CCD photometric search for peculiar stars in open clusters

Paunzen, E.; Netopil, M.; Iliev, I. Kh.; Maitzen, H. M.; Claret, A.; Pintado, O. I.

doi:10.1051/0004-6361:20053287

Cited by 18 publications

(29 citation statements)

References 23 publications

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“…Together with NGC 3105 and Berkeley 11 of earlier ∆a investigations (Paunzen et al 2005b;, the cluster Ruprecht 44 in the current sample is farthest from the galactic centre (∼10.7 kpc), applying a value of R 0 = 8.0. We have to note that the R GC data for NGC 3105 in Paunzen et al (2005b) was wrongly given as 11.4 instead of 11.0 using R 0 = 8.5. Examining their CP stars content in respect to the investigated total members, lead to 1.6, 2.1 and 5.6% for Ruprecht 44, NGC 3105, and Berkeley 11, respectively, neglecting questionable candidates.…”

Section: Discussionmentioning

confidence: 50%

“…Of special interest is the influence of metallicity, taking its gradients within the galactic disc into account (Chen et al 2003). Together with NGC 3105 and Berkeley 11 of earlier ∆a investigations (Paunzen et al 2005b;, the cluster Ruprecht 44 in the current sample is farthest from the galactic centre (∼10.7 kpc), applying a value of R 0 = 8.0. We have to note that the R GC data for NGC 3105 in Paunzen et al (2005b) was wrongly given as 11.4 instead of 11.0 using R 0 = 8.5.…”

Section: Discussionmentioning

confidence: 85%

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CCD photometric search for peculiar stars in open clusters

Netopil¹,

Paunzen²,

Maitzen³

et al. 2006

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Context. We continue our survey of magnetic chemically peculiar (CP2) stars in galactic open clusters to shed more light on their origin and evolution. Aims. To study the group of CP2 stars, it is essential to find these objects in different galactic environments and at a wide range of evolutionary stages. The knowledge of open cluster ages and metallicities can help for finding a correlation between these parameters and the (non-)presence of peculiarities, which has to be taken into account in stellar evolution models. Methods. The intermediate band ∆a photometric system samples the depth of the 5200 Å flux depression by comparing the flux at the centre with the adjacent regions with bandwidths of 110 Å to 230 Å. It is capable of detecting magnetic CP2 and CP4 stars with high efficiency, but also the groups of (metal-weak) λ Bootis and classical Be/shell stars can be successfully investigated. In addition, it allows the age, reddening, and distance modulus to be determined with appropriate accuracy by fitting isochrones. Results. From the 1677 observed members of the eight open clusters, one Ae and twenty-five CP2 stars were identified. Furthermore nineteen deviating stars are designated as questionable for several reasons. The estimated age, reddening, and distance for the programme clusters were compared with published values of the literature and discussed in this context. Conclusions. The current paper shows that CP2 stars are continuously present in very young (7 Myr) to intermediate age (500 Myr) open clusters at distances greater than 2 kpc from the Sun.

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Section: Discussionmentioning

confidence: 50%

Section: Discussionmentioning

confidence: 85%

CCD photometric search for peculiar stars in open clusters

Netopil¹,

Paunzen²,

Maitzen³

et al. 2006

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“…The basic CCD reductions and a point-spread-function fitting were carried out within standard IRAF V2.12.2 routines on Personal Computers running under LINUX. The way calculation of the normality line, derivation of the errors as well as the calibration of our (g 1 − y) as well as y measurements is the same as in previous works (see Netopil et al 2005;and Paunzen et al 2005b).…”

