Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Integrated spectral evolution of Galactic open clusters
We present a library of 47 open-cluster integrated spectra, mostlyobtained at CASLEO (San Juan, Argentina) in the range 3600 < λ< 7400 Å, which are made available at CDS. The data arecombined with previous spectra to obtain 10 high signal-to-noise ratiobasic templates in the young and intermediate-age domains, which arealso provided in the library. These Galactic disc templates representthe increased time resolution spectral evolution of a stellar populationunit around the Solar metallicity level. The improved signal-to-noiseratio of the present templates with respect to previous template lists,together with their increased time resolution, allowed us to improve thefundamental parameters of some open clusters. The present spectrallibrary will be useful for several astrophysical applications,particularly for population syntheses of star-forming giant galaxies.
| BVI photometry and integrated spectroscopy of the very young open clusters Ruprecht 119, NGC 6318 and BH 245
We present CCD BVI observations obtained for stars in the fields of theunstudied or poorly studied open clusters Ruprecht 119, NGC 6318, and BH245 projected close to the direction towards the Galactic centre. Wemeasured V magnitude and B-V and V-I colours for about 600 starsreaching down to V ~ 19 mag. From the analysis of the colour magnitudediagrams, we confirmed the physical reality of the clusters and derivedtheir reddening, distance and age for the first time. In addition, weobtained flux-calibrated integrated spectra in the range 3500-9200Å for the cluster sample. Using the equivalent widths of theBalmer lines and comparing the cluster spectra with template spectra wederive both foreground reddening and age. The photometric andspectroscopic results reveal that the three studied objects are veryyoung open clusters with ages ranging between 10 and 15 Myr, which havealready undergone the HII region evolutionary phase and are dominated bythe upper MS stars. The clusters, located between 1.1 kpc and 3.3 kpcfrom the Sun, are affected by different amounts of interstellar visualabsorption (2.4 <= A_v <= 7.0). In particular, BH 245 turned outto be a highly reddened open cluster located at a distance of scarcely1.1 kpc. Based on observations made at the University of Toronto (DavidDunlap Observatory) 24inch telescope, Las Campanas, Chile, and at theComplejo Astronómico El Leoncito, which is operated underagreement between the Consejo Nacional de InvestigacionesCientíficas y Técnics de la República Argentina andthe National Universities of La Plata, Córdoba, and San Juan,Argentina.
| Photometric and integrated spectral study of the young open clusters Pismis 22, NGC 6178, NGC 6216 and Ruprecht 130
We present CCD observations in the B, V , and I passbands obtained forstars in the fields of the open clusters Pismis 22, NGC 6178, NGC 6216,and Ruprecht 130, projected not far from the Galactic centre (|l| <30̂, |b| < 2̂). The sample consists of about 790 starsreaching down to V ~ 18-19 mag. From the analysis of the colourmagnitude diagrams, we confirmed the physical reality of the clustersand derived their reddening, distance and age. In addition, we obtainedflux-calibrated integrated spectra in the range 3500-9200 Å forthe cluster sample. The equivalent widths of the Balmer lines providedus with age estimates, while the comparison with template spectraallowed us to derive both foreground reddening and age. The photometricand spectroscopic results reveal that the four studied objects are youngopen clusters with ages ranging between 35 and 50 Myr. The clusters,located between 1.0 kpc and 4.3 kpc from the Sun, are affected bydifferent amounts of interstellar visual absorption (0.6 ≃Av ≃ 6.0). Based on observations made at ComplejoAstronómico El Leoncito, which is operated under agreementbetween the Consejo Nacional de Investigaciones Científicas yTécnicas de la Repúbica Argentina and the NationalUniversities of La Plata, Córdoba, and San Juan, Argentina, andat the University of Toronto (David Dunlap Observatory) 24-inchtelescope, Las Campanas, Chile. Tables 3-6 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| A Photometric and Spectroscopic Study of the Southern Open Clusters PISMIS 18, PISMIS 19, NGC 6005, and NGC 6253
CCD observations in the B, V, and I passbands have been used to generatecolor-magnitude diagrams (CMDs) for the southern open cluster candidatesPismis 18, Pismis 19, and NGC 6005, as well as for the old open clusterNGC 6253. The sample consists of about 1550 stars reaching down to V ~19 mag. From analysis of the CMDs, the physical reality of the threecluster candidates is confirmed and their reddening, distance, and ageare derived, as well as those of NGC 6253. In addition, integratedspectra for Pismis 18, Pismis 19, and NGC 6253 covering a range from3500 to 9200 Å were obtained. The reddening, age, and metallicityof these three clusters were derived from Balmer and Ca ii tripletequivalent widths by comparing the observed spectra with those oftemplate clusters. The photometric and spectroscopic results allow us toconclude that Pismis 18, Pismis 19, and NGC 6005 are intermediate-age (t~ 1 Gyr), genuine open clusters, while NGC 6253 has an age t ~ 5 Gyr.All these clusters are located approximately toward the Galactic center,between 1.5 and 2.7 kpc from the Sun. Their metallicities range overvalues that are typical of moderately metal-poor to moderatelymetal-rich open clusters.
