Search Publications
Flare observation of the Sun as a star by SUMER/SOHO in the hydrogen Lyman continuum
Vial, J. -C.; Wilhelm, K.; Curdt, W. +3 more
During the execution of the programme ``Sun as a star'', while the SUMER (Solar Ultraviolet Emission of Emitted Radiation)/SOHO (SOlar and Heliospheric Observatory) slit was collecting the scattered radiation from the telescope mirror far away from the solar disk image, a class X5.3/3b flare erupted on the solar disk, on 25 August 2001. During the…
Temperature dependence of the Lyman α line wings in cool hydrogen-rich white dwarf atmospheres. Application to ZZ Ceti white dwarf spectra
Kielkopf, J. F.; Allard, N. F.; Loeillet, B.
Theoretical Lyman α absorption profiles show a significant dependence on temperature of the H2 satellite at 1600 Å, whereas the H2+ satellite at 1400 Å remains unchanged. The use of opacities calculated with different approximations concerning the electric dipole transition moment (constant, dependent on interatomi…
RX J1821.6+6827: A cool cluster at z = 0.81 from the ROSAT NEP survey
Böhringer, H.; Wolter, A.; Briel, U. G. +3 more
We present an analysis of the properties of the cluster of galaxies RX J1821.6+6827, or NEP 5281, at a redshift z= 0.816 ±0.001. RX J1821.6+6827 was discovered during the optical identification of the X-ray sources in the North Ecliptic Pole (NEP) region of the ROSAT All-Sky Survey and it is the highest redshift cluster of galaxies of the NEP surv…
Misleading results from low-resolution spectroscopy: From galaxy interstellar medium chemistry to cosmic star formation density
Flores, H.; Hammer, F.; Gruel, N. +2 more
Low resolution spectroscopy (R=150) from the Canada-France-Redshift Survey (CFRS) revealed intriguing properties for low redshift galaxies (z ≤0.3): nearly half of their spectra show prominent Hα emission lines, but no Hβ emission line and barely detected [O II] λ3727, and [O III] λ5007 lines. We call these objects ``CFRS Hα-single" galaxies and h…
X-ray variability of the Narrow Line Seyfert 1 Galaxy PKS 0558-504
Arévalo, P.; Brinkmann, W.; Gliozzi, M. +1 more
We present results from several XMM-Newton observations of the radio-loud Narrow-line Seyfert 1 galaxy (NLS1) PKS 0558-504. We find evidence for strong and persistent X-ray variability, both on short and long time-scales. On short time scales of ⪆2 hours the source varies smoothly by 15-20%; long-term variations by a factor ⪆2 could not be resolve…
Detection of Saturnian X-ray emission with XMM-Newton
Schmitt, J. H. M. M.; Ness, J. -U.; Robrade, J.
The giant planet Saturn was observed by XMM-Newton in September 2002. We present and analyse these XMM-Newton observations and compare our findings to the Chandra observations of Saturn. Contamination of the XMM-Newton data by optical light is found to be severe in the medium and thin filters, but with the thick filter all optical light is suffici…
STIS observations of FLIERs in NGC 7662
Balick, B.; Corradi, R. L. M.; Patriarchi, P. +1 more
We observed the planetary nebula NGC 7662 with STIS on board the HST to investigate the physical conditions in the microstructures within the nebula at high spatial resolution and to closely examine the physical conditions in FLIERs. We aim to reveal spectroscopic differences in small scale structures moving at about the same velocity as the surro…
Dynamics of the fast solar tachocline. II. Migrating field
Forgács-Dajka, E.
We present detailed numerical calculations of the fast solar tachocline based on the assumption that the dynamo field dominates over the dynamics of the tachocline. In the present paper of the series, we focus on three shortfalls of the earlier models. First, instead of the simple oscillating dipole poloidal field we study the more general magneti…
The field surrounding NGC 7603: Cosmological or non-cosmological redshifts?
López-Corredoira, M.; Gutiérrez, C. M.
We present new observations of the field surrounding the Seyfert galaxy NGC 7603, where four galaxies with different redshifts - NGC 7603 (z=0.029), NGC 7603B (z=0.057) and two fainter emission line galaxies (z=0.245 and z=0.394) - are apparently connected by a narrow filament, leading to a possible case of anomalous redshift. The observations com…
Properties and nature of Be stars Dra. XXIII. Long-term variations and physical properties of κ Dra.
Harmanec, P.; Hadrava, P.; Krtička, J. +9 more
We present an analysis of new spectroscopic observations of the bright Be star