Search Publications

Pulsating and nonpulsating stars in Hyades observed by HIPPARCOS satellite

Antonello, E.; Pasinetti Fracassini, L. E.

A study of the stars in the instability strip of Hyades cluster has been performed taking into account the new estimate of the stellar parallaxes. For taking advantage of the improved accuracy of the distances and hence absolute magnitudes it is necessary to separate the photometric effects of close companions, which appear quite common in Hyades.…

The He⁺/H⁺ Abundance in the Orion Nebula from Infrared Space Observatory Measurements

Dufour, Reginald J.; Rubin, Robert H.; Colgan, Sean W. J. +1 more

Using the Short Wavelength Spectrometer on the Infrared Space Observatory, we measured in the Orion Nebula several components of the He I Brα transition, the first detections to the best of our knowledge in an H II region, and the H I Brα line. A value of He⁺/H⁺=0.085+/-0.003 is inferred from these data and is typical of prev…

Properties of the Young Stellar Object N 160 A-IR

Siebenmorgen, R.; Stecklum, B.; Fitzpatrick, E. L. +3 more

We present near- and mid-infrared images of the young stellar object N 160 A-IR in the Large Magellanic Cloud (LMC). For the first time, the YSO is seen in the NIR as a compact point source in the north-western part of the H ii region N 160 A. Furthermore, we present ISO-SWS spectra pointed on the YSO. The spectra cover the full wavelength range o…

Hipparcos data for two open clusters containing cepheids

Lindegren, L.; Lyngå, G.

Using proper motion data from the Hipparcos satellite it is shown that the cepheids S Nor and U Sgr are members of the open clusters NGC 6087 and M 25, respectively. The precision of the Hipparcos data is needed to conclusively carry out a membership test. Parallax data, also obtained from Hipparcos, do not contradict the proper motion results.

ISOCAM Imaging of LBVS

Waters, L. B. F. M.; Trams, N. R.; Voors, R. H. M.

Low-dimensional dynamics outside the laboratory: The case of roAp stars

Boyd, P. T.; Mindlin, G. B.; Merener, N.

In this work, we build a nonlinear model to account for the time variable energy flux of a class of pulsating stars which is simple and robust, and test it against recent observations made with the Hubble Space Telescope. By the construction of a standard global normal form for the model, we not only check that the model has solutions qualitativel…

On the Reliability of Ring Diagram Analysis

Chou, Dean-Yi; Gonzalez Hernandez, I.; Patron, J. +1 more

A comparison between the results of applying a ring diagram analysis to two data sets is described in order to check the quality of the two sets and the reliability of the method. The series used have been obtained with two different helioseismological instruments with the same spatial resolution. A section of 30 × 30 deg2 about the disk center ha…

HST/WFPC2 observation of the core of M 3: Blue objects and the position of the radio source

Ferraro, F. R.; Fusi Pecci, F.; Laget, M. +1 more

HST/WFPC2 images of the central part of the globular cluster M 3 (NGC 5272) in UV (F255W), U (F336W), V (F555W) and I (F814W) are used to search for faint blue stars down to an UV magnitude slightly below the turnoff level. Three low-luminosity blue stars are found in the PC1 field of view; two are new detections. All are within ~ 10arcsec from th…

Cassini Plasma Spectrometer Investigation

Coates, A. J.; Grande, M.; Johnson, R. E. +22 more

Cassini/Huygens is a joint project of NASA and the European Space Agency designed to explore the Saturnian system in depth during its four-year mission. Cassini, the orbiter spacecraft, will carry twelve hardware investigations while Huygens, the Titan atmospheric probe, will carry an additional six. The Cassini Plasma Spectrometer (CAPS), one of …

Insights into the accretion flow in QS Telescopii (RE1938-461) from HST observations

Gänsicke, B. T.; de Martino, D.; Mason, K. O. +3 more

We present HST/FOS observations of the polar QS Tel (RE1938-461) revealing new details in its 140min UV orbital variability. A colour-dependent continuum orbital modulation as well as a narrow dip in its light curve, occurring at the same orbital phases as the one detected in the EUVE band, are observed. Their spectral dependence allows us to iden…