| Integrated spectral study of reddened globular clusters and candidates
This paper presents integrated spectra in the range 6700 - 9500Angstroms for 20 Galactic globular clusters (and candidates) in thebulge and 5 others projected on the Galactic disk (|l|>30mbox{^{\circ}}\ and |b|<5mbox {^{\circ}}). Most of them are considerablyreddened and are among those least studied in the literature. We derivereddening and metallicity from flux-calibrated spectra, thus providingindependent information of that derived through colour-magnitudestudies. For some clusters in the sample, these parameters have beendetermined for the first time, and for others a considerable revision isgiven. We indicate the globular clusters which definitely belong to thebulge metal-rich and intermediate metallicity families. Among theobjects projected on the disk, we find that the integrated spectralproperties of Lyng\aa 7, BH 176 and Palomar 10 are compatible with thoseof metal-rich globular clusters. Finally, ESO 93-SC08 is an old opencluster, and UKS 2 is an open cluster with age ~1 Gyr. Based onobservations made at the Complejo Astronómico El Leoncito(CASLEO), Argentina, and European Southern Observatory (ESO), Chile.
| Fundamental parameters of the highly reddened young open clusters Westerlund 1 and 2
We study the compact open clusters Westerlund1 (BH197) and Westerlund2.We present CCD integrated spectroscopy for both clusters, and CCDimaging in the V and I bands for the former one. So far, Westerlund1 ispossibly the most reddened open cluster studied in detail (Av~ 13.0). It has an age of 8 +/- 3 Myr and a distance from the Sun ofd_sun ~ 1.0 +/- 0.4 kpc. For Westerlund2 we derive a visual absorptionAV~ 5.0 mag, an age of 2-3 Myr, and d_sun=5.7+/- 0.3 kpc.From luminosity and structural arguments we conclude that Westerlund1,although young and compact, it is a massive cluster, in contrast toWesterlund2. Based on observations made at Complejo AstronómicoEl Leoncito, which is operated under agreement between the ConsejoNacional de Investigaciones Cientificas y Tecnicas de la RepublicaArgentina and the Universities of La Plata, Cordoba and San Juan,Argentina, and at the University of Toronto (David Dunlap Observatory)24-inch telescope, Las Campanas, Chile. The photometric observations areavailable at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/Abstract.html
| CCD Stromgren Photometry of Young Reddened Clusters
The capabilities of CCD uvby photometry for the study of reddened youngclusters are investigated. Observations of four fields in the directionof the clusters Basel 1, Berkeley 86, NGC 6704, and NGC 6756, with atotal of 1665 stars measured in at least the y and b bands, produce newestimates for the clusters parameters. The results are compared to thosefrom previously published studies in different photometric systemsshowing good agreement in the values of color excess and distancemodulus, with the exception of NGC 6756, for which an essentially largerdistance is found. Furthermore, the ages estimated for this cluster,Basel 1, and NGC 6704 are found to be higher than previously assumed, inparticular for the last one. The presence of red giants as clustermembers is suggested in Basel 1, NGC 6704, and NGC 6756.
| The B jRI Photometric System
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..281G&db_key=AST
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Three globular cluster candidates in the direction of the bulge shown to be small emission nebulae.
We carried out spectrophotometry in the range 4000-7000A and V, I andGunn z imaging of the initially thought to be globular clustercandidates in the direction of the Galactic bulge TJ5 and TJ23 (Terzan& Ju 1980) and the one reported by Bica (1994). The three objectsturned out to be small nebulae in rich stellar fields. Diagnosticdiagrams for emission line ratios indicate that TJ5 and TJ23 areplanetary nebulae. The locus of the third object strongly suggests it tobe a supernova remnant, with very strong [NII]lambda6584_ andstrong [SII]lambdaλ6717,31_. The sizes of the nebulaeare d=28", 45"and 49", and the reddening derived from the Balmerdecrement indicates E(B-V)=0.86, 1.81 and 0.19, respectively for TJ5,TJ23 and the supernova remnant.
