Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1
Context: .About 5% of upper main sequence stars are permeated by astrong magnetic field, the origin of which is still matter of debate. Aims: . With this work we provide observational material to studyhow magnetic fields change with the evolution of stars on the mainsequence, and to constrain theory explaining the presence of magneticfields in A and B-type stars. Methods: . Using FORS1 inspectropolarimetric mode at the ESO VLT, we have carried out a survey ofmagnetic fields in early-type stars belonging to open clusters andassociations of various ages. Results: . We have measured themagnetic field of 235 early-type stars with a typical uncertainty of 100 G. In our sample, 97 stars are Ap or Bp stars. For thesetargets, the median error bar of our field measurements was 80 G.A field has been detected in about 41 of these stars, 37 of which werenot previously known as magnetic stars. For the 138 normal A and B-typestars, the median error bar was 136 G, and no field was detected in anyof them.
| Radial Velocities and Kinematic Membership in the Open Cluster NGC 3114
Echelle spectroscopic observations for 30 bright stars in the field ofthe sparse open cluster NGC 3114 are presented. The sample includesmain-sequence stars, yellow and red giants, and blue stragglercandidates. Radial velocities are derived by cross-correlations usinghigh signal-to-noise ratio standard spectra as templates. The clustermean velocity is well defined from eight giants and severalmain-sequence stars whose average is =-3.52+/-0.25 kms-1. The membership probabilities of the observed stars arecomputed on the basis of the velocity distributions of the cluster andfield stars, and the expected percentage of contamination at eachposition. We classified 19 cluster members and 10 nonmembers; theremaining star is a known spectroscopic binary for which no membershipprobability was assigned. Among the members, there is a bright yellowgiant, seven red giants, and four blue straggler candidates, althoughthey should be considered as turn-off stars. The location of two of themin the color-magnitude diagram (slightly blueward of the turn-off) canbe explained by their low rotational velocities. No velocity variationswere detected in the 16 stars measured more than once, which indicatesthat NGC 3114 possess an abnormally low binary frequency. From spectraltypes of cluster members, a distance modulus (V-Mv)=9.8+/-0.2mag and a reddening E(B-V)=0.07+/-0.01 mag are derived. The cluster ageis estimated to be 1.6×108 yr. The observationspresented here were obtained at the Complejo Astronómico ElLeoncito (CASLEO), which is operated under agreement between the ConsejoNacional de Investigaciones Científicas y Técnicas de laRepública Argentina (CONICET) and the National Universities of LaPlata, Córdoba and San Juan.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Photometry of F-K type bright giants and supergiants. 3: The luminosity, reddening, and heavy element abundance of GK stars
The reddening, luminosity, and heavy element abundance of 250 brightgiants and supergiants of type GK are discussed on the basis of 4 color,DDO, RI, and Geneva photometry Bright giants of type GK with age greaterthan 5 x 108 yr, and of type G0/3 with age greater than 2 x108 yr, are very scarce in the solar neighborhood. The medianspace motion vectors of the bright giants and supergiants with welldetermined space motions are (U, V, W) = (+10.6, -13.2, -7.7) +/- (12.3,8.8, 8.8) km/s. The M1 index for 4 color photometry, whencorrected for luminosity (gravity) effects, is sensitive to heavyelement abundance of the GK stars but may not be reliable for those oftype G0/3. The available spectroscopic determinations of (Fe/H) givemixed results with the two largest samples being internally consistentbut with a large zero-point difference. There is a similar zero-pointshift in the peak frequency of the photometrically determined values ofP(Fe/H) for the F type and for the GK type stars. There is littleevidence for an appreciable galactic, radial gradient in the P(Fe/H)values. A previously noted correlation of the heavy element abundanceindex, delta M1, with the amplitude defect in the B lightcurves of Cepheids, FB, and interpretation of the(PLFB) relation as a (PL(Fe/H)) relation needs furtherinvestigation in light of the apparent sensitivity of M1 toFe/H for the F stars (the domain of the Cepheids with P less than 10 d)and lack of this sensitivity for the G0/3 star (domain of the Cepheidswith P greater than 10 d).
| Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
Not Available
| Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
Not Available
| 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.
| Catalog of AP and AM stars in open clusters
The previous results of Raab (1922), Markarian (1951), and Collinder(1931) have been used to catalog Ap and Am stars that are in the fieldof open clusters. Tabular data are presented for the clusterdesignation, the HD or HDE number, the right ascension (1900), thedeclination (1900), and the magnitude. Also listed are the spectraltypes and, for certain stars, the probability of cluster membership.
