Search Publications
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
The stellar content, metallicity and ionization structure of H II regions
Tielens, A. G. G. M.; Peeters, E.; van der Hulst, J. M. +2 more
Observations of infrared fine-structure lines provide direct information on the metallicity and ionization structure of H Ii regions and indirectly on the hardness of the radiation field ionizing these nebulae. We have analyzed a sample of Galactic and Magellanic Cloud H Ii regions observed by the Infrared Space Observatory (ISO) to examine the in…
A rapidly variable narrow X-ray iron line in Mkn 841
Maraschi, L.; Henri, G.; Matt, G. +8 more
We report on the detection of a rapidly variable narrow Fe Kalpha line in Mkn 841. The source has been observed two times by XMM-Newton and simultaneously with BeppoSAX. The two observations, of about 10 ks long each, were separated by ~ 15 hours. The line flux reaches a maximum during the first observation and is significantly reduced in the seco…
CO and H2O vibrational emission toward Orion Peak 1 and Peak 2
van Dishoeck, E. F.; Cernicharo, J.; González-Alfonso, E. +3 more
ISO/SWS observations of Orion Peak 1 and Peak 2 show strong emission in the ro-vibrational lines of CO v=1-0 at 4.45-4.95 µm and of H2O ν2=1-0 at 6.3-7.0 µm. Toward Peak 1 the total flux in both bands is, assuming isotropic emission, ≈2.4 and ≈0.53 Lsun, respectively. This corresponds to ≈14 and ≈3% of …
Iron abundance in hot hydrogen-deficient central stars and white dwarfs from FUSE, HST, and IUE spectroscopy
Rauch, T.; Werner, K.; Kruk, J. W. +3 more
We present a first systematic investigation of the iron abundance in very hot (Teff >= 50 000 K) hydrogen-deficient post-AGB stars. Our sample comprises 16 PG 1159 stars and four DO white dwarfs. We use recent FUSE observations as well as HST and IUE archival data to perform spectral analyses with line blanketed NLTE model atmosphere…