraviolet survey of early K bright giants shows that C IV emission commonly is present. These stars are almost evenly sp…
Ultraviolet interstellar lines towards nearby fast rotators: ZnII distribution and MgII/MgI ratios
Molaro, P.; Beckman, J. E.; Centurion, M. +1 more
We present the column density distribution of the LISM towards a sample of 15 fast rotators observed with IUE at high resolution. The targets are closer than 200 pc and most of them have lines of sight not previously investigated. Hydrogen column densities are inferred using zinc, known to be little depleted. The results are in general agreement w…
Giotto observations of the bow shock at Comet Halley
Winningham, J. D.; Thomsen, M.; Borg, H. +8 more
Preliminary results from the JPA instrument on Giotto indicate that Comet Halley, even on the flanks, has a bow shock which moves backwards and forwards over the spacecraft. To understand the structure properly will require more detailed investigation of the relationships between three particle populations, cometary ions, solar wind ions and elect…
A rapid planetary phase observed on the IUE spectral region of the carbon star, HD 59643
Querci, M.; Querci, F.; Johnson, H. R. +1 more
The IUE satellite has been used to obtain low-and high resolution LWP and SWP spectra of the unusual cool carbon star HD 59643 (R9; C6,2), which appears to suffer a planetary nebula phase. These spectra enable us to understand the nature of this fascinating object, which may be in a stage of rapid evolution. High resolution line profiles are exami…
EXOSAT observations of two gamma-ray burst sources
Hurley, K.; Motch, C.; Boer, M. +18 more
EXOSAT observations of the 19 Nov 1978 and 25 Mar 1979b gamma bursters are presented, for the 0.02-2.5 keV energy range. No source was detected in either case, leading to temperature upper limits for the neutron stars assumed to be present of 105-106 °K. Polar cap accretion rates are constrained to values of 10-12-…
Lyman-alpha emission from low dispersion IUE spectra
Catalano, S.; Bruno, M.; Marilli, E.
In spite of its importance as cooling mechanism of the chromosphere of late type stars, the hydrogen Lyman-alpha line has been neglected in most IUE programmes The high geocoronal background and the saturation often seen in the stellar emission peak are the major problems that prevent accurate determination of the Lyman alpha flux.
We have de…