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HR 1817: the EUV properties of an active F dwarf
Mullan, D. J.; Mathioudakis, M.
We examine the coronal properties of the active F dwarf HR 1817. Photometric observations with EUVE show that the source is in a near-continuous state of flare-like activity. Using IUE and EUVE spectroscopic observations we construct the emission measure distribution in the 10(4) -10(7.2) K temperature range. These observations reveal a hot corona…
OH lines in the FIR spectra of the OH megamaser galaxies IRAS 20100-4156 and 3Zw35
Quirrenbach, A.; Kegel, W. H.; Hertenstein, T.
Using the SWS and LWS instruments on board of the ISO spacecraft, we searched for OH-lines in the FIR spectra of the two OH megamaser galaxies IRAS 20100-4156 and 3 Zw 35. The lines at 34 mu and 53 mu were detected in absorption with certainty in the spectrum of IRAS 20100-4156 and probably in the spectrum of 3 Zw 35. From the measured equivalent …
Can Streamer Blobs Prevent the Buildup of the Interplanetary Magnetic Field?
Martens, P. C. H.; van Aalst, M. K.; Beliën, A. J. C.
Coronal mass ejections continuously drag closed magnetic field lines away from the Sun, adding new flux to the interplanetary magnetic field (IMF). We propose that the outward-moving blobs that have been observed in helmet streamers are evidence of ongoing, small-scale reconnection in streamer current sheets, which may play an important role in th…
Parameters of four multiple systems from speckle interferometry
Hofmann, K. -H.; Tokovinin, A. A.; Balega, Yu. Yu. +2 more
New or refined visual orbital elements are presented for four double stars (HR 266 AP, 88 Tau AP = CHARA 18, eta Ori AB = McA18, ADS 16904 AP = CHARA 149) that are members of multiple systems. Relative photometry and positional speckle measurements with the 6-m telescope and published radial-velocity data for the stars are used. Photometric data a…
Variable central stars of young Planetary Nebulae. A photometric study of the central star of M 2-54
Handler, G.
We acquired 63.8 hours of time-series photometry of the variable central star of the young Planetary Nebula M 2-54. This object exhibits light variations with a peak-to-peak amplitude of up to 0.3 mag in Johnson V. Two different time scales (several days and several hours) are present. While the long-term variations appear to be nonperiodic, the s…
Dust extinction and intrinsic SEDs of carbon-rich stars. III. The Miras, CS, and SC stars
Bergeat, J.; Knapik, A.; Rutily, B.
The present work is an extension of a recent study by Knapik & Bergeat (\cite{knapik97}), and Bergeat et al. (\cite{berge98b}) henceforth called Papers I and II, respectively. The spectral energy distributions (SEDs) of about 440 carbon-rich stars and the interstellar extinction observed on their line of sights were analysed. The methods origi…
Interstellar reddening from the HIPPARCOS and TYCHO catalogues. II. Nearby dust features at the NGP associated with approaching HI gas
Knude, J.; Høg, E.
The Hipparcos and Tycho Catalogues offer an interesting possibility to study the local distribution of the interstellar reddening from the combination of data contained in the catalogues: Hipparcos parallaxes, Tycho B - V and spectral and luminosity classification compiled from the literature, mainly the Michigan Catalogs. In some cases the distan…
Radio-optical alignments in a low radio luminosity sample
Rawlings, Steve; Lacy, Mark; Ridgway, Susan E. +2 more
We present an optically based study of the alignment between the radio axes and the optical major axes of eight z~0.7 radio galaxies in a 7C sample. The radio galaxies in this sample are ~20 times less radio-luminous than 3C galaxies at the same redshift, and are significantly less radio-luminous than any other well-defined samples studied to date…
Adaptive optics observations of luminous infrared galaxies. II. Imaging of the merging galaxy Arp 299
Rouan, D.; Doyon, R.; Rigaut, F. +2 more
We present adaptive optics observations of the Luminous Infrared Galaxy, Arp 299. This merging galaxy (NGC 3690) is the site of a very powerful starburst activity. Very high angular resolution observations at 2.2mic reveal many super-clusters of newly formed stars. Those clusters feature intrinsic luminosities and surface densities well above the …
Analyzing the Energetics of Explosive Events Observed by SUMER on SOHO
Winebarger, Amy R.; Warren, Harry P.; Mariska, John T. +1 more
The SUMER spectrometer on SOHO has obtained numerous observations of optically thin chromosphere-corona transition-region line profiles with high spatial, spectral, and temporal resolution. Many of these profiles exhibit asymmetries and broadenings associated with impulsive mass motions (explosive events) in the solar atmosphere. We present here a…