NGC 7419: An open cluster rich in Be stars

Pigulski, A.; Kopacki, G.

doi:10.1051/aas:2000281

Cited by 21 publications

(40 citation statements)

References 7 publications

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“…Thus, at present 31 Be-stars have been identified in the NGC 7419 cluster. These form about 36±7% of the entire star population of the cluster brighter than Rc = 16 m .1 [12].…”

Section: General Characteristics Of the Cluster Ngc 7419mentioning

confidence: 94%

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B and Be-stars in the young open stellar clusters NGC 659 and NGC 7419

Malchenko

Tarasov

2011

Astrophysics

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The populations of B and Be-stars in the young open clusters NGC 7419 and NGC 659 are studied. Lowresolution spectral observations in the region of the Hα line are used to study 34 members of NGC 7419 and additional spectra in the range λ3700-6200 Å are obtained for 12 stars. During the period of our observations, four previously identified Be-stars manifested an absorption profile for the Hα line. Emission in the Hα line is observed in the spectra of 21 objects. The members of the cluster NGC 7419 are classified as to spectral type. The position of the Be-stars on a two-color IR diagram and a comparison with the position of the objects in other clusters with similar ages cast doubt on the existence of two starformation waves. Moderate resolution spectra were obtained for 22 stars in the cluster NGC 659 over wavelengths of λ4050-5200 Å and for 7 objects in the neighborhood of the Hα line. Emission is observed in both the Hα and Hβ lines for two of the five Be-stars that were studied, while faint emission appears only in the Hα line in one of the stars. The other members of the cluster show no signs of emission in these spectra. T eff , log g, and Vsini are estimated for the observed stars. It is found that 5 of the objects are not members of the cluster.

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“…Thus, at present 31 Be-stars have been identified in the NGC 7419 cluster. These form about 36±7% of the entire star population of the cluster brighter than Rc = 16 m .1 [12].…”

Section: General Characteristics Of the Cluster Ngc 7419mentioning

confidence: 94%

“…11. Seventeen new Be-stars were discovered using narrow-band Hα photometry [12]. Thus, at present 31 Be-stars have been identified in the NGC 7419 cluster.…”

Section: General Characteristics Of the Cluster Ngc 7419mentioning

confidence: 99%

B and Be-stars in the young open stellar clusters NGC 659 and NGC 7419

Malchenko

Tarasov

2011

Astrophysics

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“…Their suggestion is based on the observation that on average the frequency of Be stars in clusters of nearly the same age steadily increases as the average metallicity decreases from the inner towards the outer regions of our galaxy, up to both Magellanic Clouds (MC). However, the low metallicity may not perhaps be the sole intervening factor to produce fast rotators and/or Be stars, because: a) within a radius of 500 pc near the Sun, the average rotation of BO-B4 type stars goes in the oposite direction to the above global tendency: it decreases from the inner to the outer regions of the Galaxy (Burki & Maeder 1977, Wolf et al 1982; b) the frequency of field Be stars in the MC is about the same as that of Galactic field Be stars (Keller et al 1999); c) due to discrepancies in the estimates according to authors and methods, the fractions of Be stars earlier than B4 in the most populous clusters in Be stars in the Galaxy and in the MC (average age 21 ± 7 Myr), do not reveal strong dependence on metallicity: (SMC) 48% NGC 330 (Grebel 1997, Keller et al 1999); (LMC) 33% NGC 2100, 27% NGC 1818 (Keller et al 1999); (Galaxy) 36% NGC 7419 (Pigulski & Kopacki 2000); 31% NGC 663 (Pigulski et al 2001); 36% NGC 3766 (Shobbrook 1987); 25-50% NGC 869/884 (Waelkens et al 1990). …”

