Open clusters with Hipparcos. I. Mean astrometric parameters
New memberships, mean parallaxes and proper motions of all 9 openclusters closer than 300 pc (except the Hyades) and 9rich clusters between 300 and 500 pc have been computed using Hipparcosdata. Precisions, ranging from 0.2 to 0.5 mas for parallaxes and 0.1 to0.5 mas/yr for proper motions, are of great interest for calibratingphotometric parallaxes as well as for kinematical studies. Carefulinvestigations of possible biases have been performed and no evidence ofsignificant systematic errors on the mean cluster parallaxes has beenfound. The distances and proper motions of 32 more distant clusters,which may be used statistically, are also indicated. Based onobservations made with the ESA Hipparcos astrometry satellite
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A comprehensive variability study of the enigmatic WN8 stars - Final results
As a conclusion of our all-sky variability survey of the 'enigmatic'variable WN8 stars, we have carried out coordinated multisitephotometric and spectroscopic observations of WN8 stars in 1989 and1994-1995. We confirm the leading role of the stellar core inrestructuring the whole wind. This emerges as a statistical trend: thehigher the level of the continuum (i.e., core) light variations, thehigher the variability of the P Cygni edges of the optical emissionlines. However, the form of the correlation between the light andprofile variations is generally different for each individual star. Thehigh level of activity of WN8 stars may be supported/induced bypulsational instability.
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The enigmatic WN8 stars: Intensive photometry of four southern stars on time scales from 30 min to 3 months
We present the first results of an extensive photometric study of themost intrinsically variable Wolf-Rayet (WR) stars: the WN8 subclass.Some 375 individual differential observations of WR16 and WR40 wereobtained over a contiguous interval of approximately 3 months in anarrow visual continuum bandpass. Over the same interval, we obtainedroughly 200 broadband V observations of the fainter WN8 stars WR66 andWR82. All four WN8 stars show significant random variability on timescales of hour to approximately a day -- probably related to thestochastic formation, propagation, and decay of emitting/scatteringinhomogeneities in the winds. Unlike for WR66 and WR82, the photometricbehavior of WR16 and WR40 is more deterministic with approximately twopossible periods in the range approximately 2-30 days -- possiblyrelated to some kind of Luminous Blue Variable (LBV), binary, orrotation phenomenon. In addition, WR82 shows a possible secular declineduring the 3 months and WR66 reveals a clear periodicity of 3.51 h. Thisshort period may be related to nonradial pulsations or a spiral-inbinary process invoking a low-mass, compact companion as seen in themassive x-ray binary Cyg X-3, a WN7 + c system of period 4.8 h.
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Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
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WR 22 is an Eclipsing Binary Star
Not Available
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Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
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Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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High-velocity interstellar gas in the lines of sight to the Wolf-Rayet stars HD 97152 and HD 96548
The interstellar medium was studied in the direction to the WR stars HD96548 and HD 97152, and the results are reported. New observational dataon the UV spectra of several field stars near both these WR stars arepresented. The high-velocity gas seen in the spectra of these starssuggests that the detected expanding interstellar gas structure consistsof two OB cluster supershells. The presence of high-velocity absorptioncomponents in one of five field star spectra in the direction of themore isolated WR star HD 96548 suggests that this expanding gas does notoriginate from the optical ring nebula RCW 58 surrounding HD 96548, aspreviously believed, but instead indicates the detection of a previouslyunknown expanding interstellar shell in this line of sight.
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Analysis of the photometric variability of WR40
New photometric data on the star WR40 are presented and, together withdata already published, are analyzed in a detailed and homogeneousmanner in order to investigate the variability of the star. Goodevidence is presented for the existence of a periodicity P = 6.250 + or- 0.078 day with a semiamplitude of 0.010 mag in the Stromgren b filter.Only part of the 0.1 mag peak-to-peak variation of the star can beexplained in this way and other interesting features of the variabilityare outlined. The physical origin of the periodicity is discussed.
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Expanding shells of interstellar gas in the lines-of-sight to Wolf-Rayet stars
High-velocity interstellar gas was detected in the directions toward theWR stars HD 97152 and HD 96548 by interstellar resonance absorptionlines in high-resolution IUE spectra. Shifted line components in thespectra of 5 field stars covering an area of 2 deg around HD 97152exhibit velocities up to -150 km/sec. The presence of numerous otherearly-type stars in this region plus an analysis of IRAS image datasuggest that this expanding interstellar structure is a stellarwind-blown shell which may be unrelated to the WR star. High-velocitygas seen in the line-of-sight to HD 96548 does not originate from thestar's optical ring nebula (RCW 58) but from a large, expandinginterstellar shell at least 40 pc in diameter. With velocities up to-120 km/sec and a location well off the galactic plane, thisinterstellar gas may be a highly evolved supernova remnant like thatassociated with the WR star HD 50896.
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Merged log of IUE observations.
Not Available
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Precision photometric monitoring of southern variable Wolf-Rayet stars with a comment on the overall continuum variability of WR stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987AJ.....94.1008L&db_key=AST
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