| Photoelectric search for CP2-stars in open clusters. XIII - NGC 3114 and IC 2602
Delta-a photometric observations of two open clusters, obtained usingthe 50-cm and 1-m telescopes at ESO during 1981-1984, are reported. Thedata are presented in extensive tables and graphs and brieflycharacterized. Of the 168 stars measured, eight (six in NGC 3114 and twoin IC 2602) are identified as chemically peculiar upper-main-sequenceobjects with magnetic fields. These hot CP2 stars are found to beblueshifted relative to the cluster main sequences on the V/(b-y)diagrams.
| Stromgren photometry of open clusters. IV - NGC3114 and additional measurements for IC2602
Stromgren photometry of 122 B- and A-type stars in the southern opencluster NGC3114 up to V = 12.mag is presented. The membership of theobserved stars is discussed; a mean reddening of E(b-y) = 0.043 for thecluster is estimated; and the behavior of CP stars in the color diagramsis investigated. Furthermore, additional measurements for 16 stars inthe cluster IC2602 are given, and the membership of these stars isexamined.
| Chemically peculiar stars in open clusters. I - The catalog
The largest existing compilation is presented of Ap and Am open clusterstars. The catalog contains information on 381 chemically peculiar (CP)stars of the upper main sequence in 79 open clusters. The catalog iscomposed of the following tables: (1) the main body, which lists CP (orsuspected CP) stars which are kinematical (or suspected kinematical)members of open clusters; (2) the list of CP (or suspected CP) starssometimes numbered among cluster members but which are actuallykinematical nonmembers; (3) the list of stars sometimes designated as'peculiar' but, in fact, probably not CP; (4) references for numberingsystems of cluster stars; (5) references for membership; and (6)references for spectral and/or peculiarity types.
| Statistical Investigation of Chemically Peculiar Stars - Part Four - Luminosity of Different Type Stars
Not Available
| Evidence of decay of the magnetic fields of AP stars
Data obtained in the Geneva photometric system (Rufener, 1981) andappropriate calibrations of this system in terms of surface magneticfield and gravity are used to provide, on the basis of 708 field andcluster Ap stars, observational evidence that these stars undergo decayof their magnetic field on an evolutionary timescale. Justifications aregiven for the application of a photometric gravity calibration topeculiar stars. The dependence of the photometrically estimated surfacemagnetic field on gravity is found to differ markedly from availabletheoretical calculations. HgMn stars are found to show the same trend,strengthening the impression that they might be slightly magnetic.He-weak stars do not.
| Photometric properties of AP stars in the Geneva system
An examination of the properties in some photometric diagrams of morethan 600 Ap stars measured in the Geneva photometric system confirm thatthe Balmer discontinuity is smaller than for normal stars, along withthe link between a proposed peculiarity parameter and both rotationalvelocity and effective magnetic field. It is shown that the peculiarityparameter is sensitive to interstellar reddening, and it is foundthrough examination of the standard deviations for visual magnitudesthat cool CP 2 stars without Eu peculiarity have the greatestamplitudes. Rapid rotators have a mild peculiarity, while positivecorrelation exists for Si and SrCr stars.
| Intermediate Band Photometry of the Open Cluster NGC3114
Abstract image available at:http://adsabs.harvard.edu/abs/1982PASP...94..232S
| Radial Velocities of the Mass of NGC3114 Measured on the Objective-Prism of the 40-CM ESO
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981A&AS...44..101A&db_key=AST
| Relative radial velocities from objective prism spectra in the region of nine southern open star clusters and a star field at Eta Carinae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41..245G&db_key=AST
| NGC 3114 : another open cluster possibly rich in peculiar stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80..807L&db_key=AST
| New AP Stars in NGC 3114
Not Available
| Photometric Observations of NGC 3114
Not Available
| Not Available
Not Available
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Hajógerinc |
| Rektaszcenzió: | 10h01m41.76s |
| Deklináció: | -60°06'46.6" |
| Vizuális fényesség: | 7.799 |
| Távolság: | 699.301 parszek |
| RA sajátmozgás: | -9.7 |
| Dec sajátmozgás: | 4.5 |
| B-T magnitude: | 7.809 |
| V-T magnitude: | 7.8 |
Katalógusok és elnevezések:
|
