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

Malchenko, S. L.; Tarasov, A. E.

doi:10.1007/s10511-011-9157-x

Cited by 4 publications

(8 citation statements)

References 18 publications

(34 reference statements)

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“…4) shows no characteristics that allow its classification as a Be star. Hα was still weakly in emission in 2006 (Malchenko & Tarasov 2011). A similar evolution was followed by Star 151.…”

Section: Be Starssupporting

confidence: 57%

“…This high fraction of Be stars has been confirmed by Subramanian et al (2006) using slitless spectroscopy and by Joshi et al (2008) using Hα photometry. Malchenko & Tarasov (2011) obtained intermediate-resolution spectroscopy around the Hα line for most of the candidate Be stars, confirming their nature.…”

Section: Introductionmentioning

confidence: 63%

“…They remarked that the Paschen lines were flat-bottomed, an effect that they attributed to weak Be characteristics, but that could also be due to the presence of two stellar spectra. Malchenko & Tarasov (2011) observed weak double-peaked Hα in this object in June 2006.…”

Section: Spectral Classificationmentioning

confidence: 76%

“…After this, it was not detected in emission in 2004 or 2005, but reappeared as an emission-line star in the 2008 slitless spectrum. Malchenko & Tarasov (2011) had already detected a very weak double-peaked emission in 2006. In November 2010, it displayed a moderately strong double-peaked emission line (Fig.…”

Section: Be Starsmentioning

confidence: 99%

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NGC 7419 as a template for red supergiant clusters

Marco

Negueruela

2013

A&A

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Context. The open cluster NGC 7419 is known to contain five red supergiants and a very high number of Be stars. However, there are conflicting reports about its age and distance that prevent a useful comparison with other clusters. Aims. We intend to obtain more accurate parameters for NGC 7419, using techniques different from those of previous authors, so that it may be used as a calibrator for more obscured clusters. Methods. We obtained Strömgren photometry of the open cluster NGC 7419, as well as classification spectroscopy of ∼20 stars in the area. We then applied standard analysis and classification techniques. Results. We find a distance of 4 ± 0.4 kpc and an age of 14 ± 2 Myr for NGC 7419. The main-sequence turn-off is found at spectral type B1, in excellent agreement. We identify 179 B-type members, implying that there are more than 1200 M in B stars at present. Extrapolating this to lower masses indicates an initial cluster mass of between 7000 and 10 000 M , depending on the shape of the initial mass function. We find a very high fraction (≈40%) of Be stars around the turn-off, but very few Be stars at lower masses. We also report for the first time a strong variability in the emission characteristics of Be stars. We verified that the parameters of the red supergiant members can be used to obtain accurate cluster parameters. Conclusions. NGC 7419 is sufficiently massive to serve as a testbed for theoretical predictions and as a template to compare more obscured clusters. The distribution of stars above the main-sequence turn-off is difficult to accommodate with current evolutionary tracks. Though the presence of five red supergiants is marginally consistent with theoretical expectations, the high number of Be stars and very low number of luminous evolved B stars hint at some unknown physical factor that is not considered in current synthesis models.

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“…4) shows no characteristics that allow its classification as a Be star. Hα was still weakly in emission in 2006 (Malchenko & Tarasov 2011). A similar evolution was followed by Star 151.…”

Section: Be Starssupporting

confidence: 57%

Section: Introductionmentioning

confidence: 63%

Section: Spectral Classificationmentioning

confidence: 76%

Section: Be Starsmentioning

confidence: 99%

See 2 more Smart Citations

NGC 7419 as a template for red supergiant clusters

Marco

Negueruela

2013

A&A

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“…We considered at least 60% of the Be stars in NGC 869 and NGC 884, NGC 6913, and NGC 7419 and took the spectra of all Be stars in NGC 457, NGC 659, NGC 6871, and Berkeley 86. The results of our analysis of the relative content of early-type Be stars in the clusters studied are presented in Malchenko and Tarasov (2008, 2009, 2011, Malchenko (2008), and Table 1.…”

Section: Introductionmentioning

confidence: 99%

Relative content of Be stars in young open star clusters

Tarasov

Malchenko

2012

Astron. Lett.

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Based on high-and medium-resolution spectra, we analyze the population of Be stars in eight young open star clusters. We have found a clear dependence of the relative content of early-type (B0-B3) Be stars on the cluster age. The relative concentration of Be stars of spectral types B0-B3 gradually increases with cluster age, reaching its maximum value of 0.46 in clusters with ages of 12-20 Myr. The almost complete absence of Be stars in older clusters can be easily explained by the fact that B stars leave the main sequence. The few emission objects in clusters with ages of 1-7 Myr are most likely Herbig Be stars. Such a distribution of Be stars in clusters unequivocally points to the evolutionary status of the Be phenomenon. We also briefly consider the causes of this pattern.

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Be Stars in Open Stellar Clusters

Tarasov

2017

Astrophysics

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

Cited by 4 publications

References 18 publications

NGC 7419 as a template for red supergiant clusters

NGC 7419 as a template for red supergiant clusters

Relative content of Be stars in young open star clusters

Be Stars in Open Stellar Clusters

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