Search Publications
Modelling irradiance variations from the surface distribution of the solar magnetic field
Solanki, S. K.; Unruh, Y. C.; Fligge, M.
An important question in solar physics is to what extent solar surface magnetism affects the solar irradiance. Previous attempts to answer this question have employed proxies of the magnetic field to reconstruct the irradiance and compare it with observations. Here we present the first model calculations of solar irradiance variations based on var…
Exploring the brown dwarf desert with Hipparcos
Queloz, D.; Arenou, F.; Udry, S. +2 more
The orbital elements of 11 spectroscopic binaries with brown dwarf candidates (M2 sin i between 0.01 and 0.08 Msun) are combined with the Hipparcos observations in order to derive astrometric orbits. Estimations of the masses of the secondary components are thus calculated. It appears that 5 secondary masses are more than 2 s…
2.5-11 micron spectroscopy and imaging of AGNs. Implication for unification schemes
Altieri, B.; Clavel, J.; Metcalfe, L. +6 more
We present low resolution spectrophotometric and imaging ISO observations of a sample of 57 AGNs and one non-active SB galaxy over the 2.5-11 mu m range. The sample is about equally divided into type I (<= 1.5; 28 sources) and type II (> 1.5; 29 sources) objects. The mid-IR (MIR) spectra of type I (Sf1) and type II (Sf2) objects are statisti…
Implications of the cosmic infrared background for light production and the star formation history in the Universe
Lagache, G.; Puget, J. L.; Gispert, R.
The Cosmic Background due to the integrated radiation from galaxies over the whole life of the Universe is reviewed. We find that this background is well constrained by measurements. The total power in the background is in the range 60-93 nWm-2sr-1. The data show the existence of a minimum separating the direct stellar radiat…
A proper motion study of the globular cluster ω Centauri
Freeman, K. C.; van Leeuwen, F.; Le Poole, R. S. +2 more
A proper motion study is presented of the globular cluster ω Centauri. Based on 100 plates obtained with the Yale-Columbia 66 cm (26 inch) refractor, and ranging in epoch from 1931 till 1935 and 1978 till 1983, differential proper motions are obtained for 9847 stars. The limiting magnitude (photographic) is 16.0 for the centre of the cluster, 16.5…
The structure of the collapsing envelope around the low-mass protostar IRAS 16293-2422
Ceccarelli, C.; Caux, E.; Tielens, A. G. G. M. +4 more
Using H2O, OI and SiO data, we derive the structure of the collapsing envelope around the low-mass protostar IRAS16293-2422 down to r ~ 30 AU. With an accurate model which computes self-consistently the chemical composition, thermal balance and line emission from a collapsing envelope (Ceccarelli et al. 1996), we find that IRAS16293-242…
Multiple shells in IRC+10216: shell properties
Mauron, N.; Huggins, P. J.
We report on the properties of the multiple shells in the circumstellar envelope of IRC+10216, using deep optical imaging, including data from the Hubble Space Telescope. The intensity profiles confirm the presence of thin ( ~ 0farcs5 -3'' ec), limb-brightened shells in the envelope, seen in stellar and ambient Galactic light scattered by dust. Th…
Slow magnetoacoustic waves in coronal loops
Berghmans, D.; Nakariakov, V. M.; Verwichte, E. +1 more
A theoretical model interpreting propagating disturbances of EUV emission intensity, recently observed in coronal loops, is constructed in terms of slow magnetoacoustic waves. The model is one-dimensional and incorporates effects of nonlinearity, dissipation due to finite viscosity and thermal conduction, and gravitational stratification of plasma…
Probing the brown dwarf population of the Chamaeleon I star forming region
Neuhäuser, R.; Comerón, F.; Kaas, A. A.
We present observations of a sample of 13 very low mass stars and brown dwarfs in the central region of the Chamaeleon I star forming cloud. The observations include slitless spectroscopy around Hα to identify new members, low resolution long-slit visible and near-infrared spectroscopy, deep ROSAT PSPC X-ray observations, and ISOCAM mid-infrared o…
ISO-SWS observations of OMC-1: H_2 and fine structure lines
Bertoldi, F.; Drapatz, S.; Rosenthal, D.
Using the Short-Wavelength-Spectrometer on the Infrared Space Observatory (ISO), we obtained near- and mid-infrared spectra toward the brightest H_2 emission peak of the Orion OMC-1 outflow. A wealth of emission and absorption features were detected, dominated by 56 H_2 ro-vibrational and pure rotational lines reaching from H_2 0-0 S(1) to 0-0 S(2…