Search Publications
A 25 micron search for Vega-like disks around main-sequence stars with ISO
Kessler, M. F.; Siebenmorgen, R.; Dominik, C. +5 more
We present an ISO 25 mu m photometric survey of a sample of 81 nearby main-sequence stars in order to determine the incidence of ``warm'' dust disks. All stars were detected by ISO. We used an empirical relation to estimate the photospheric flux of the stars at 25 mu m. We find 5 stars (6%) with excess above the photospheric flux which we attribut…
The role of magnetic bald patches in surges and arch filament systems
Mandrini, C. H.; Schmieder, B.; Démoulin, P. +2 more
The short-lived active region (AR) NOAA 7968 was thoroughly observed all along its disk transit (June 3 to 10, 1996) from space and from the ground. During the early stage of its evolution, flux emerged in between the two main polarities and arch filament systems (AFS) were observed to be linked to this emergence. New bipoles and a related surge w…
X-ray sources in the starburst spiral galaxy M 83. Nuclear region and discrete source population
Soria, R.; Wu, K.
Chandra has resolved the starburst nuclear region of the face-on grand-design spiral M 83. Eighty-one point sources are detected (above 3.5-sigma ) in the ACIS S3 image, and 15 of them are within the inner 16\arcsec region of the galaxy. A point source with Lx ~ 3 x 1038 erg s-1 in the 0.3-8.0 keV band is found to …
Simultaneous X-ray spectroscopy of YY Gem with Chandra and XMM-Newton
Schmitt, J. H. M. M.; Burwitz, V.; Neuhäuser, R. +7 more
We report on a detailed study of the X-ray spectrum of the nearby eclipsing spectroscopic binary YY Gem. Observations were obtained simultaneously with both large X-ray observatories, XMM-Newton and Chandra. We compare the high-resolution spectra acquired with the Reflection Grating Spectrometer onboard XMM-Newton and with the Low Energy Transmiss…
Conversion of relativistic pair energy into radiation in the jets of active galactic nuclei
Vainio, R.; Schlickeiser, R.; Pohl, M. +3 more
It is generally accepted that relativistic jet outflows power the nonthermal emission from active galactic nuclei (AGN). The composition of these jets - leptonic versus hadronic - is still under debate. We investigate the microphysical details of the conversion process of the kinetic energy in collimated relativistic pair outflows into radiation t…
Ionized iron Kalpha lines in AGN X-ray spectra
Bianchi, S.; Matt, G.
The Equivalent Widths (EW) of the He- and H-like iron lines produced in photoionized, circumnuclear matter of AGN are calculated with respect to both the reflected and the total continua. We found that the EWs with respect to the total continuum may be as large as a few tens of eV, making them observable in bright Seyfert 1s by instruments on boar…
RU Cen and SX Cen: Two strongly depleted RV Tauri stars in binary systems. The RV Tauri photometric b phenomenon and binarity
Maas, T.; Van Winckel, H.; Waelkens, C.
We present a chemical abundance analysis on the basis of high signal-to-noise and high-resolution (lambda /Delta lambda ~ 48 000) optical spectra of two RV Tauri stars RU Cen and SX Cen. With an [Fe/H] = -1.9 and a [Zn/Fe] = +0.9 for RU Cen and a [Fe/H] = -1.1 and a [Zn/Fe] = +0.6 for SX Cen, both stars of spectroscopic class B display strong depl…
The time variation in infrared water-vapour bands in Mira variables
Onaka, T.; Murakami, H.; Yamamura, I. +2 more
The time variation in the water-vapour bands in oxygen-rich Mira variables has been investigated using multi-epoch ISO/SWS spectra of four Mira variables in the 2.5-4.0 mu m region. All four stars show H2O bands in absorption around minimum in the visual light curve. At maximum, H2O emission features appear in the ~ 3.5-4.0 m…
The HST survey of the B2 sample of radio-galaxies: Optical nuclei and the FR I/BL Lac unified scheme
Capetti, A.; Morganti, R.; Chiaberge, M. +4 more
We examine the optical properties of the nuclei of low luminosity radio-galaxies using snapshot HST images of the B2 sample. In agreement with the results obtained from the analysis of the brighter 3C/FR I sample, we find a correlation between fluxes (and luminosities) of the optical and radio cores. This provides further support for the interpret…
X-ray and optical observations of 1RXS J154814.5-452845: A new intermediate polar with soft X-ray emission
Haberl, F.; Motch, C.; Zickgraf, F. -J.
We report the identification of the ROSAT all-sky survey source