| Photometry of Stars in the Field of V345 and V553 Aquilae
Not Available
| Photometry of Stars in the Field of the Mira XY Aquilae
Not Available
| Photometry of Stars in the Field of the Mira YZ Draconis
Not Available
| UBV photometry of hot white dwarf stars
Johnson UBV photometry has been obtained for a set of hot degeneratestars, primarily DA and DO white dwarfs from among those detected in thePalomar-Green survey of UV excess objects. Most of our program starshave estimated effective temperatures (Teff) in the range22,000 to 80,000 K and have no previous photometry. Some objectsselected are also x-ray and extreme ultraviolet sources from the ROSATall sky survey. The importance of precise photometric measurements inthe analysis of x-ray data is discussed. A discrepancy between theobserved colors and predicted colors is noted, and possibly accountedfor by difficulties in defining the atmospheric cutoff of the U band anda general lack of hot stars used to define the photometrictransformation between theoretical and observed colors.
| Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
| UBV(RI)c photometry of equatorial standard stars - A direct comparison between the northern and southern systems
UBV(RI)c photometry of 212 stars from Landolt's list of equatorialstandards is presented. The observations are tied to the system definedby Cousin's E-region standards. A comparison of the present results withLandolt's reveals reasonably good agreement for (V-R)c and (V-I)c, butmarked systematic differences for (B-V) and (U-B). The UBV systems ofCousins and Landolt are evidently not the same and both probably differfrom Johnson's original system.
| Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
| The 77-81 intermediate-band photometric system
The 77-81 intermediate-band photometric color system for the study oflate-type stars is defined. The passbands are centered on a region ofTiO absorption at 7750 A (77) and on a region of CN absorption at 8100 A(81). Good agreement is found between measurements made on the 77-81system with different detectors. The 77-81 color is well correlated withM type and reasonably correlated with carbon-richness class. The 77-81,V-I color-color diagram clearly distinguishes M and C types from otherstars. It is also shown that the 77-81 color may be used to measure TiOband strength.
| Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
| Spectrophotometry of stars of intermediate brightness
Spectrophotometric observations of 15 stars in a magnitude range m ofbetween 8.0 and 10.9, located mostly near the equator and covering allthe range of right ascensions, are presented. The energy distributionshave been obtained in Hayes' (1970) system as revised by Hayes andLatham (1975), and in the augmented system presented by Taylor (1984).Comments about some of the standard stars are presented as well as acomparison of the results obtained with both systems.
| UBVRI photometric standard stars around the celestial equator
It is pointed out that accurate, internally consistent, and readilyaccessible standard star photometric sequences are necessary for thecalibration of the intensity and color data which astronomers obtain atthe telescope. The photometric results provided in connection with thepresent study represent the first part of an effort which is concernedwith the presentation of UBVRI photoelectric photometric standard starsin the magnitude range from 7 to 17 over as broad a range in color aspossible. All of the photometric observations were made with a 31034type photomultiplier used in a pulse counting mode. Some 15 to 25standard stars chosen from Cousins' lists (1973, 1976) in the E-regionswere observed with an 0.4-m telescope each night along with the programstars. UBVRI standard stars were observed periodically throughout thenight. Observations with a 0.9-m telescope were also conducted. TheUBVRI photoelectric observations take into account 223 stars.
| Optical observations of ultraviolet objects. II - Classification and photometry /l = 0 to 145 deg/
UBV photometry and MK spectral classification are presented for a sampleof stars originally selected as UV objects from satellite photometrywith the S2/68 experiment. Although most stars of the sample arespectroscopically normal, a number of hot, subluminous stars were alsofound. Radial velocities are given for some of the stars observed. It isproposed that the majority of the apparently normal early B stars athigh galactic latitudes which are not runaway stars are subluminousdisc-population analogues of horizontal branch B stars of Population II.
| Equivalent widths and rotational velocities of southern early-type stars
Not Available
| Studies in Galactic STRUCTURE.II.LUMINOSITY Classification for 1270 Blue Giant Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJS....2...41M&db_key=AST
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Yilanci |
| Sað Açýklýk: | 17h38m40.64s |
| Yükselim: | +04°20'09.8" |
| Görünürdeki Parlaklýk: | 9.042 |
| özdevim Sað Açýklýk: | 7.8 |
| özdevim Yükselim: | 8.6 |
| B-T magnitude: | 9.008 |
| V-T magnitude: | 9.04 |
Kataloglar ve belirtme:
|
