X-rays from the open cluster NGC 6633
NGC 6633 is a young, open cluster with a similar age to the Hyades andPraesepe, but probably a lower metallicity. We present the results ofROSAT High Resolution Imager observations of an optically selectedcatalogue of likely members of NGC 6633. 8 out of 51 NGC 6633 membershave been detected, with main-sequence spectral types A to G, above athreshold X-ray luminosity of~6-12×1028ergs-1. We find that NGC 6633 doesnot contain cool stars that are as X-ray luminous as the most activeobjects in the Hyades and that the median X-ray luminosity of F-G starsin NGC 6633 is less than that in the Hyades, but probably greater thanin Praesepe. However, when X-ray activity is expressed as the X-ray tobolometric flux ratio we find that NGC 6633 and the Hyades are verysimilar and display similar peak levels of coronal activity. Weattribute this discrepancy to a number of possible wide binary systemswith higher X-ray (and bolometric) luminosities in the Hyades sample andeither a low metallicity in NGC 6633, which makes its cool stars bothX-ray and bolometrically less luminous at the same colour, or a distanceto NGC 6633 that has been underestimated, which would decrease stellarX-ray luminosities without changing X-ray to bolometric flux ratios.
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Radial velocities of stars in open clusters
A CORAVEL type spectrometer was used to measure precise radialvelocities of 116 late-type stars of spectral classes F5 - M5 in thefields of 18 open clusters. Probable cluster members were selected onthe basis of kinematic and photometric data. New or improved radialvelocities for 12 open clusters were thus obtained.
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CA II H and K measurements made at Mount Wilson Observatory, 1966-1983
Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during theyears 1966-1983. These results are derived from 65,263 individualobservations of 1296 stars. For each star, for each observing season,the maximum, minimum, mean, and variation of the instrumental H and Kindex 'S' are given, as well as a measurement of the accuracy ofobservation. A total of 3110 seasonal summaries are reported. Factorswhich affect the ability to detect stellar activity variations andaccurately measure their amplitudes, such as the accuracy of the H and Kmeasurements and scattered light contamination, are discussed. Relationsare given which facilitate intercomparison of 'S' values with residualintensities derived from ordinary spectrophotometry, and for convertingmeasurements to absolute fluxes.
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Red giants in open clusters. I - Binarity and stellar evolution in five Hyades-generation clusters: NGC 2447, 2539, 2632, 6633, and 6940
The present analysis for membership-determination and binary-detectionof radial velocity observations for 62 red giant stars in the HyadeslikeNGC 2447, 2539, 2632, 6633, and 6940 open clusters has yielded a binarypercentage of the order of 25-33 percent. Twelve orbits have beendetermined, and two triple systems identified. At least nine of the tenstars found in the Hertzsprung gap are composite binaries of the (gK +dA) type; the radial velocity dispersion in each cluster is close to thevalue expected on the basis of the virial theorem, assuming typicalvalues of the total mass of 1000 solar masses, and of a half-mass radiusof 3 pc.
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Galactic cluster star radial velocities obtained with a focal reducer field spectrograph. I - The clusters IC 1805, NGC 2287, NGC 2548, IC 4665, NGC 6633, NGC 6940 and NGC 7092
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...62..301G&db_key=AST
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Radial Velocities of Bright Southern Stars - Part Two - 53 Late-Type HR and FK4 Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&AS...52..479A&db_key=AST
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Spectral types in the open cluster NGC 6633
Spectral types are given for the 26 brightest stars in the region of NGC6633. Only two of the giants are definitely cluster members. Twoapparent blue stragglers are present, as well as one extreme Ap star,four marginal Am stars, and two stars with weak shell lines.
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Four-colour UVBY and H-beta photometry of field stars - Double-lined spectroscopic binaries, G type dwarfs and early type FK4 stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...29..313O&db_key=AST
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Bright southern stars of astrophysical interest
The paper lists a number of bright peculiar stars in the SouthernHemisphere discovered on 20-A/mm spectrograms. Recent information isalso given for a few known peculiar objects. The lists include: oneLambda Boo star, 4 Hg and other Bp stars, 7 Am stars, 17 shell oremission-line stars, and 37 double-lined spectroscopic binaries, amongwhich are two triple-lined, four composite, eight variable or eclipsing,and three peculiar shell and/or emission-line systems.
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(R-I) colors of cepheids and yellow supergiants in open clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...203..466S&db_key=AST
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Membership of the open cluster NGC 6633
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS....9..213S&db_key=AST
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Southern open clusters II. UBV and Hbeta photometry of 11 clusters between galactic longitudes 259d and 280d
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS....9...97V&db_key=AST
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Catalogue des étoiles mesurées dans le système photométrique de l'Observatoire de Genève
Not Available
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The Galactic Cluster, NGC 6633.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958ApJ...127..539H&db_key=AST
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Relative proper motions of stars in the region of the open cluster NGC 6633.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958AJ.....63..387V&db_key=AST
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Untersuchung der offenen Sternhaufen IC 4665, NGC 6633, IC 4756
Not Available
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