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HST observations of blue Straggler stars in the core of the globular cluster M 3.
Burgarella, D.; Cacciari, C.; Buonanno, R. +7 more
The core of the Galactic Globular Cluster M 3 (NGC 5272) has been observed with the WFPC2 through the filters F255W, F336W, F555W, and F814W. Using these observations along with a thorough reanalysis of earlier catalogs, we have produced a catalog of blue straggler stars (BSS) spanning the cluster. Earlier studies and the fainter part of our sampl…
Patchy intergalactic He II absorption in HE 2347-4342. II. The possible discovery of the epoch of He-reionization
Reimers, D.; Wamsteker, W.; Rodriguez-Pascual, P. +3 more
We report on observations of redshifted Heii303.8 Angstroms absorption in the high-redshift QSO HE2347-4342 (z=2.885, V=16.1) with the Goddard High Resolution Spectrograph on board HST in its low resolution mode (bigtriangleup lambda = 0.7 Angstroms). With f_λ=3.6\ 10(-15) ergcm(-2) s(-1) Angstroms(-1) at the expected position of Heii304 Angstroms…
The HIPPARCOS catalogue as a realisation of the extragalactic reference system
Zacharias, N.; Kozhurina-Platais, V.; Hemenway, P. D. +23 more
The paper describes the methods and observations by which the Hipparcos Catalogue was linked to the International Celestial Reference System (ICRS). The contributions of several groups represented in the authorship of this paper, using a variety of techniques, were synthesised in order to determine the global orientation and rotation (spin) of the…
Cataclysmic variables in the ROSAT PSPC All Sky Survey.
Verbunt, F.; Bunk, W. H.; Ritter, H. +1 more
91 cataclysmic variables from a sample of 162 systems with known or suspected binary periods were detected during the ROSAT XRT-PSPC All Sky Survey. Among the non-magnetic systems, the X-ray to optical/ultraviolet flux ratio decreases along the sequence SU UMa type - U Gem type - Z Cam type - UX UMa type, due mainly to variations in the optical/ul…
Fundamental parameters of Wolf-Rayet stars. VI. Large Magellanic Cloud WNL stars.
Crowther, P. A.; Smith, L. J.
We present a detailed, quantitative study of late WN (WNL) stars in the LMC, based on new optical spectroscopy (AAT, MSO) and the Hillier (1990A&A...231..111H) atmospheric model. In a previous paper (Crowther et al. 1995A&A...293..172C), we showed that 4 out of the 10 known LMC Ofpe/WN9 stars should be re-classified WN9-10. We now present …
Warm molecular envelope of M giants and Miras: a new molecule forming region unmasked by the ISO SWS.
Ohnaka, K.; Yamamura, I.; Tsuji, T. +1 more
Our observations with the ISO SWS revealed that H_2_O band at 2.7µm appears as absorption already in an M2 giant β Peg and strengthens towards later M giants. Further, CO_2_ 4.2µm band appears as absorption in an M7 giant SW Vir and especially strong in a Mira variable S Vir. The excitation temperatures of these molecular bands estimat…
The TYCHO Catalogue
Makarov, V. V.; Bastian, U.; Fabricius, C. +9 more
The principal observational characteristics of the Tycho Catalogue, and a summary of its main astrometric and photometric properties, are presented. Median astrometric standard errors (in position, parallax, and annual proper motion) are typically around 7mas for stars brighter than V_T_~9mag, and approximately 25mas for V_T_~10.5mag, at the catal…
β Pictoris revisited by Hipparcos. Star properties.
Crifo, F.; Ferlet, R.; Vidal-Madjar, A. +2 more
Observations with the Hipparcos satellite allowed a new determination of the β Pictoris distance. This star is located at 19.28+/-0.19pc, a value close to the upper limit of previous evaluations. The overall consequences are briefly discussed; in particular it is concluded that in the frame of standard stellar evolution models, there is no need fo…
First results of ISO-SWS observations of Saturn: detection of CO_2_, CH_3_C_2_H, C_4_H_2_ and tropospheric H_2_O.
Beintema, D. A.; Lellouch, E.; Encrenaz, T. +16 more
The spectrum of Saturn has been recorded between 4.5 and 16.0µm with the grating mode of the Short-Wavelength Spectrometer (SWS) of ISO. The resolving power is 1500. The main results of this observation are (1) the detection of CO_2_, CH_3_C_2_H and C_4_H_2_ in the stratosphere and (2) the detection of H_2_O in the troposphere. In the 4.5-5.…
Coordinated ultraviolet and Hα spectroscopy of bright O-type stars.
Kaper, L.; Kambe, E.; Fullerton, A. W. +7 more
As part of our search for the origin of stellar-wind variability, we have conducted simultaneous ultraviolet and Hα spectroscopy of a number of bright O stars. The observed changes in the Hα line occur at low velocity (0-0.2vinfinity_) on timescales that are characteristic of the development and evolution of discrete absorption componen…