Publications (13)13.21 Total impact
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Article: Physical parameters of pre-main sequence stars in open clusters
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ABSTRACT: Our aims are twofold: To determine the physical parameters of PMS members in young open clusters (YOCs), and to check and compare the performances of different model isochrones. We compare UBVRI photometric observations of YOCs to theoretical isochrones in the photometric diagrams. The comparison simultaneously provides membership assignments for MS and PMS stars, and estimates for the masses, ages, and spatial distribution of the candidate members. The relations found between the different cluster parameters show that the procedure applied to assign cluster membership, and to measure physical parameters for the selected members, is well founded.05/2011; -
Article: UBVRIJHK photometry of Dolidze 25 (Delgado+, 2010)
VizieR Online Data Catalog. 11/2009; 350:99104. -
Article: Photometry of a stellar cluster near IRAS 07141-092 (Yun+, 2008)
VizieR Online Data Catalog. 03/2008; 348:30209. -
Article: The Nature of the Gould Belt from a Fractal Analysis of its Stellar Population
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ABSTRACT: The Gould Belt (GB) is a system of gas and young, bright stars distributed along a plane that is inclined with respect to the main plane of the Milky Way. Observational evidence suggests that the GB is our closest star formation complex, but its true nature and origin remain rather controversial. In this work we analyze the fractal structure of the stellar component of the GB. In order to do this, we tailor and apply an algorithm that estimates the fractal dimension in a precise and accurate way, avoiding both boundary and small data set problems. We find that early OB stars (of spectral types earlier than B4) in the GB have a fractal dimension very similar to that of the gas clouds in our Galaxy. On the contrary, stars in the GB of later spectral types show a larger fractal dimension, similar to that found for OB stars of both age groups in the local Galactic disk (LGD). This result seems to indicate that while the younger OB stars in the GB preserve the memory of the spatial structure of the cloud where they were born, older stars are distributed following a similar morphology as that found for the LGD stars. The possible causes for these differences are discussed. Comment: 20 pages including 7 figures and 1 table. ApJ (in press)08/2007; -
Article: Pre-main sequence stars in open clusters. I. The DAY-I catalogue
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ABSTRACT: We present the project we are carrying out at present, the search for and characterisation of pre-main sequence (PMS) stars among the members of Galactic young clusters. The observations of 10 southern clusters, nine of them located in the Carina-Sagittarius spiral arm of the Milky Way are presented. We aim at listing candidate PMS member stars in young clusters. The catalogued stars will serve as a basis for future spectroscopic studies of individual objects to determine the properties of stellar formation in the last phases before the main sequence stage. Properties such as the presence of residual envelopes or disks, age spread among PMS members, and the possible presence of several episodes of star formation in the clusters, are to be addressed. Multicolour photometry in the UBVRcIc system has been obtained for 10 southern young clusters in the fourth Galactic quadrant, located between Galactic longitudes l=238 and l=310. For six clusters in the sample, the observations presented here provide the first published study based on CCD photometry. A quantitative comparison is performed with post-MS isochrones, and PMS isochrones from three different evolutionary models are used in the photometric membership analysis for possible PMS stars. The observations produce photometric indices in the Johnson-Cousins photometric systems for a total of 26962 stars. Matching with the 2MASS data base provides astrometric calibration for all stars, and JHK 2MASS indices for 60 per cent of them. Post-MS cluster ages range from 4 to 60 Myr, whereas the photometric membership analysis assigns PMS membership to a total of 842 stars, covering an age range between 1 and 10 Myr. A catalogue, named DAY-I, with the information on the PMS candidate members has been ellaborated. Comment: 15 pages, 10 figures. Accepted in Astronomy and Astrophysics: 30.1.200703/2007; -
Article: PMS stars in open clusters: the DAY-I Catalogue (Delgado+, 2007)
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ABSTRACT: We present the basic ideas and first results from the project we are carrying out at present, the search for and characterisation of pre-main sequence (PMS) stars among the members of Galactic young clusters. The observations of 10 southern clusters, nine of them located in the Carina-Sagittarius spiral arm of the Milky Way are presented. We aim at listing candidate PMS member stars in young clusters. The catalogued stars will serve as a basis for future spectroscopic studies of individual objects to determine the properties of stellar formation in the last phases before the main sequence stage. Properties such as the presence of residual envelopes or disks, age spread among PMS members, and the possible presence of several episodes of star formation in the clusters, are to be addressed. Multicolour photometry in the UBVRcIc system has been obtained for 10 southern young clusters in the fourth Galactic quadrant, located between Galactic longitudes l=238 and l=310. For six clusters in the sample, the observations presented here provide the first published study based on CCD photometry. A quantitative comparison is performed with post-MS isochrones, and PMS isochrones from three different evolutionary models are used in the photometric membership analysis for possible PMS stars. The observations produce photometric indices in the Johnson-Cousins photometric systems for a total of 26962 stars. The matching of our pixel coordinates with corresponding fields in the 2MASS data base provides astrometric calibration for all catalogued stars and JHK 2MASS photometric indices for 60% of them. Post-MS cluster ages range from 4 to 60Myr, whereas the photometric membership analysis assigns PMS membership assignment to a total of 842 stars, covering an age range between 1 and 10Myr. This information on the PMS candidate members has been collected into a catalogue, named DAY-I, which contains 16 entries for 842 stars in the field of 10 southern clusters. (1 data file).VizieR Online Data Catalog. 02/2007; 346:71397. -
