CCD photometric search for peculiar stars in open clusters

Abstract. In total, more than 550 objects within the fields of five open clusters were investigated in order to find classical chemically peculiar stars. One bona-fide CP candidate was detected in each of the open clusters NGC 3960, NGC 6192 and NGC 6451. All three objects seem to be members of the corresponding cluster, taking the results from our photometry as well as from the literature. For NGC 6192 and NGC 6451 we found widely different interstellar reddening values and therefore distances and ages in the literature. From an analysis of published Johnson UBV RI photometry, we were able to rule out a rather old age for NGC 6451. This is also supported by the finding of one peculiar object in this cluster with spectral type of about A2. Five variable objects within the field of NGC 6134 were detected. The variability exceeds 10 times (or typically 0.03 mag) the standard deviation of the weighted individual measurements. But since our observations were obtained mostly within one hour (typical integration times of five minutes per filter) on several nights within 45 days, no light curves could be derived. For this cluster, some Am candidates were reported for which we were not able to detect a significant positive ∆a-value.

show abstract

“…Two previous papers (Bayer et al 2000;Paunzen & Maitzen 2001) have already shown the high efficiency of this system.…”

Section: Introductionmentioning

confidence: 66%

CCD photometric search for peculiar stars in open clusters

Paunzen

Maitzen

2002

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The ∆a-photometry was obtained in a program including four other open clusters (see Bayer et al 2000). The Bochum 61 cm telescope at ESO and the Helen-Sawyer-Hogg 61 cm telescope at UTSO (Las Campanas) were used with CCD cameras with a field of view around 4 arcmin.…”

Section: The Observationsmentioning

confidence: 99%

Rotation of stars in NGC 6134

Rasmussen¹,

Bruntt²,

Frandsen³

et al. 2002

A&A

Self Cite

View full text Add to dashboard Cite

Abstract. We present results of spectroscopic observations of selected stars in the southern open cluster NGC 6134. We have determined the rotational velocities of the six known δ Scuti stars in NGC 6134 as well as several other non-variable stars with similar colour temperature in order to investigate if v sin i and variability is somehow connected: we find no such correlation. We also compare the distribution of v sin i of δ Scuti stars and non-variable stars with four other well-studied open clusters to look for any systematic behaviour, but we find no conclusive evidence for v sin i and variability to be connected. We have also used the spectra to carry out an abundance analysis of the δ Scuti stars in NGC 6134 to confirm the high metal content of the cluster. We find [Fe/H] = +0.38 ± 0.05 which is in agreement with the result obtained from Strömgren photometry. We also present ∆a photometry of the cluster, but we find no chemical peculiar stars based on this index.

show abstract

“…The normality line (see Bayer et al 2000 for the definition) is shifted by E(g 1 − y) = 0.4E(B − V) to the red and by a small amount E(a) to higher a-values (Maitzen 1993) …”

Section: Observations Reduction and Resultsmentioning

confidence: 99%

“…The first three papers of this series (Bayer et al 2000;Paunzen & Maitzen 2001, 2002 Joncas & Borra (1981) and Borra et al (1982) presented ∆a-photometry for the Orion OB1 and Scorpio-Centaurus associations. They concluded that the metal enrichment takes place on time scales of a few 10 7 yr with an incidence of CP stars less than 5% of all stars in the relevant temperature domain.…”

Section: Introductionmentioning

confidence: 99%

CCD photometric search for peculiar stars in open clusters

Paunzen

Pintado

Maitzen

2002

A&A

Self Cite

View full text Add to dashboard Cite

Abstract. 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 (Gómez 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 10 6 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, Lyngå 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.

show abstract

CCD photometric search for peculiar stars in open clusters

Cited by 18 publications

References 11 publications

CCD photometric search for peculiar stars in open clusters

CCD photometric search for peculiar stars in open clusters

Rotation of stars in NGC 6134

CCD photometric search for peculiar stars in open clusters

Contact Info

Product

Resources

About