目录
图像
上传图像
DSS Images Other Images
相关文章
Lacerta OB1 Revisited
This investigation utilizes precise uvby? photometry and therecently recalculated Hipparcos data to provide an improved homogeneousdistance scale for the apparent groups of young stars in Lacerta. Allexisting uvby? photometry for stars earlier than A0-type in a20°×20° field centered at l=100°, b=-15° iscollated and the individual stellar distances and color excesses areobtained. The association Lac OB1 is reliably identified as a verycompact young group of 12 bright stars at an average distance of520±20(s.e.) pc. The available radial velocity and proper motionmeasurements strongly support the impression that the group is real. Thestars in the northeast part of Lacerta seem not to represent a physicalgroup, but rather a layer of field stars spread between 140 and 400 pcand extending farther than that toward l˜104°. An estimate of678±50(s.e.) pc of the distance to the open cluster NGC 7243 isobtained based on the brightest cluster members. The calculateddistances are based on a well-tested procedure, and thus represent aclarification over the range of distance existing in the literature forthe bright stars in the Lacerta field. Although a better agreement isnow evident between the photometric distances and the recalculatedHipparcos parallaxes in comparison to the original Hipparcos data,discrepancies still exist for this particular field.
| Catalogue of Ap, HgMn and Am stars
We present a catalogue of 8205 known or suspected Ap, HgMn and Am stars.This paper is a major update of our first edition of the catalog of Apand Am stars and includes revised identifications, additional stars andrevised information obtained from the literature.Catalogue (full Table 1) is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/498/961
| Searching for links between magnetic fields and stellar evolution. III. Measurement of magnetic fields in open cluster Ap stars with ESPaDOnS
Context: A small fraction of upper main sequence stars have strong,highly structured magnetic fields. The origin and evolution of thesefields are not adequately understood. Aims: We are carrying out asurvey of magnetic fields in Ap stars in open clusters in order toobtain the first sample of magnetic upper main sequence stars withprecisely known ages. These data will constrain theories of fieldevolution in these stars. Methods: A survey of candidate open clustermagnetic Ap stars was carried out using the new ESPaDOnSspectropolarimeter at the CFHT. This instrument provides an alternativeto the FORS1 spectropolarimeter used up to now for this survey. Results: We have obtained 44 measurements of the mean longitudinalfields < Bz > of 23 B6-A2 stars that have beenidentified as possible Ap stars and that are possible members of openclusters, with a median uncertainty of about 45 G. Of these stars, 10have definite field detections. Nine stars of our sample are found notto be magnetic Ap stars. These observations significantly increase theinformation available about low-mass stars near the TAMS compared to ourprevious sample. Conclusions: We find that ESPaDOnS provides fieldmeasurements comparable to those that we have previously obtained withFORS1, and that these data also contain a large amount of usefulinformation not readily obtained from lower resolutionspectropolarimetry. With the new data we are able to expand theavailable data on low-mass, relatively evolved Ap stars, and identifymore robustly which observed stars are actually magnetic Ap stars andcluster members. Re-analysis of the enlarged data set of cluster Apstars indicates that such stars with masses in the range of 2-5{M_ȯ} show rms fields larger than about 1 kG only when they arenear the ZAMS. The time scale on which these large fields disappearvaries strongly with mass, ranging from about 250 Myr for stars of 2-3{M_ȯ} to 15 Myr for stars of 4-5 {M_ȯ}. Our data areconsistent either with emergent flux conservation for most (but not all)Ap stars, or with modest decline in flux with age.Based on observations made with theCanada-France-Hawaii Telescope, operated by the National ResearchCouncil of Canada, the Centre National de Recherche Scientifiqueof France, and the University of Hawaii, under programme 05A-C19.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Memberships and CM diagrams of the open cluster NGC 7243
The results of astrometric and photometric investigations of the opencluster NGC 7243 are presented. Proper motions of 2165 stars withroot-mean-square error of 1.1;mas yr-1 were obtained by meansof PDS scanning of astrometric plates covering 97 years. A total of 211cluster members down to V=15.5;mag have been identified. V and Bmagnitudes have been determined for 2118 and 2110 stars respectively.Estimations of mass (348 Msun <=M_TOT <=522Msun), age (t=2.5x 108 yr), distance (r=698 pc)and reddening (EB-V=0.24) of the cluster NGC 7243 have beenmade.Table 8 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) orhttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/401/531
| 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
| Catalogue of blue stragglers in open clusters.
An extensive survey of blue straggler candidates in galactic openclusters of both hemispheres is presented. The blue stragglers wereselected considering their positions in the cluster colour-magnitudediagrams.They were categorized according to the accuracy of thephotometric measurements and membership probabilities. An amount of 959blue straggler candidates in 390 open clusters of all ages wereidentified and classified. A set of basic data is given for everycluster and blue straggler. The information is arranged in the form of acatalogue. Blue stragglers are found in clusters of all ages. Thepercentage of clusters with blue stragglers generally grows with age andrichness of the clusters. The mean ratio of the number of bluestragglers to the number of cluster main sequence stars is approximatelyconstant up to a cluster age of about 10^8.6^ yr and rises for olderclusters. In general, the blue stragglers show a remarkable degree ofcentral concentration.
| Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
Not Available
| General catalogue of AP and AM stars
A catalog of all the known Ap and Am stars, containing a total of 6684objects, was prepared. The few stars that were wrongly considered as Apor Am star are noted as well as some others for which their identity asAp or Am stars is not yet well established. The catalog gives theidentificators and the main observational data for each star, includingthe magnitude, color, spectral type, duplicity, periodicity, magneticfield, and projected rotational velocity.
| Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
Not Available
| 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.
| 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.
| Photoelectric search for CP2-stars in open clusters. XII - Alpha Persei, Praesepe and NGC 7243
Observations of 95 stars in the open clusters Alpha Persei, Praesepe,and NGC 7243 have been performed by Delta-a photometry in order tosearch for the presence of the 5200-A feature of CP2 (or CP4) stars.Although peculiarity has been claimed for half a dozen stars in AlphaPersei, the photometry detects only the CP4 star (= He-weak) HL 985among the cluster members. The behavior of 3 Be/shell stars (HL 861,1164, 904) concerning the 5200-A feature is discussed. Praesepe, by farthe oldest cluster in the survey program, presents a very new andspecial case: 3 stars, previously classified as Am have Delta-a valuesaround 0.020 mag, i.e., they exhibit photometric peculiarity likeCP2-stars. Such values are incompatible with preceding results for fieldand cluster Am-stars (= CP3). These objects deserve further attentionboth photometrically and spectroscopically. NGC 7243 exhibits anoutstanding high frequency of CP2-stars; two certain Delta a-peculiarstars have been found: L 370, already known as peculiar, and the newlyidentified L 114. Two stars are near the detection level: L 58 and 121.According to Geneva photometry, L 487 is markedly peculiar.
| 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.
| HY equivalent widths in the open cluster NGC 7243
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..376H&db_key=AST
| A spectroscopic and photometric investigation of NGC 7243.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..110H&db_key=AST
| Untersuchungen der offenen Sternhaufen NGC 7092 (M 39), NGC 7209, und NCG [sic] 7243
Not Available
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
