Theoretical isochrones for the Delta a photometric system

Abstract

We have calculated theoretical isochrones for the photometric Delta a system to derive astrophysical parameters such as the age, reddening and distance modulus for open clusters. The Delta a system samples the flux depression at 520 nm which is highly efficient to detect chemically peculiar (CP) objects of the upper main sequence. The evolutionary status of CP stars is still a matter of debate and very important to test, for example, the dynamo and diffusion theories. In fact, the dynamo or fossil origin of the magnetic fields present in this kind of stars it still not clear. Using the stellar evolutionary models by Claret (1995), a grid of isochrones with different initial chemical compositions for the Delta a system was generated. The published data of 23 open clusters were used to fit these isochrones with astrophysical parameters (age, reddening and distance modulus) from the literature. As an additional test, isochrones with the same parameters for Johnson UBV data of these open clusters were also considered. The fits show a good agreement between the observations and the theoretical grid. We find that the accuracy of fitting isochrones to Delta a data without the knowledge of the cluster parameters is between 5 and 15%.

5 pages, 4 figures, accepted by A&A

References in corpus (2)

• The 5200A flux depression of chemically peculiar stars: I. Synthetic Delta a photometry - the normality line
• On the evolutionary status of chemically peculiar stars of the upper main sequence

Cited by in corpus (11)

• On the detection of chemically peculiar stars using Delta a photometry
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• Asiago eclipsing binaries program. III. V570 Per
• An empirical temperature calibration for the Delta a photometric system. I. The B-type stars
• CCD photometric search for peculiar stars in open clusters. VI. NGC 1502, NGC 3105, Stock 16, NGC 6268, NGC 7235 and NGC 7510
• CCD photometric search for peculiar stars in open clusters. VII. Berkeley 11, Berkeley 94, Haffner 15, Lynga 1, NGC 6031, NGC 6405, NGC 6834 and Ruprecht 130
• Asiago eclipsing binaries program. II. V505 Per
• CCD $UBV(RI{)}_C$ Photometry of Twenty Open Clusters
• CCD-Delta a and BVR photometry of NGC 7296
• On the incidence of chemically peculiar stars in the Large Magellanic cloud
• Chemically peculiar stars in the Large Magellanic Cloud