Search Publications
Evidence for two classes of comets from their polarimetric properties at large phase angles.
Levasseur-Regourd, A. C.; Hadamcik, E.; Renard, J. B.
The dependence of the linear polarization of solar light scattered by cometary dust upon the phase angle has been studied, through appropriate fits, from a data base of 22 comets and 750 points (mainly in the green and red spectral domains). Although the whole coma polarization is found to slightly increase with the wavelength, all the data obtain…
Infrared spectrophotometry of M 17 with ISOCAM.
Palazzi, E.; Perault, M.; Abergel, A. +4 more
We report spectrophotometric observations of the HII region/neutral medium interface in M 17 obtained with the ISOCAM Circular Variable Filter (CVF) in the spectral range 5.15 to 16.5µm. The lines of singly-ionized species come mainly from the clumpy "neutral" interface, while the HII region dominates the line emission by higher-ionization s…
SWS observations of solid CO_2_ in molecular clouds.
Lutz, D.; Heras, A. M.; Prusti, T. +29 more
We report absorption features of solid CO_2_ stretching and bending modes in several lines of sight, including embedded young stellar objects and the Galactic Center source Sgr A*. The overall CO_2_ abundance in ices is ~15% relative to H_2_O. Profile shapes are consistent with the presence of grain mantles with distinct polar (H_2_O-rich) and non…
2.5-45µm SWS spectroscopy of the Circinus Galaxy.
Lutz, D.; Genzel, R.; Sturm, E. +5 more
We present 2.5-45µm ISO SWS spectra of the Circinus galaxy which is one of the closest spirals containing both a visually obscured Seyfert nucleus and circumnuclear starburst activity. In addition to PAH features, H_2_ and low excitation ionic lines ([FeII], [NeII], [SIII]) from the starburst region its spectrum shows several prominent lines…
ULYSSES plasma parameters: latitudinal, radial, and temporal variations.
Goldstein, B. E.; Neugebauer, M.; Phillips, J. L. +6 more
Observations by the Ulysses SWOOPS plasma experiment are used to investigate spatial and temporal gradients during the mission, with emphasis on more recent high latitude observations including the recent South Pole to North Pole passage during solar minimum. Compared to lower latitudes, the high latitude solar wind had higher average speed, proto…
Calibration and performance of the ISO Long-Wavelength Spectrometer.
Omont, A.; Ade, P. A. R.; Liseau, R. +52 more
The wavelength and flux calibration, and the in-orbit performance of the Infrared Space Observatory Long-Wavelength Spectrometer (LWS) are described. The LWS calibration is mostly complete and the instrument's performance in orbit is largely as expected before launch. The effects of ionising radiation on the detectors, and the techniques used to m…
Spectral analysis of hot helium-rich white dwarfs.
Werner, K.; Dreizler, S.
We present a model atmosphere analysis of most known hot helium-rich white dwarfs of spectral type DO. The stars represent the non-DA white dwarf cooling sequence from the hot end (T_eff_=~120000K) down to the DB gap (T_eff_=~45000K). From medium resolution optical spectra, effective temperatures, surface gravities, and element abundances are dete…
A search for interstellar gas-phase CO_2_. Gas: solid state abundance ratios.
de Graauw, T.; van Dishoeck, E. F.; Salama, A. +15 more
We present searches for gas-phase CO_2_ features in the ISO-SWS infrared spectra of four deeply embedded massive young stars, which all show strong solid CO_2_ absorption. The abundance of gas-phase CO_2_ is at most 2x10^-7^ with respect to H_2_, and is less than 5% of that in the solid phase. This is in strong contrast to CO, which is a factor of…
Long-term spectroscopic monitoring of BA-type supergiants. I. Halpha_ line-profile variability.
Stahl, O.; Wolf, B.; Kaufer, A. +5 more
We have obtained time series of spectra in the wavelength range 4000-6800 A over several months with high S/N and high resolution in wavelength (λ/{DELTA}λ=~20000) and time ({DELTA}t=~1d) of the late-type B and early-type A supergiants HD91619 (B7Ia), βOri (B8Ia), HD96919 (B9Ia), HD92207 (A0Ia), HD100262 (A2Ia) and αCyg (A2Ia). Halpha_ …
Spectral analyses of late-type WC central stars of planetary nebulae.
Hamann, W. -R.; Jeffery, C. S.; Leuenhagen, U.
The optical spectra of the seven late-type Wolf-Rayet central stars NGC40 ([WC8]), BD+30 3639 ([WC9]), He2-99 ([WC9]), CPD-56 8032, He2-113, M4-18 and K2-16 (all [WC11]) are analyzed by means of spherically expanding model atmospheres. The NLTE simulations account for the elements helium, carbon and oxygen. As main results effective temperature T_…