Yellow evolved stars in open clusters

Sowell, James R.

doi:10.1086/191196

Cited by 19 publications

(17 citation statements)

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“…We are able to confirm the variable stars in common a detailed analysis of those objects will be published elsewhere. Chopinet (1956) classified WEBDA #1 as A1 Ia p, but other sources list B9 Iab (Hiltner 1956), B8 Ia (Sowell 1987) and B8 I (Massey et al 1995). Because this object has a V magnitude of 8.8, we were not able to measure a ∆a index.…”

Section: Resultsmentioning

confidence: 99%

CCD photometric search for peculiar stars in open clusters

Paunzen¹,

Netopil²,

Iliev

et al. 2005

A&A

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In a sample of six young open clusters (NGC 1502, NGC 3105, Stock 16, NGC 6268, NGC 7235, and NGC 7510) we investigated 1753 objects using the narrow band, three filter ∆a photometric system resulting in the detection of eleven bona-fide magnetic chemically peculiar (CP) stars and five Be or metal-weak stars. The results for the distant cluster NGC 3105 is most important because of the still unknown influence of the global metallicity gradient of the Milky Way. These findings confirm that CP stars are present in open clusters of very young ages (log t ≥ 6.90) at galactocentric distances up to 11.4 kpc. For all programme clusters the age, reddening, and distance modulus were derived using the corresponding isochrones. Some additional variable stars within Stock 16 could be identified by comparing different photometric studies.

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Section: Resultsmentioning

confidence: 99%

CCD photometric search for peculiar stars in open clusters

Paunzen¹,

Netopil²,

Iliev

et al. 2005

A&A

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“…In total ten peculiar objects were found (see Table 2) among possible members according to their location within the color−magnitude diagram or the investigation by Fünfschilling (1967). The evolved stars #32 (−42) and 129 (−46), showing a possible emission, were investigated spectroscopically by Sowell (1987), classified as G0/5 III/V and F2 Ib, respectively. The object #32 was determined as a possible foreground star and #129 showed an increase in brightness in the B and V passbands of 0.2 to 0.3 mag during a period of ninety days, however #129 is a double star according to Mason et al (2002).…”

Section: Resultsmentioning

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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“…He classified HD 9365 as F1 V and also concluded that one of the other two components in the system, an F9 V star that is 1.5 mag fainter and 44 00 away, is a physical companion. Additional spectral classifications of HD 9365 are similar: A9 V (Sowell 1987), F0 V (Jensen 1981), and F1 dwarf .…”

Section: Criteria For Confirming Doradus Variabilitymentioning

confidence: 91%

Photometry and Spectroscopy of 11 γ Doradus Stars

2007

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We have used precise photometric and high-dispersion spectroscopic observations to study 11 Doradus stars, 10 of them newly confirmed. Only five of these 11 Doradus stars appear to be single; two are primaries of double-lined spectroscopic binaries, one is the secondary of a double-lined binary, two are primaries of visual binaries and, in the case of the double-lined binary (HD 86371), either or both components could be a pulsating Doradus star. We have determined a preliminary orbital period of 5.32 days for the double-lined binary HD 41547. Several of the stars show spectroscopic lineYprofile and low-amplitude radial velocity variability indicative of pulsation. All 11 stars are photometrically variable with amplitudes between 4 and 94 mmag in Johnson B and periods between 0.38 and 1.86 days. The 11 stars have between two and five independent periods. The variability at all periods approximates a sinusoid. We provide a new tabulation of all 66 Doradus stars confirmed to date and list some of their properties. All are dwarfs or subgiants and lie within a well-defined region of the H-R diagram that overlaps the cool edge of the Scuti instability strip. Four of the new Doradus variables from this paper also lie within the Scuti instability strip but do not exhibit the additional higher frequency variability typical of Scuti stars. Among the 66 confirmed Doradus variables, we find no correlation between the period of the strongest pulsation mode and the (B À V ) color index, absolute magnitude, or luminosity.

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Yellow evolved stars in open clusters

Cited by 19 publications

References 0 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

Photometry and Spectroscopy of 11 γ Doradus Stars

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