Hyades Morphology and Star Formation
Perryman and collaborators found that for the Hyades cluster thefraction of multiple stars increases from G stars to early-A stars. Wediscuss here whether this may be a general property of star formation orwhether collisions in the cluster environment change the fractions ofbinary stars. A star ring of mainly F and G stars is seen around theHyades cluster core, supposedly created by a shock wave due to asupernova explosion. These ring stars show the same fraction of binarystars as observed for the F and G stars in the core of the cluster. Thissuggests that collisions in the high stellar density cluster center didnot measurably change the multiple-star fractions. There is so far onlyevidence of this one supernova explosion in the Hyades. If this isindeed the only one, then only one massive star was born in the cluster.There are also fewer than 10 white dwarf descendants of B stars found inthe cluster. Unless many white dwarfs and neutron stars evaporated fromthe cluster, the initial mass function for stellar masses >2Msolar must have been very steep, corresponding to a Salpeterfunction with an exponent of less than -3.3.
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The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
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Interstellar extinction in the direction of the open cluster IC 348 and the Per OB2 association
The relationship between interstellar extinction and distance in thedirection of dark clouds in the areas around the open cluster IC 348 andthe association Per OB2 is determined using the results of photoelectricphotometry of 189 stars in the Vilnius photometric system. Two absorbinglayers are found. The nearest layer, covering the whole area around IC348, shows the mean extinction A(V) of about 0.7 mag. It begins at thedistance of 160 pc and probably is an extension of the Taurus darkclouds to the northwest. The second absorbing layer has the form of achain of dark condensations named L1468, L1470, and L1471 and is at 260pc distance. This layer has a higher density, its mean extinction beingabout 2.0 mag. The cluster IC 348 is at about the same distance and isphysically related to the dark cloud L1470. The distance of the Per OB2association is found to be 340 pc and the mean extinction of its membersis 0.95 mag. A model of the spatial distribution of the Perseus andTaurus dark clouds based on photometric distance determinations in thisand previous papers is proposed. Six stars in the IC 348 area aresuspected to have emission in the H-alpha line.
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The catalogue of equivalent line widths in the spectra of A- and F-stars.
Not Available
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Spectroscopic determination of metallicity in the star-members of young open clusters.
Not Available
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Peculiar stars in the association Per OB2.
Not Available
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Spectroscopic studies of stars in Per OB2.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977AJ.....82..598G&db_key=AST
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Uvbyβ Photometry of Stars in the Direction of the Association Perseus OB 2
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..656R&db_key=AST
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A Study of the II Persei Association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960ApJ...132...58S&db_key=AST
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INHABITED SKY