Article: Multiwavelength analysis of the young open cluster NGC 2362
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ABSTRACT: We present a multiwavelength analysis of the young open cluster NGC 2362. UBVRcIc CCD photometric observations, together with available data in the Chandra data base, near infrared data from the Two Micron All Sky Survey (2MASS), and recently published Halpha spectroscopy were used to get information about the evolutionary stage of the cluster and the main physical properties of its stellar content. Cluster membership is estimated for every individual star by means of ZAMS and isochrone fitting. The cluster is confirmed to host a richly populated pre-main sequence (PMS), and to contain a large amount of X-ray emitting stars, which reach from the PMS members of GK spectral type, up to the most luminous OB type main sequence (MS) members. The PMS cluster members show no significant age spread, and the comparison to both PMS and post-MS isochrones suggests a younger age for the more massive MS than for lower mass PMS members. The analysis allows to asses the validity of currently used pre-main sequence evolutionary models, and supports the suggestion of a well defined positive correlation of the X-ray emission from PMS stars with their bolometric luminosity. Clear differences are found on the other hand, between the X-ray activity properties of MS and PMS cluster members, both in the relation between X-ray luminosity and bolometric luminosity, and in spectral properties as well. Comment: 1 gzipped file: 1 tex file with 9 pages text. 5 ps files with figures. Submitted to Astrophysical Journal02/2006; -
Article: The intermediate age open cluster NGC 7044
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ABSTRACT: A photometric analysis is conducted of the open cluster NGC 7044, on the basis of UBVR CCD observations of 896 stars in the cluster field. Reddening and metallicity estimates are highly dependent on whether reddening slopes and absorption coefficients vary with spectral type. The color-magnitude diagram obtained is compared with selected sets of isochones, based on evolutionary models computed with and without consideration of convective overshooting from the stellar core during the H and He phases of core burning. Better general agreement is obtained between predicted and observed features of the color-magnitude diagram with overshooting models.The Astronomical Journal 09/1993; 106:1547-1560. · 4.03 Impact Factor -
Article: Reddening effects in Stromgren photometry
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ABSTRACT: The possible existence of systematic errors due to reddening in Stromgren uvby photometric data on B stars is investigated by means of statistical analysis of published observational data on a sample of stars in 17 young open clusters. The data are compiled in tables and graphs and characterized in detail. A linear dependence of the observed reddening slope E(c1)MK/E(b-y)MK on spectral type is found and tentatively attributed to a reddening dependence in the coefficients used to transform instrumental values to standard values.Astronomy and Astrophysics 12/1990; 241:69-76. · 4.59 Impact Factor -
Article: The calibration of intrinsic colours in UVBY photometry
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ABSTRACT: On the basis of photoelectric uvby observations of NGC 1502 and NGC 2169 it is shown that the m0 and (u-b)0 values for early-type members of young open clusters critically depend on the set of standard stars selected to perform the transformation of instrumental to standard magnitudes. In particular, the values of these indices may contain large errors when the calibrations need to be extrapolated due to the cluster reddening. It is shown that these errors should be greatly reduced by using a calibration for (u-b), instead of m1.Astronomy and Astrophysics 06/1989; 219:121-124. · 4.59 Impact Factor -
Article: Structure in the velocity space of globular clusters
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ABSTRACT: We present an analysis of the velocity space of a sample of globular clusters (GC) with absolute proper motions. The vertical component of the velocity is found to be correlated with luminosity and galactocentric radius. We divided the sample into two luminosity groups above and below the peak of the luminosity function (LF), $M_V=-7.5$, for Galactic GCs. The two groups display different kinematic behaviour according to the first and second statitical moments of the velocity distribution as well as distinct velocity ellipsoids. The velocity ellipsoid of the high luminosity clusters is aligned with the symmetry axes of the Galaxy, whereas the minor axis of the Low Luminosity group is strongly inclined relative to the Galactic rotation axis.http://dx.doi.org/10.1051/0004-6361:20010374. -
Article: Analysis of the stellar population in the central area of the HII region Sh 2-284
http://dx.doi.org/10.1051/0004-6361/200912961. -
Article: Book-Review : The Formation of the Milky Way
Irish Astronomical Journal. 23:124.
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Institutions
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1989–2011
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Instituto De Astrofisica De Andalucia
Granada, Andalusia, Spain
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