Search Publications
On temperature and abundance effects during an X-ray flare on σ Geminorum
Nordon, R.; Güdel, M.; Behar, E.
We compare quiescent and flare X-ray spectra of the RS CVn binary σ Gem obtained with the Chandra and XMM-Newton grating spectrometers. We find that in addition to an overall 25% flux increase, which can be ascribed to variations in the system's quiescence activity over the 15 months that passed between the observations, there is a hot plasma comp…
Variations of the He II λ1640 line in B0e-B2.5e stars
Smith, M. A.
Using the International Ultraviolet Explorer data archive, we have examined the SWP echellograms of 74 B0-B2.5e stars for statistically significant fluctuations in the He II ("Hα") λ1640 line profile. In this sample we found that the He II line is occasionally variable in 10 stars over short to long timescales. The He II-variable stars discovered …
Curvelet analysis of asteroseismic data. I. Method description and application to simulated sun-like stars
García, R. A.; Starck, J. -L.; Pires, S. +3 more
Context: .The detection and identification of oscillation modes (in terms of their ℓ, m, and successive n) is a great challenge for present and future asteroseismic space missions. "Peak tagging" is an important step in the analysis of these data to provide estimations of stellar oscillation mode parameters, i.e., frequencies, rotation rates, and …
XMM-Newton survey of two upper Scorpius regions
Micela, G.; Peres, G.; Favata, F. +4 more
Aims.We studied X-ray emission from young stars by analyzing the deep XMM-Newton observations of two regions of the Upper Scorpius association with an age of 5 Myr.
Methods: .Based on near infrared and optical photometry we identified 22 Upper Scorpius photometric members among the 224 detected X-ray sources. We derived coronal properties of U…
ESO imaging survey: optical follow-up of 12 selected XMM-Newton fields
Motch, C.; Zaggia, S.; Watson, M. G. +12 more
This paper presents the data recently released for the XMM-Newton/WFI survey carried out as part of the ESO Imaging Survey (EIS) project. The aim of this survey is to provide optical imaging follow-up data in BVRI for identification of serendipitously detected X-ray sources in selected XMM-Newton fields. In this paper, fully calibrated individual …
Line formation regions of the UV spectrum of C I Cygni
Friedjung, M.; Mikołajewska, J.; Quiroga, C.
Aims.They are the interpretation of the emission line formation regions in
Methods: .They involve the examination of radial velocities and fluxes of ultraviolet emission lines at different epochs, deduced from archival IUE and GRHS/HST spectra.
Results: .The line fluxes give electron densities and were in additi…
Shock excitation of the knots of Hen 3-1475
Binette, L.; Raga, A. C.; Riera, A.
We present new optical STIS HST spectroscopic observations of the jets of the proto-planetary nebula Hen3-1475. The excitation conditions of the knots of Hen3-1475
are derived from the observed optical spectra, confirming that the knots are shock excited. The shocked spectra are qualitatively reproduced by simple "3/2"Dbow shock models. …The extragalactic Cepheid bias: a new test using the period-luminosity-color relation
Paturel, G.; Teerikorpi, P.
We use the Period-Luminosity-Color relation (PLC) for Cepheids to test for the existence of a bias in extragalactic distances derived from the classical Period-Luminosity (PL) relation. We calculate the parameters of the PLC using several galaxies observed with the Hubble Space Telescope and show that this calculation must be conducted with a PLC …
High resolution optical spectroscopy of IRAS 09425-6040 (=GLMP 260)
García-Lario, P.; García-Hernández, D. A.; Abia, C. +1 more
We present high resolution optical spectroscopic observations of IRAS 09425-6040, a peculiar, extremely red, C-rich AGB star showing prominent O-rich dust features in its ISO infrared spectrum attributed to crystalline silicates. Our analysis shows that IRAS 09425-6040 is indeed a C-rich star slightly enriched in lithium ({log (Li/H) + 12} ∼ 0.7) …
A new luminous supersoft X-ray source in NGC 300
Schirmer, M.; Wilms, J.; Kendziorra, E. +1 more
Context: .We report the discovery of a new luminous supersoft source,