Search Publications
Follow-up photometry of six new beta Cephei stars discovered from the HIPPARCOS mission
Aerts, C.
We present ground-based follow-up photometry in the Geneva seven-colour photometric system of six new candidate beta Cep stars. The variability of these objects was originally found from the HIPPARCOS mission. From the new data we are able to confirm their beta Cep-type nature, to detect the pulsational frequencies and to identify most of the degr…
Structure and evolution of low-mass Population II stars
D'Antona, F.; Montalbán, J.; Mazzitelli, I.
The focus of the present paper is on the detailed description of the internal structures of low mass, population II stars, to clarify some issues about these stellar models and, mainly, their present reliability for observational comparisons. We then explore 1) the role of the local convective model; 2) the differences between "grey" and "non grey…
Far-infrared photometry and mapping of Herbig Ae/Be stars with ISO
Burkert, A.; Ábrahám, P.; Henning, Th. +2 more
Seven Herbig Ae/Be stars were observed at mid- and far-infrared wavelengths with ISOPHOT, the photometer on-board the Infrared Space Observatory. At λ{<=}25µm, where the emission mainly arises from a compact circumstellar region, the observed spectral energy distributions can be described by power-law relationships between wavelength and …
A young stellar group associated with HD 199143 (d=48 pc)
McCollum, B.; de Winter, D.; van den Ancker, M. E. +1 more
We present new optical and ultraviolet spectroscopy of the anomalous EUV emitter HD 199143 (F8V). High resolution spectra in the Halpha and Na I D wavelength regions show evidence for very rapid (a few hundred km/s) rotation of the stellar photosphere. Using archive IRAS data we also show that the star has excess emission above photospheric levels…
ISOPHOT Serendipity Survey observations of interstellar clouds I. Detection of the Coldest Cores in Chamaeleon
Krause, O.; Lemke, D.; Laureijs, R. J. +5 more
ISOPHOT Serendipity Survey (ISOSS) observations at 170 \um\ reveal cold dust clouds in the nearby star forming region Chamaeleon. The distribution of the ISOSS/IRAS based T(I170/I100) colour temperature have been studied in a nearby low-mass star forming region. T(I170/I100) separates the obscured and in…
Infrared, radio and optical variability of the BL Lacertae object 2007+777
Quirrenbach, A.; Wagner, S. J.; Zensus, J. A. +8 more
We present infrared observations at wavelengths of 60 and 100 mu m and contemporaneous radio (five frequencies) and optical (R band) monitoring of the BL Lac object 2007+777. During a three-week campaign with the ISO, the VLA, the Effelsberg 100 m radio telescope, and optical telescopes in Heidelberg and on Calar Alto, Spain, we observed variabili…
A detailed spectroscopic analysis of varepsilon Per. I. Determination of the orbital parameters and of the frequencies
Mathias, P.; Aerts, C.; De Cat, P. +1 more
We present the analysis of 445 high signal-to-noise spectra of the Si III triplet at 4553 Ä, 4568 Ä, 4575 Ä of the line-profile variable star varepsilon Persei. The data were gathered during 14 consecutive nights and fully cover the orbital cycle of the binary. The orbital parameters that we derive from our data for the close binary are in full ag…
Kinematical trends among the field horizontal branch stars
de Boer, Klaas S.; Altmann, Martin
Horizontal branch (HB) stars in the field of the Milky Way can be used as tracers for the study of early stages of the evolution of our galaxy. Since the age of individual HB stars is not known a priori, we have studied the kinematics of a sample of field HB stars measured with Hipparcos to look for signs of age and population nature. Our sample c…
Deep far infrared ISOPHOT survey in ``Selected Area 57". I. Observations and source counts
Nørgaard-Nielsen, H. U.; Ábrahám, P.; Lemke, D. +7 more
We present here the results of a deep survey in a 0.4 deg2 blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO at both 60 mu m and 90 mu m. The resulting sky maps have a spatial resolution of 15 x 23 arcsec2 per pixel which is much higher than the 90 x 90 arcsec
Resolved stellar populations of super-metal-rich star clusters in the bulge of M 31
Magain, P.; Jablonka, P.; Sarajedini, A. +3 more
We have applied the MCS image deconvolution algorithm (Magain et al. 1998) to HST/WFPC2 V, I data of three M 31 bulge globular clusters (G170, G177, and G198) and control fields near each cluster. All three clusters are clearly detected, with an increase in stellar density with decreasing radius from the cluster centers; this is the first time tha…