Search Publications
The Case against Cold, Dark Chromospheres
Kalkofen, Wolfgang
Is the solar chromosphere always hot, with relatively small temperature variations (δT/T~0.1), or is it cold most of the time, with temperature fluctuations that reach δT/T~10 at the top of the chromosphere? Or, equivalently, is the chromosphere heated continually or only for a few seconds once every 3 minutes? Two types of empirical model, one es…
Ultraviolet Coronagraph Spectrometer Observations of a High-Latitude Coronal Hole with High Oxygen Temperatures and the Next Solar Cycle Polarity
Cranmer, S. R.; Kohl, J. L.; Miralles, M. P.
We announce the resurgence of extreme ion properties in a large, high-latitude coronal hole observed above the north heliographic pole in 2001 February at solar maximum. The observations were taken with the Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric Observatory. These observations are part of an ongoing campaign to determin…
Dynamical mass determination for the very low mass stars LHS 1070 B and C
Mazeh, T.; Zucker, S.; Leinert, Ch. +4 more
We followed the relative orbit of the close pair of very late-type stars in the nearby triple system LHS 1070 during the past seven years. These observations are used to derive the astrometric elements of the orbit. Using the period of 16.1 +/- 1.4 years and assuming the distance of 7.39 pc given by van Altena (\cite{vanaltena95}) to be exactly co…
Multi-spacecraft observations of broadband waves near the lower hybrid frequency at the Earthward edge of the magnetopause
Balogh, A.; Wahlund, J. -E.; Lucek, E. +18 more
Broadband waves around the lower hybrid frequency (around 10 Hz) near the magnetopause are studied, using the four Cluster satellites. These waves are common at the Earthward edge of the boundary layer, consistent with earlier observations, and can have amplitudes at least up to 5 mV/m. These waves are similar on all four Cluster satellites, i.e. …
Spatially Resolved STIS Spectra of WR+OB Binaries with Colliding Winds
Moffat, Anthony F. J.; Lépine, Sébastien; Shara, Michael M. +2 more
We present spatially resolved spectra of the visual WR+OB massive binaries WR 86, WR 146, and WR 147, obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. The systems are classified as follows: WR 86=WC 7+B0 III, WR 146=WC 6+O8 I-IIf, WR 147=WN 8+O5-7 I-II(f). Both WR 146 and WR 147 are known to have strong n…
CME-Driven Solar Wind Disturbances at High Heliographic Latitudes
Forsyth, R. J.; Gosling, J. T.
We have identified 20 coronal mass ejections, or CMEs, in the solar wind in the Ulysses data obtained between S30° and S75° during the second polar orbit. Unlike CME-driven disturbances observed at high latitudes during Ulysses' first polar orbit, these disturbances had plasma and magnetic field characteristics similar to those observed in the ecl…
Sr II and [Sr II] Emission in the Ejecta of η Carinae
Gull, Theodore R.; Hartman, Henrik; Davidson, Kris +3 more
We have discovered four extremely surprising emission lines of strontium in ejecta near η Carinae. Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) observations made in 1999 show two narrow features whose wavelengths correspond to the forbidden transitions of Sr II, and we have found no other plausible identification for th…
A G1-like Globular Cluster in NGC 1023
Larsen, Søren S.
The structure of a very bright (MV=-10.9) globular cluster in NGC 1023 is analyzed on two sets of images taken with the Hubble Space Telescope. From careful modeling of King profile fits to the cluster image, a core radius of rc=0.55+/-0.1 pc, effective radius Re=3.7+/-0.3 pc, and a central surface brightness of &m…
Millimeter-radio, SOHO/EIT 171 Å features and the polar faculae in the polar zones of the Sun
Urpo, S.; Valtaoja, E.; Riehokainen, A. +3 more
In this work we study different manifestations of activity in the polar zones of the Sun in order to gain understanding on the phenomenon of enhanced radio temperature regions (ETR) at high solar latitudes. We have obtained simultaneous radio and optical data during 9 days in 1997. The radio data from the Metsähovi radio telescope, Finland, consis…
Hipparcos Trigonometric Parallaxes and the Distance Scale for Open Star Clusters
Beshenov, G. V.; Loktin, A. V.
Hipparcos trigonometric parallaxes are used to estimate the distances to the maximum possible number of open star clusters (OSC); distance moduli are estimated for 45 clusters with maximum heliocentric distances of about 1000 pc. The latter value can serve as an estimate of the limit to which it still makes sense to use Hipparcos trigonometric par…