Section: Single Starsmentioning

confidence: 96%

Rotation and Properties of Be Stars

Zorec¹

2004

Symp. - Int. Astron. Union

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Abstract. The actual characteristic average surface angular velocity ratio of the Be phenomenon may be higher than nine = 0.8 ± 0.1 derived from vsini values not corrected from gravity darkening effects. Late Be stars need not only higher values of nine, but also larger main sequence age ratios TITMs than early Be stars to display the Be phenomenon. Galactic field Be stars appear at any MS phase, but their frequency is higher for T / TMS ;(j 0.5. Be stars are probably neat differential rotators, i.e. they rotate with energy ratios kinetic/jgravitational] larger than withstood by critical rigid rotators. Initial formation conditions must favor the existence of fast rotators, while only a small fraction of them could be accounted for by mass transfer in close binary systems. Bn stars could perhaps represent a pre-Be phase.

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“…However, in the Galaxy this percentage can change according to the local physical conditions, mainly chemical composition (Maeder et al 1999), and/or properties of the environment, in particular clusters, streams, and associations, where the percentage of Be stars depends on cluster age (Fabregat & Torrejón 2000 (Mathew et al 2008) or approaching 30% in NGC 663 and NGC 7419 (Pigulski & Kopacki 2000;Pigulski et al 2001). Nevertheless, the percentages of Be stars are underestimated because the Be phases are not permanent and detection of the Be phenomenon with slitless spectroscopy or photometry is not complete, since stars with very faint emission characteristics cannot be identified The small red points are the targets observed with the satellite (19 878 objects), which clearly depict a magnitude limited sample (11 V obs 17 mag).…”

Section: Anticenter Direction: Lra1 and Ir1 Exofieldsmentioning

confidence: 99%

Study of a sample of faint Be stars in the exofield of CoRoT

Semaan

Hubert

Zorec

et al. 2013

A&A

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Context. Be stars are probably the most rapid rotators among stars in the main sequence (MS) and, as such, are excellent candidates to study the incidence of the rotation on the characteristics of their non-radial pulsations, as well as on their internal structure. Pulsations are also thought to be possible mechanisms that help the mass ejection needed to build up the circumstellar disks of Be stars. Aims. The purpose of this paper is to identify a number of faint Be stars observed with the CoRoT satellite and to determine their fundamental parameters, which will enable us to study their pulsation properties as a function of the location in the HR diagram and to search for correlations with the light outbursts, which are possibly produced by discrete mass ejections. Methods. We identified those objects in the exofields of CoRoT presenting the Be phenomenon using Hα surveys, as well as automated methods based on pulsation properties that we finally confirmed with FLAMES/GIRAFFE and X-shooter spectroscopic observations at VLT/ESO, and with near-IR photometry. The spectra were 1) corrected for the veiling effect, 2) treated with the GIRFIT code to determine apparent fundamental parameters, and 3) corrected with the FASTROT code for effects induced by the rapid rotation. Results. A list of 41 Be star candidates were found from photometric and spectroscopic criteria. The spectral coverage useful for determining the fundamental parameters was obtained for only about half of them. We then spectroscopically identified 21 Be stars, two probable Be stars, and two B stars contaminated by the Sh 2-284 nebulosity. A short description of the spectral characteristics of each star is given. The fundamental parameters and, in particular, the rotation frequency ν r (cycles per day) were all corrected for rotational effects at rotation rates ranging from Ω/Ω c = 0.8 to 1.0. We have determined the positions of Be stars in the HR diagram and find two of them located beyond the MS phase. Conclusions. The well-determined fundamental parameters presented in this paper for a statistically reliable sample of Be stars will enable us in forthcoming papers to compare the properties of stars as pulsators either according to their location in different regions of the HR diagram or with those predicted from theory.

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NGC 7419: An open cluster rich in Be stars

Cited by 21 publications

References 7 publications

B and Be-stars in the young open stellar clusters NGC 659 and NGC 7419

B and Be-stars in the young open stellar clusters NGC 659 and NGC 7419

Rotation and Properties of Be Stars

Study of a sample of faint Be stars in the exofield of CoRoT

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