CCD photometric search for peculiar stars in open clusters - IV. Collinder 272, Pismis 20, Lynga° 14, NGC 6396 and NGC 6611

Autor(en)

Ernst Paunzen, Olga Pintado, Hans Michael Maitzen

Abstrakt

The time scale on which chemical peculiarity in upper main sequence stars begins is unknown. Results from the Hipparcos measurements indicate that the classical chemically peculiar (CP) stars occupy the whole area from the zero age main sequence to the terminal age main sequence (GoŽmez et al. 1998). However, Hubrig et al. (2000) reported that the magnetic fields appear only in stars that have already completed at least approximately 30% of their main sequence life time. Previous observations in the very young Orion OB1 and Scorpio-Centaurus associations (Joncas & Borra 1981; Borra et al. 1982) reveal a percentage of chemically peculiar stars that is significantly smaller (less than 5%) than that of the galactic field (up to 25%). This already indicates that the phenomenon needs at least several 106 yr to appear. Since no further observations have been published since then, we have observed the five very young (1 Myr = age = 25 Myr) open clusters Collinder 272, Pismis 20, Lynga° 14, NGC 6396 and NGC 6611. Photometry from 250 CCD frames in the three filter ?a-system results in very low detection limits (0.008 to 0.015 mag). We find no single photometrically chemically peculiar candidate in approximately 460 observed cluster members in the five program clusters. From the number of observed objects we deduce upper limits between 0.6% and 2.4% for the incidence of CP stars for the four observed aggregates.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

Universidad Nacional de Tucumán

Journal

Astronomy & Astrophysics

Band

395

Seiten

823-828

Anzahl der Seiten

6

ISSN

0004-6361

Publikationsdatum

2002

Peer-reviewed

Ja

ÖFOS 2012

103003 Astronomie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/1eb30ba5-466d-4388-a1f1-fe633620cbe7