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The Balmer Wavelength Range of BP Tauri
Ardila, David R.; Basri, Gibor
We have analyzed all the observations of BP Tauri taken by the International Ultraviolet Explorer (IUE) in the low-resolution (Δλ~6 Å), long-wavelength (λ=1850-3350 Å) range. This data set contains 61 spectra. We observe variability in the ultraviolet continuum of Δmcont.~1 mag and variability in the Mg II line flux of ΔmMgII…
CO2 emission in EP Aqr: Probing the extended atmosphere
Waters, L. B. F. M.; Justtanont, K.; Tielens, A. G. G. M. +3 more
We present an analysis of the ISO/SWS full resolution scan between 12.5 and 16.5 µm of the O-rich AGB star EP Aqr, exhibiting a number of strong CO2 emission bands. We have developed a simple LTE model to calculate theoretical CO2 spectra assuming a single-layer slab geometry and compared the SWS observations to this mo…
Pinpointing the Position of the Post-Asymptotic Giant Branch Star at the Core of RAFGL 2688 Using Polarimetric Imaging with NICMOS
Hines, Dean C.; Kastner, Joel H.; Sahai, Raghvendra +1 more
We have used infrared polarimetric imaging with NICMOS to determine precisely the position of the star that illuminates (and presumably generated) the bipolar, preplanetary reflection nebula RAFGL 2688 (the Egg Nebula). The polarimetric data pinpoint the illuminating star, which is not detected directly at wavelengths <=2 µm, at a positio…
Monitoring solar activity on the far side of the sun from sky reflected Lyman α radiation
Bertaux, Jean-Loup; Lallement, Rosine; Schmidt, Walter +3 more
Solar active regions are known to be brighter in Lyman α radiation than the quiet sun. Accordingly, they illuminate more H atoms in interplanetary space through resonance scattering. As we show here, this excess of illumination related to active regions is clearly seen in full-sky Lyman α maps recorded by the SWAN instrument on board SOHO, includi…
New insights into the narrow-line Seyfert 1 phenomenon
Mathur, Smita
I briefly review the X/UV absorber models and show that the observations of NLS1s are generally consistent with the models. The covering factor of absorbers in NLS1s is likely to be high and there is some evidence of super-solar metallicities. I argue that NLS1s may be active galaxies in the early stage of their evolution and as such, may be low l…
Emergence of a U-loop - sub-photospheric link between solar active regions
van Driel-Gesztelyi, L.; Démoulin, P.; Malherbe, J. -M.
Using SOHO/MDI magnetic maps we present the first direct observational evidence for the emergence of a U-loop in the solar photosphere. We show that two active regions (ARs), i.e. two adjacent Omega -loops, which were emerging at the same time at the same solar latitude, about 150000 km distance in longitude from each other, emerged from at least …
T Tauri stars: The UV/X-ray connection
Costa, V. M.; Lago, M. T. V. T.; Norci, L. +1 more
We have analysed newly calibrated IUE and ROSAT data for three T Tauri stars from different subclasses: TW Hya, V410 Tau and CS Cha, a Classical T Tauri star (CTTS), a Weak T Tauri star (WTTS) and a T Tauri star intermediate between CTTS and WTTS, respectively. In the ultraviolet the continuum seems to be well explained by the sum of the stellar b…
Context and heliographic dependence of heliospheric planar magnetic structures
Balogh, A.; Jones, G. H.
An analysis is presented of planar magnetic structures (PMSs) detected in the solar wind by the Ulysses spacecraft between its launch in October 1990 and the end of 1998. In all, 667 such structures were found, with durations between 6 hours (the minimum in the search algorithm) and 66 hours. The total amount of magnetometer data found to represen…
Sigmoid CME source regions at the Sun: some recent results
Sterling, A. C.
Identifying coronal mass ejection (CME) precursors in the solar corona would be an important step in space weather forecasting, as well as a vital key to understanding the physics of CMEs. Twisted magnetic field structures are suspected of being the source of at least some CMEs. These features can appear sigmoid (S or inverse-S) shaped in soft X-r…
ISOPHOT observations of 3CR quasars and radio galaxies
de Graauw, T.; Barthel, P. D.; van Bemmel, I. M.
In order to check for consistency with the radio-loud AGN unification scheme, ISOPHOT data obtained for two small sets of intermediate redshift steep-spectrum 3CR radio galaxies and quasars are being examined. Supplementary submillimeter and centimeter radio data for the quasars are also taken into account, in order to assess the magnitude of any …