NGC 7419 as a template for red supergiant clusters

Abstract

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. 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. 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. 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 $M_{\sun}$ in B stars at present. Extrapolating this to lower masses indicates an initial cluster mass of between 7000 and 10000 Msolar, 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. 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.

Tables 3,4 and 7 will be published electronically Accepted for publication in Astronomy and Astrophysics

References in corpus (12)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• Effects of gravitational darkening on the determination of fundamental parameters in fast rotating B-type stars
• A massive cluster of Red Supergiants at the base of the Scutum-Crux arm
• Discovery of an Extraordinarily Massive Cluster of Red Supergiants
• The 3D Morphology of VY Canis Majoris. I The Kinematics of the Ejecta
• A third red supergiant rich cluster in the Scutum-Crux Arm
• Fundamental properties and atmospheric structure of the red supergiant VY CMa based on VLTI/AMBER spectro-interferometry
• Red supergiants around the obscured open cluster Stephenson 2
• Imaging the Cool Hypergiant NML Cygni's Dusty Circumstellar Envelope with Adaptive Optics
• NGC 7419: A young open cluster with a number of very young intermediate mass pre-MS stars
• Multi-wavelength study of a young open cluster NGC 7419
• Towards ensemble asteroseismology of the young open clusters Chi Persei and NGC 6910

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