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Evidence for water ice and estimate of dust production rate in comet Hale-Bopp at 2.9 AU from the Sun
Altieri, B.; Keller, H. U.; Lellouch, E. +7 more
We report observational evidence for water ice in comet C/1995 O1 (Hale-Bopp) when it was at 2.9 AU from the Sun, from emission features at 44 and 65 mu m, and possibly an absorption feature at 3.1 mu m, observed with ISO/LWS and PHT. We find that icy grains have mean radii of 15 mu m within a factor of 2, lifetimes of ~ 2 days, a temperature of ~…
Infrared array photometry of bulge globular clusters. I. Combined ground based JK and HST VI photometry of NGC 6553
Moneti, A.; Montegriffo, P.; Bica, E. +4 more
JK infrared photometry for the bulge globular cluster NGC 6553, combined with high resolution visual VI observations are presented and discussed in connection with the bulge metal rich population. The infrared data were taken with IRAC2 at ESO 2.2m telescope while the optical counterparts are from Hubble Space Telescope (HST). We find a mean magni…
HST/GHRS observations of AM Herculis
Gänsicke, B. T.; Beuermann, K.; Szkody, P. +2 more
We present phase-resolved spectroscopy of AM Herculis obtained with the HST/GHRS when the system was in a high state. The ultraviolet light curve shows a quasi-sinusoidal modulation, which can be explained by a hot spot on the rotating white dwarf. The broad Lyalpha absorption expected for photospheric radiation of a moderately hot white dwarf is …
The HIPPARCOS Hertzsprung-Russell diagram of S stars: probing nucleosynthesis and dredge-up
Jorissen, A.; Udry, S.; Mayor, M. +2 more
HIPPARCOS trigonometrical parallaxes make it possible to compare the location of Tc-rich and Tc-poor S stars in the Hertzsprung-Russell (HR) diagram: Tc-rich S stars are found to be cooler and intrinsically brighter than Tc-poor S stars. The comparison with the Geneva evolutionary tracks reveals that the line marking the onset of thermal pulses on…
Variable sub-arcsecond structure in the circumstellar envelope of IRC+10216
Haniff, C. A.; Buscher, D. F.
We present new diffraction-limited interferometric images of the carbon star IRC+10216 at wavelengths of 2.2 mu m and 3.4 mu m. These show that the distribution of the near-infrared emission from the star departs significantly from a spherical geometry on 0.1 arcsecond scales. At 3.4 mu m, i.e. close to the peak of the star/dust-shell spectral ene…
Fundamental stellar parameters for nearby visual binary stars: eta Cas, XI Boo, 70 OPH and 85 Peg. Helium abundance, age and mixing length parameter for low mass stars
Morel, P.; Baglin, A.; Lebreton, Y. +1 more
The calibration of nearby visual binary stars on the HR diagram is used to determine the helium abundance, age and mixing length parameter for stars other than the Sun. Four Population I low mass systems with high-quality data are analysed by means of standard evolutionary stellar models: eta Cas, 70 Oph, xi Boo and 85 Peg. Complementing these res…
Infrared spectra of carbon stars observed by the ISO SWS. I. Molecular absorption in N-type and SC-type stars
Ohnaka, K.; Tsuji, T.; Aoki, W.
We carried out observations of bright optical carbon stars by the ISO SWS, and detected the absorption features of CO, CS, CH, SiS and HCN in N-type and SC-type stars. We found several characteristics of molecular absorption features corresponding to the spectral types. The CH fundamental bands in 3-4 mu m in N-type stars are stronger than those i…
The kinematically peculiar cores of the Coma cluster early-type galaxies NGC 4816 and IC 4051
Saglia, R. P.; Bender, R.; Wegner, G. +1 more
The Coma cluster is one of the richest known cluster of galaxies, spanning about 4 dex in density. Hence it is the ideal place to study the structure of galaxies as a function of environmental density in order to constrain the theories of galaxy formation and evolution. For a magnitude limited sample of 35 E and S0 galaxies we obtained long slit s…
Modelling the Cloverleaf: contribution of a galaxy cluster at Z ~ 1.7
Kneib, J. -P.; Antonucci, R.; Alloin, D. +3 more
We present a new investigation of the Cloverleaf (z=2.558) based on the combination of archival HST/WFPC2 data, recent IRAM CO(7-6) maps and wide field CFHT/FOCAM images. The deepest WFPC2 observation (F814W) shows a significant overdensity of I814W ~ 23--25 galaxies around the Cloverleaf that we interpret as the presence of a cluster o…
Solar H i Lyman alpha full disk profile obtained with the SUMER/SOHO spectrometer
Wilhelm, K.; Curdt, W.; Lemaire, P. +2 more
An uncalibrated solar hydrogen Lyman alpha profile was obtained with the use of the spectrometer on SOHO. The collection of the light scattered by the telescope permitted to average the profile over the full solar disk. The profile taken at the L1 Sun-Earth Lagrangian position is free of the central geocoronal absorption. Then, taking a…