Exploring membership and variability in NGC 7419: an open cluster rich in supergiants and Be type stars

ABSTRACT NGC 7419 is a young open cluster notable for hosting five red supergiants and a high abundance of Classical Be (CBe) stars. CBe stars are main-sequence non-supergiant B-type stars that exhibit or have exhibited Balmer-line emissions in their spectra. We perform a membership analysis using Gaia DR3 data and machine learning techniques like Gaussian mixture models and Random Forest and determine the cluster’s mean distance to be ${3.6^{+1.0}_{-0.6}}$ kpc. We identify 499 Gaia-based members with a mass above $\sim$1.2 M$_\odot$, and estimate the cluster’s age to be $21.1 ^{+1.6}_{-0.6}$ Myr. Using our revised H α excess-based analysis, we find 42 CBe stars containing many known CBe stars, bringing the total number of CBe stars in NGC 7419 to 49 and the fraction of CBe to (B + CBe) members to 12.7 per cent. We investigate the variability of the candidate members from Zwicky Transient Facility and NEOWISE data using standard deviation, median absolute deviation, and Stetson index (J), and their periodicity using the Generalized Lomb–Scargle periodogram variability. We find that 66 per cent of CBe stars are variable: 23 per cent show periodic signals, typical of pulsation/rotation, 41 per cent display variability characteristic of disc dynamics or binarity, and 14 per cent exhibit long-term changes, consistent with disc dissipation/formation. We also find that all pulsating CBe stars are early-type, while 50 per cent of stars with long-term variations are early-type, and the other 50 per cent are mid-type. Our results agree with previous findings in the literature and confirm that CBe stars display variability through multiple mechanisms across different time-scales.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-07-05
DOI
https://doi.org/10.1093/mnras/staf1104
Citations
2
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
2.31

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article

Exploring membership and variability in NGC 7419: an open cluster rich in supergiants and Be type stars

A. C. Carciofi, Jessy Jose, Arghya Chakraborty
2 citations
Monthly Notices of the Royal Astronomical Society
Stellar, planetary, and galactic studies
2.31
article

Exploring membership and variability in NGC 7419: an open cluster rich in supergiants and Be type stars

A. C. Carciofi, Jessy Jose, Arghya Chakraborty
article en
2 citations

Abstract

ABSTRACT NGC 7419 is a young open cluster notable for hosting five red supergiants and a high abundance of Classical Be (CBe) stars. CBe stars are main-sequence non-supergiant B-type stars that exhibit or have exhibited Balmer-line emissions in their spectra. We perform a membership analysis using Gaia DR3 data and machine learning techniques like Gaussian mixture models and Random Forest and determine the cluster’s mean distance to be ${3.6^{+1.0}_{-0.6}}$ kpc. We identify 499 Gaia-based members with a mass above $\sim$1.2 M$_\odot$, and estimate the cluster’s age to be $21.1 ^{+1.6}_{-0.6}$ Myr. Using our revised H α excess-based analysis, we find 42 CBe stars containing many known CBe stars, bringing the total number of CBe stars in NGC 7419 to 49 and the fraction of CBe to (B + CBe) members to 12.7 per cent. We investigate the variability of the candidate members from Zwicky Transient Facility and NEOWISE data using standard deviation, median absolute deviation, and Stetson index (J), and their periodicity using the Generalized Lomb–Scargle periodogram variability. We find that 66 per cent of CBe stars are variable: 23 per cent show periodic signals, typical of pulsation/rotation, 41 per cent display variability characteristic of disc dynamics or binarity, and 14 per cent exhibit long-term changes, consistent with disc dissipation/formation. We also find that all pulsating CBe stars are early-type, while 50 per cent of stars with long-term variations are early-type, and the other 50 per cent are mid-type. Our results agree with previous findings in the literature and confirm that CBe stars display variability through multiple mechanisms across different time-scales.

Monthly Notices of the Royal Astronomical SocietyVol. 541(2)
Universidade de São Paulo (BR), Indian Institute of Technology Tirupati (IN), Indian Institute of Science Education and Research, Tirupati (IN), Instituto de Geofísica y Astronomía (CU)
National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Ohio State University, California Institute of Technology, Harvard University, University of Utah, University of Washington, Johns Hopkins University, University of Virginia, New Mexico State University, University of Illinois System, Space Telescope Science Institute, European Space Agency, Flatiron Health, University of Hertfordshire, Department of Science and Technology, Republic of South Africa, Department of Science and Technology, Ministry of Science and Technology, India, École Polytechnique Fédérale de Lausanne, Fundação de Amparo à Pesquisa do Estado de São Paulo, University of Toronto, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Universidad Nacional Autónoma de México, Yunnan University, Nanjing University, Stockholms Universitet, China National Textile and Apparel Council, Leibniz-Institut für Astrophysik Potsdam, Max-Planck-Institut für Astronomie, University of Illinois at Urbana-Champaign, Jet Propulsion Laboratory, University of California, Los Angeles, University of Colorado Boulder, Smithsonian Astrophysical Observatory, Science and Technology Facilities Council, Deutsches Elektronen-Synchrotron, Leibniz-Gemeinschaft, Science and Engineering Research Board, National Astronomical Observatories, Chinese Academy of Sciences, Planetary Science Division
Openalex Percentile: Top 11%
Stellar, planetary, and galactic studies
2.31
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