Section: Observations Reduction and Used Methodsmentioning

confidence: 99%

CCD photometric search for peculiar stars in open clusters

Paunzen¹,

Netopil²,

Iliev

et al. 2006

A&A

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Aims. The detection of magnetic chemically peculiar (CP2) stars in open clusters of the Milky Way can be used to study the influence of different galactic environments on the (non-)presence of peculiarities, which has to be taken into account in stellar evolution models. Furthermore it is still unknown if the CP2 phenomenon evolves, i.e. does the strength of the peculiarity feature at 5200 Å increase or decrease with age. Methods. We have observed eight young to intermediate age open clusters in the ∆a photometric system. This intermediate band photometric system samples the depth of the 5200 Å flux depression by comparing the flux at the center with the adjacent regions having bandwidths of 110 Å to 230 Å. The ∆a photometric system is most suitable to detect CP2 stars with high efficiency, but is also capable of detecting a small percentage of non-magnetic CP objects. Also, the groups of (metal-weak) λ Bootis, as well as classical Be/shell stars, can be successfully investigated. This photometric system allows one to determine the age, reddening and distance modulus by fitting isochrones. Results. Among the presented sample of eight galactic clusters, we have detected twenty three CP2, eight Be/Ae and eight metalweak stars. Another six objects show a peculiar behaviour which is most probably due to a non-membership, variability or duplicity. Fitting isochrones to ∆a photometry yields estimates of the age, reddening and distance that are in excellent agreement with published values.Key words. stars: chemically peculiar -stars: early-type -techniques: photometric -Galaxy: open clusters and associations: general IntroductionThe continuation of our CCD ∆a photometric survey to detect chemically peculiar (CP) stars of the upper main sequence currently comprises the largest sample of open clusters, including young and intermediate age clusters at a variety of galactic longitudes and galactocentric distances.The ∆a photometric system allows one to efficiently detect CP stars and related objects through the flux depression at 5200 Å (Kupka et al. 2004). The efficiency of this system was recently investigated by Paunzen et al. (2005a) surveying a large sample of published field star measurements, resulting in a probability of up to 95% of detecting all relevant magnetic CP stars. Furthermore the groups of λBootis and classical Be/shell systematically show negative ∆a values.Unambiguous detection or non-detection of CP stars in different galactic environments will help to understand their evolution and formation. The aim of this survey is to investigate the occurence of CP stars in open clusters depending on various parameters like age, metallicity and galactic location. Preliminary results have shown that the percentage of CP2 stars with ages between 30 and 100 Myr have two clear maxima, separated by a deep minimum. Therefore few of open clusters in this paper were selected within that age range to clarify this situation.Beside the detection of CP stars, we are able to determine cluster parameters like the age, ...

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“…With the established intrinsically consistent, empirical, effective temperature calibrations for B-type to mid F-type stars, it is now possible to study individual objects in very distant galactic open clusters (Paunzen et al 2005c) and extragalactic systems (Paunzen et al 2005a) for which, in general, no photometric data are available within a standard system.…”

Section: Introductionmentioning

confidence: 99%

An empirical temperature calibration for the $\Delta \textit{a}$ photometric system

Paunzen¹,

Schnell²,

Maitzen³

2006

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Context. With the ∆a photometric system, it is possible to study very distant galactic and even extragalactic clusters with a high level of accuracy. This can be done with a classical color-magnitude diagram and appropriate isochrones. The new calibration presented in this paper is a powerful extension.Aims. For open clusters, the reddening is straightforward for an estimation via Isochrone fitting and is needed in order to calculate the reddening-free, temperature sensitive, index (g 1 − y) 0 . As a last step, the calibration can be applied to individual stars. Methods. Because no a priori reddening-free photometric parameters are available for the investigated spectral range, we have applied the dereddening calibrations of the Strömgren uvbyβ system and compared them with extinction models for the Milky Way. As expected from the sample of bright stars, the extinction is negligible for almost all objects. As a next step, already established calibrations within the Strömgren uvbyβ, Geneva 7-color, and Johnson UBV systems were applied to a sample of 282 normal stars to derive a polynomial fit of the third degree for the averaged effective temperatures to the individual (g 1 − y) 0 values. Results. We derived an empirical temperature calibration for the ∆a photometric system for A-type to mid F-type with a mean of the error for the whole sample of ∆T eff is 134 K, which is lower than the value in Paper I for hotter stars. No statistically significant effect of the rotational velocity on the precision of the calibration was found. Conclusions. We have derived a new intrinsically consistent, empirical, effective temperature calibration for a spectral range from early B-type to mid F-type, luminosity class V to III stars within the photometric ∆a system. The statistical mean error over the complete spectral range of about 140 to 240 K will allow to individual objects of far distant galactic be studied as well as extragalactic clusters with high accuracy.

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CCD photometric search for peculiar stars in open clusters

Cited by 18 publications

References 23 publications

CCD photometric search for peculiar stars in open clusters

CCD photometric search for peculiar stars in open clusters

CCD photometric search for peculiar stars in open clusters

An empirical temperature calibration for the $\Delta \textit{a}$ photometric system

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