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Characteristics of solar coronal streamers. Element abundance, temperature and density from coordinated CDS and UVCS SOHO observations
Bromage, G. E.; Parenti, S.; Raymond, J. C. +3 more
This paper presents the results from coordinated observations of streamers acquired by the SOHO Coronal Diagnostic Spectrometer (CDS) and UltraViolet Coronograph Spectrometer (UVCS) experiments. Data from different altitudes within the solar corona were taken, with the purpose of determining their physical parameters - densities, electron temperat…
Absorption spectra of Mg-rich Mg-Fe and Ca pyroxenes in the mid- and far-infrared regions
Koike, C.; Tsuchiyama, A.; Shibai, H. +6 more
Absorption spectra of the pyroxene group have been measured in mid and far infrared wavelengths. The samples are crystalline pyroxenes (enstatite, diopside, and natural pyroxene) and amorphous pyroxenes (enstatite and diopside glass). Especially, the synthetic pyroxenes such as orthoenstatite, clinoenstatite and diopside are pure and high-quality …
New PAH mode at 16.4 mu m
Schmidt, W.; Léger, A.; Moutou, C. +2 more
The detection of a new 16.4 mu m emission feature in the ISO-SWS spectra of NGC 7023, M17, and the Orion Bar is reported. Previous laboratory experiments measured a mode near this wavelength in spectra of PAHs (Polycyclic Aromatic Hydrocarbons), and so we suggest the new interstellar 16.4 mu m feature could be assigned to low-frequency vibrations …
The first VLT FORS1 spectra of Lyman-break candidates in the HDF-S and AXAF Deep Field
Aragón-Salamanca, A.; Cristiani, S.; Arnouts, S. +9 more
We report on low-resolution multi-object spectroscopy of 30 faint targets (R =~ 24-25) in the HDF-S and AXAF deep field obtained with the VLT Focal Reducer/low dispersion Spectrograph (FORS1). Eight high-redshift galaxies with 2.75< z < 4 have been identified. The spectroscopic redshifts are in good agreement with the photometric ones with a…
Multi-component structure of solar and stellar transition regions
Peter, H.
Emission lines from the solar transition region between the chromosphere and the corona often show a two Gaussian component profile with a core and a broad second component contributing up to 25% to the total intensity. For the first time a systematic study of the broadening and Doppler shift of the second weaker components is performed using SUME…
ISO spectroscopy of circumstellar dust in the Herbig Ae systems AB Aur and HD 163296
Waters, L. B. F. M.; van Dishoeck, E. F.; van den Ancker, M. E. +3 more
Using both the Short- and Long-wavelength Spectrometers on board the Infrared Space Observatory (ISO), we have obtained infrared spectra of the Herbig Ae systems AB Aur and HD 163296. In addition, we obtained ground-based N band images of HD 163296. Our results can be summarized as follows: (1) The main dust components in AB Aur are amorphous sili…
The γ Velorum binary system. II. WR stellar parameters and the photon loss mechanism
Schmutz, W.; Hillier, D. J.; Crowther, P. A. +4 more
In this paper we derive stellar parameters for the Wolf-Rayet star in the gamma Velorum binary system (WR11), from a detailed non-LTE model of its optical and infrared spectra. Compared to the study of Schaerer et al., the parameters of the WC8 star are revised to a hotter effective temperature (T_eff ~ 57 kK), a higher luminosity (log (L/Lsu…
Far infrared mapping of the gas cooling along the L1448 outflow
Codella, C.; Benedettini, M.; Lorenzetti, D. +4 more
The molecular outflows associated with the two Class 0 sources L1448-mm and L1448-IRS3 have been mapped with the spectrometers on board the ISO satellite allowing to study in detail the physical and chemical structure of the shocked gas. The far infrared cooling is mainly due to the emission from pure rotational lines of CO, H2O and H
Multi-colour PL-relations of Cepheids in the bt HIPPARCOS catalogue and the distance to the LMC
Groenewegen, M. A. T.; Oudmaijer, R. D.
We analyse a sample of 236 Cepheids from the hipparcos catalog, using the method of ``reduced parallaxes'' in V, I, K and the reddening-free ``Wesenheit-index''. We compare our sample to those considered by Feast & Catchpole (1997) and Lanoix et al. (1999), and argue that our sample is the most carefully selected one with respect to completene…
Non-LTE analysis of neutral magnesium in cool stars
Zhao, G.; Gehren, T.
Calculations of the statistical equilibrium of magnesium in the solar photosphere have shown that NLTE populations hardly affect Mg line formation in the Sun. However, in metal-poor dwarfs and giants the influence of electron collisions is reduced, and the ultraviolet radiation field, enhanced due to reduced background line opacity, results in mor…