Search Publications
Low-frequency p- and g-mode solar oscillations
Provost, J.; Berthomieu, G.; Morel, P.
In order to help the detection and identification of low-frequency p- and g-modes in the solar spectrum observed by ground-based networks and SoHO experiments, we study the properties of low degree (l=0 - 6) low-frequency (100 - 2000 mu Hz) solar oscillations. The frequencies of p- and g-modes have been computed for a set of solar models with upda…
ISO Spectroscopy of the young bipolar nebulae S106 IR and Cep A East
Tielens, A. G. G. M.; van den Ancker, M. E.; Wesselius, P. R.
We present the results of ISO SWS and LWS grating scans towards the embedded Young Stellar Objects (YSOs) S106 IR and Cep A East. Emission from the pure rotational lines of H_2 and the infrared fine structure lines of [C ii], [O i], [S i], [Si ii] and [Fe ii], as well as absorption bands due to H_2O, CO and CO_2 ice were detected toward Cep A. In …
Multiwavelength observations of N 66 in the SMC: unveiling photodissociation interfaces and star formation
Boulanger, F.; Contursi, A.; Maoli, R. +5 more
We present new observations of the major star-forming region N 66 in the Small Magellanic Cloud and of its surroundings, which add to those presented in Contursi et al. (\cite{Contursi99}, Paper I). High-sensitivity CO observations allowed the detection of molecular gas associated with the H i I region, for which a high-resolution image in [O iii …
Evaluation of solar energetic Fe charge states: effect of proton-impact ionization
Torsti, J.; Kocharov, L.; Kovaltsov, G. A. +1 more
We present the energy-dependent rates of ionization and recombination of energetic Fe ions in solar coronal plasma for the energy range from 0.01 to above 100 MeV nucleon-1. For the > 0.1 MeV n-1 ions, the energy dependencies become essential for both ionization and recombination processes. Ionization of the Fe projectile …
The far-infrared emission of radio loud and radio quiet quasars
Wilkes, B. J.; Polletta, M.; Courvoisier, T. J. -L. +1 more
Continuum observations at radio, millimetre, infrared and soft X-ray energies are presented for a sample of 22 quasars, consisting of flat and steep spectrum radio loud, radio intermediate and radio quiet objects. The primary observational distinctions, among the different kinds of quasars in the radio and IR energy domains are studied using large…
The reality of old moving groups - the case of HR 1614. Age, metallicity, and a new extended sample
Holmberg, J.; Feltzing, S.
We prove the existence of the old and metal-rich moving group HR 1614. This is done using the new Hipparcos parallaxes in combination with metallicities derived from Strömgren photometry, supported by dynamical simulations of the evolution of old moving groups in the galactic potential. A new selection criterion for this moving group is presented …
The origin of silicate carbon stars: ISO/SWS observation of V778 Cygni
Waters, L. B. F. M.; Dominik, C.; Yamamura, I. +2 more
The origin of silicate carbon stars has been a mystery ever since their discovery. We discuss here a full grating spectrum between 2.4 and 45 mu m of the silicate carbon star
The puzzling theoretical predictions for the luminosity of clumping He burning stars
Weiss, A.; Prada Moroni, P. G.; Degl'Innocenti, S. +3 more
This paper deals with theoretical predictions for He burning models in a range of masses covering the so-called Red Giant Branch phase transition. Taking as a guideline the observational constraints given by Hipparcos parallaxes to the predicted luminosity of models originated from Red Giant progenitors with He core undergoing electron degeneracy,…
X-rays and regions of star formation: a combined ROSAT-HRI/near-to-mid IR study of the rho Oph dark cloud
Grosso, N.; Bontemps, S.; André, P. +2 more
We have obtained two deep exposures of the rho Oph cloud core region with the ROSAT High Resolution Imager. The improved position accuracy (1arcsec -6arcsec ) with respect to previous recent X-ray observations (ROSAT PSPC, and ASCA ) allows us to remove positional ambiguities for the detected sources. We also cross-correlate the X-ray positions wi…
Wind properties of Wolf-Rayet stars at low metallicity: Sk 41 (SMC)
Crowther, P. A.
The stellar properties of Sk 41 (AB4, WN5h), the only known single Wolf-Rayet star in the SMC, are derived from ultraviolet (IUE), optical (AAT) and near-IR (NTT) spectroscopy. Contrary to expectations for low metal environments, the stellar properties of Sk 41 are typical of equivalent WN stars in the Galaxy and LMC, with T* ~ 42kK, lo…