Search Publications
The Potsdam contribution to the extragalactic link of the HIPPARCOS pr oper motion system
Scholz, R. -D.; Schilbach, E.; Hirte, S.
Absolute proper motions of 360 Hipparcos stars in 24 fields well distributed over the northern sky were derived from measurements of photographic plates taken mainly with the Tautenburg Schmidt telescope (134/200/400 cm). In each field (about 10 square degrees) a large number of galaxies was used to link the proper motions to the extragalactic ref…
The Bonn contribution to the extragalactic link of the HIPPARCOS proper motion system.
Tucholke, H. -J.; Brosche, P.; Odenkirchen, M.
In order to calibrate the proper motions of the Hipparcos astrometry satellite, our group has measured accurate absolute proper motions of Hipparcos stars in small fields around optically bright extragalactic radio sources or bright galaxies with star-like features. In addition, we also use fields where relative proper motions are calibrated by me…
Astrometric positions of stars with high proper motions in the Southern Hemisphere
Rousseau, J. M.; Perie, J. P.
Several stars with large proper motions, cited by W.J. Luyten, were included in the preliminary programme for the HIPPARCOS mission. When performing preparatory measurements of plates, difficulties were encountered in identifying certain of these stars when relying only on published coordinates. We have taken advantage of this work which relates t…
Interactive Deconvolution with Error Analysis (IDEA) in astronomical imaging: Application to aberrated HST images on SN 1987A, M 87 and 3C 66B
Roques, S.; Fraix-Burnet, D.; Bouyoucef, K.
The regularized reconstruction algorithm {Interactive Deconvolution with Error Analysis} (IDEA) is presented. One of its main advantages is to control the error propagation and to provide an estimation of the quality of the deconvolved image. IDEA is compared with two popular probabilistic methods: Richardson-Lucy and Maximum Entropy. These three …
Long- and short-term variability in O-star winds. I. Time series of UV spectra for 10 bright O stars.
Kaper, L.; Henrichs, H. F.; Nichols, J. S. +3 more
An atlas of time series of ultraviolet spectra is presented for 10 bright O stars. The spectra were obtained with the International Ultraviolet Explorer during seven observing campaigns lasting several days over a period of 6years. The UV P Cygni lines in 9 out of the 10 studied stars exhibit a characteristic pattern of variability in the form of …
The β Pictoris phenomenon among Herbig Ae/Be stars. UV and optical high dispersion spectra.
Talavera, A.; McCollum, B.; Sitko, M. L. +10 more
We present a survey of high dispersion UV and optical spectra of Herbig Ae/Be (HAeBe) and related stars. We find accreting, circumstellar gas over the velocity range +100 to +400km/s, and absorption profiles similar to those seen toward β Pic, in 36% of the 33 HAeBe stars with IUE data as well as in 3 non-emission B stars. We also find evidence of…
Planetary nebulae in the Magellanic Clouds. I. Carbon abundances and TypeI PNe.
Dennefeld, M.; Leisy, P.
We present optical and ultraviolet spectroscopic observations of planetary nebulae (PNe) in the Large (LMC) and the Small Magellanic Clouds (SMC). For the visible spectra with highest S/N, line intensities have been measured to a few tenths of a percent of Hbeta_. UV spectra are used for the determination of carbon abundances. This pape…
A new maximum likelihood method for luminosity calibrations.
Luri, X.; Figueras, F.; Torra, J. +1 more
A new statistical parallax method using the Maximum Likelihood principle is presented, allowing the simultaneous determination of a luminosity calibration, kinematic characteristics and spatial distribution of a given sample. This method has been developed for the exploitation of the Hipparcos data and presents several improvements with respect to…
Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images. III. Photometric properties.
Tagliaferri, G.; Pasquini, L.; Pallavicini, R. +2 more
We present high-precision UBV(RI)_c_ photometry for a sample of active stars detected serendipitously by the EXOSAT satellite. Fourteen objects, out of 47 likely optical counterparts, turned out to be clearly variable, with periods in the range 1-8 days, including a newly discovered eclipsing binary. For most of them the optical variability is con…
The canonical X-ray/gamma-ray spectrum of Seyfert 1s and low-state Galactic black hole candidates.
Zdziarski, A. A.; Magdziarz, P.; Gierlinski, M. +1 more
We review broad-band X-ray/γ-ray spectra of radio-quiet Seyfert 1s as well as of Galactic black hole candidates in the low state. The spectra share their basic components: an underlying power law, a Compton-reflection component with an Fe Kα line, low-energy absorption by cold matter, and a high-energy cutoff above ~200keV. The X-ray energy spectr…