NGC 663 as a laboratory for massive star evolution

Abstract

Massive young clusters with rich populations of high-mass stars are ideal laboratories to explore their evolutionary paths. Despite being the most prominent cluster in the Perseus-arm Cas OB8 association, NGC 663 remains comparatively little studied. We present a comprehensive investigation of its properties, integrating astrometric, photometric and spectroscopic data for the cluster and its surroundings, including accurate spectral classification for over 150 members. Gaia astrometry indicates over 300 B-type members, possibly rendering NGC 663 the most massive cluster in the Perseus arm, with initial mass likely exceeding 10000 M_\sun . This large population makes NGC 663 an excellent laboratory for studying massive star evolution. Spectral analysis of the earliest members reveals approximately solar metallicity and a turn-off mass of approximate 8.5 M_\sun, consistent with the photometric age of 23 Ma. We identify five spectroscopic blue stragglers, including the Be/X-ray binary RX J0146.9$+$6121. We outline its evolutionary history and compare its properties with other Be stars. Although the cluster contains many Be stars, their relative fraction is not particularly high. Intriguingly, four of the six blue supergiant members appear to have significantly higher masses than the brightest giants near the Hertzsprung gap. These observations suggest that most mid-B supergiants may form via mergers, unless stars of 10-12 M_\sun born as primaries in binaries rarely undergo supernova explosions. Similarly, if Be stars form through the binary channel, then either most are produced through case A evolution or supernovae are uncommon among primaries in this mass range.

Accepted for publication in MNRAS (17-JUL-2025), 44 Pages, 12 Figures and 12 Tables

References in corpus (66)

• Gaia Data Release 2. Summary of the contents and survey properties
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Evolution of asymptotic giant branch stars II. Optical to far-infrared isochrones with improved TP-AGB models
• Young massive star clusters
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones
• A Gaia DR2 view of the Open Cluster population in the Milky Way
• Formation of Double Neutron Star Systems
• Be/X-ray binaries
• Painting a portrait of the Galactic disc with its stellar clusters
• The Effects of Binary Evolution on the Dynamics of Core Collapse and Neutron-Star Kicks
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• Atmospheric NLTE-Models for the Spectroscopic Analysis of Blue Stars with Winds. II. Line-Blanketed Models
• Grids of stellar models with rotation - III. Models from 0.8 to 120 Msun at a metallicity Z = 0.002
• Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3
• Updated parameters of 1743 open clusters based on Gaia DR2
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• Clusters and mirages: cataloguing stellar aggregates in the Milky Way
• Massive runaways and walkaway stars
• The VLT-FLAMES Survey of Massive Stars: Observations centered on the Magellanic Cloud clusters NGC 330, NGC 346, NGC 2004, and the N11 region
• The Distribution of the Elements in the Galactic Disk III. A Reconsideration of Cepheids from l = 30 to 250 Degrees
• A New Class of High-Mass X-ray Binaries: Implications for Core Collapse and Neutron-Star Recoil
• Improving the open cluster census. III. Using cluster masses, radii, and dynamics to create a cleaned open cluster catalogue
• The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters
• The spectroscopic Hertzsprung-Russell diagram
• The spectroscopic Hertzsprung-Russell diagram of Galactic massive stars
• The Star Formation History and Mass Function of the Double Cluster h and Chi Persei
• ASteCA - Automated Stellar Cluster Analysis
• Two Populations of X-ray Pulsars Produced by Two Types of Supernovae
• Evolution of Mass Functions of Coeval Stars through Wind Mass Loss and Binary Interactions
• Apparent Age Spreads in Clusters and the Role of Stellar Rotation
• Be X-ray binaries in the SMC as indicators of mass transfer efficiency
• Populations of rotating stars II. Rapid rotators and their link to Be-type stars
• Investigating the lack of main-sequence companions to massive Be stars
• On the effect of rotation on populations of classical Cepheids I. Predictions at solar metallicity
• The dynamical evolution of Taurus--Auriga-type aggregates
• Spectral and spatial imaging of the Be+sdO binary phi Persei
• Validation of the accuracy and precision of Gaia EDR3 parallaxes with globular clusters
• Effects of close binary evolution on the main-sequence morphology of young star clusters
• The ARAUCARIA project: Grid-Based Quantitative Spectroscopic Study of Massive Blue Stars in NGC55
• Clues about the scarcity of stripped-envelope stars from the evolutionary state of the sdO+Be binary system phi Persei
• The IACOB project. VII. The rotational properties of Galactic massive O-type stars revisited
• The young massive SMC cluster NGC 330 seen by MUSE. I. Observations and stellar content
• Electron Capture Supernovae From Close Binary Systems
• On Rejuvenation in Massive Binary Systems
• The Single Star Path to Be Stars
• Rejuvenated accretors have less bound envelopes: Impact of Roche lobe overflow on subsequent common envelope events
• NGC 7419 as a template for red supergiant clusters
• Evidence for mass-dependent peculiar velocities in compact object binaries: Towards better constraints on natal kicks
• Oxygen, sulfur, and iron radial abundance gradients of classical Cepheids across the Galactic thin disk
• The IACOB project XII. A new grid of northern standards for the spectral classification of B-type stars
• Case A and B evolution towards electron capture supernova
• Westerlund 1 under the light of Gaia EDR3: Distance, isolation, extent, and a hidden population
• Photometric study of the double cluster h and chi Persei
• The initial spin distribution of B-type stars revealed by the split main sequences of young star clusters
• The IACOB project X. Large-scale quantitative spectroscopic analysis of Galactic luminous blue stars
• High-resolution spectroscopic study of massive blue and red supergiants in Per OB1
• Periodicities in the high-mass X-ray binary system RX J0146.9+6121/LS I+61 235
• Quiescent and active phases in Be stars: A WISE snapshot of young galactic open clusters
• Open clusters in AurOB2
• Cluster membership for the long period Cepheid calibrator SV Vul
• Searching for Be Stars in the Open Cluster NGC 663
• Stellar population astrophysics (SPA) with the TNG -- The chemical content of the red supergiant population in the Perseus complex
• Gaia colour-magnitude diagrams of young open clusters: Identification in the UBC catalogue and a comparison of manual and automated analysis

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