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Model Atmospheres with Individualized Abundances
Piskunov, N.; Kupka, F.
We describe a new method for computing opacity distribution functions (ODFs) for model atmosphere calculations. The method is tailored to model the atmospheres of individual stars on a modern workstation. Our goal is the computation of model atmospheres for stars with abundances significantly different from the solar or scaled solar composition ty…
XMM-Newton survey of the low-metallicity open cluster NGC 2516
Gondoin, P.; Read, A. M.; Grosso, N. +8 more
We present the first results of an XMM-Newton EPIC survey of NGC 2516, a southern low-metallicity open cluster with an age close to the Pleiades. The attained limiting sensitivity is of ~ 2.4 10-15 erg s-1 cm-2 in the 0.1-4.0 keV bandpass. This has been achieved by summing the data of the MOS and PN cameras of two …
System parameters of the long-period polar V1309 Ori
Schwope, A. D.; Schwarz, R.; Staude, A.
Based on high-resolution optical spectroscopy in the blue and the near infra-red spectral range, we derived velocity images (Doppler tomograms) of the mass-donating secondary star and the accretion stream of the long-period eclipsing polar V1309 Ori (RX J0515.41+0104.6). Combined with HST-spectroscopy of high time resolution and optical photometry…
4U 2206+54: An Unusual High-Mass X-Ray Binary with a 9.6 Day Orbital Period But No Strong Pulsations
Corbet, Robin H. D.; Peele, Andrew G.
Rossi X-Ray Timing Explorer (RXTE) All-Sky Monitor observations of the X-ray source 4U 2206+54, previously proposed to be a Be star system, show the X-ray flux to be modulated with a period of approximately 9.6 days. If the modulation is due to orbital variability, then this would be one of the shortest orbital periods known for a Be star X-ray so…
Results from UVCS and LASCO Observation of the Sungrazing Comet C/2000 C6
Raymond, J. C.; Wu, R.; Uzzo, M. +4 more
During 2000 February 9-10, the Large Angle Spectrometric Coronagraph and Ultraviolet Coronal Spectrometer (UVCS) instruments aboard the Solar and Heliospheric Observatory observed comet C/2000 C6, a member of the Kreutz family of sungrazing comets. A tail nearly 0.5 Rsolar in length was detected in Lyα emission. UVCS was able to observe…
Origin of the Solar Wind: Theory
Schwadron, N. A.; Fisk, L. A.
A theory is presented for the origin of the solar wind, which is based on the behavior of the magnetic field of the Sun. The magnetic field of the Sun can be considered as having two distinct components: Open magnetic flux in which the field lines remain attached to the Sun and are dragged outward into the heliosphere with the solar wind. Closed m…
On the Unresolved Fine Structures of the Solar Upper Atmosphere. IV. The Interface with the Chromosphere
Wilhelm, K.; Dammasch, I. E.; Feldman, U.
An important objective of the solar physics community is the unambiguous determination of the morphology of the fine structures of the solar upper atmosphere in quiet-Sun and coronal hole regions and the relationship of the cold chromosphere to the hot corona. Recently the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on board t…
Hα Imaging with Hubble Space Telescope-NICMOS of an Elusive Damped Lyα Cloud at z=0.6
Charlton, Jane C.; Bouché, Nicolas; Bershady, Matthew A. +3 more
Despite previous intensive ground-based imaging and spectroscopic campaigns and wideband Hubble Space Telescope (HST) imaging of the z=0.927 QSO 3C 336 field, the galaxy that hosts the damped Lyα system along this line of sight has eluded detection. We present a deep narrowband Hα image of the field of this zabs=0.656 damped Lyα absorbe…
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…