Extended main-sequence turnoffs in the double cluster $h$ and $\chi$ Persei: The complex role of stellar rotation

Abstract

Using {\sl Gaia} Data Release 2 photometry, we report the detection of extended main-sequence turnoff (eMSTO) regions in the color--magnitude diagrams (CMDs) of the $\sim 14$ Myr-old double clusters $h$ and $\chi$ Persei (NGC 869 and NGC 884). We find that stars with masses below $\sim$1.3 $M_{\odot }$ in both $h$ and $\chi$ Persei populate narrow main sequences (MSs), while more massive stars define the eMSTO, closely mimicking observations of young Galactic and Magellanic Cloud clusters (with ages older than $\sim$30 Myr). Previous studies based on clusters older than $\sim$30 Myr find that rapidly rotating MS stars are redder than slow rotators of similar luminosity, suggesting that stellar rotation may be the main driver of the eMSTO. By combining photometry and projected rotational velocities from the literature of stars in $h$ and $\chi$ Persei, we find no obvious relation between the rotational velocities and colors of non-emission-line eMSTO stars, in contrast with what is observed in older clusters. Similarly to what is observed in Magellanic Cloud clusters, most of the extremely rapidly rotating stars, identified by their strong H$\alpha$ emission lines, are located in the red part of the eMSTOs. This indicates that stellar rotation plays a role in the color and magnitude distribution of MSTO stars. By comparing the observations with simulated CMDs, we find that a simple population composed of coeval stars that span a wide range of rotation rates is unable to reproduce the color spread of the clusters' MSs. We suggest that variable stars, binary interactions, and stellar rotation affect the eMSTO morphology of these very young clusters.

14 pages, 12 figures, ApJ accepted

References in corpus (46)

• Gaia Data Release 2. Summary of the contents and survey properties
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• The evolution of rotating stars
• Gaia Data Release 2: Photometric content and validation
• Global survey of star clusters in the Milky Way II. The catalogue of basic parameters
• A Gaia DR2 view of the Open Cluster population in the Milky Way
• Grids of stellar models with rotation - III. Models from 0.8 to 120 Msun at a metallicity Z = 0.002
• Gravity darkening in rotating stars
• A Stellar Rotation Census of B Stars: from ZAMS to TAMS
• The Effect of Stellar Rotation on Colour-Magnitude Diagrams: On the apparent presence of multiple populations in intermediate age stellar clusters
• A double main sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud
• The Age and Age Spread of the Praesepe and Hyades Clusters: a Consistent, ~800 Myr Picture from Rotating Stellar Models
• Stellar Rotation in Young Clusters. I. Evolution of Projected Rotational Velocity Distributions
• The Star Formation History and Mass Function of the Double Cluster h and Chi Persei
• The orbits of open clusters in the Galaxy
• Multiple stellar populations in Magellanic Cloud clusters. VI. A survey of multiple sequences and Be stars in young clusters
• Populations of rotating stars III. SYCLIST, the new Geneva Population Synthesis code
• The Stellar Population of h and chi Persei: Cluster Properties, Membership, and the Intrinsic Colors and Temperatures of Stars
• Extended main sequence turnoff as a common feature of Milky Way open clusters
• Apparent Age Spreads in Clusters and the Role of Stellar Rotation
• Multiple stellar populations in Magellanic Cloud clusters. III. The first evidence of an extended main sequence turn-off in a young cluster: NGC1856
• Multiple stellar populations in Magellanic Cloud clusters. IV. The double main sequence of the young cluster NGC1755
• Nitrogen abundances and multiple stellar populations in the globular clusters of the Fornax dSph
• Rotating Stellar Models Can Account for the Extended Main Sequence Turnoffs in Intermediate Age Clusters
• Extended Main Sequence Turnoffs in Open Clusters as Seen by Gaia: I. NGC 2818 and the Role of Stellar Rotation
• NGC 1866: First Spectroscopic Detection of Fast Rotating Stars in a Young LMC Cluster
• Discovery of extended main sequence turn offs in Galactic open clusters
• Different stellar rotation in the two main sequences of the young globular cluster NGC1818: first direct spectroscopic evidence
• Stars caught in the braking stage in young Magellanic Clouds clusters
• The exclusion of a significant range of ages in a massive star cluster
• Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters: Stellar Rotation diminishes, but does not eliminate, Age Spreads
• Discovery of Extended Main Sequence Turn-offs in Four Young Massive Clusters in the Magellanic Clouds
• The Contributions of Interactive Binary Stars to Double Main Sequence Turn-Offs and Dual Red Clump of Intermediate-Age Star Clusters
• Photometric multi-site campaign on the open cluster NGC 884 I. Detection of the variable stars
• The Minimum Mass of Rotating Main Sequence Stars and its Impact on the Nature of Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters in the Magellanic Clouds
• Observational hints of a real age spread in the young LMC star cluster NGC 1971
• The effects of the overshooting of the convective core on main-sequence turnoffs of young- and intermediate-age star clusters
• Stellar variability at the main-sequence turnoff of the intermediate-age LMC cluster NGC 1846
• The Effects of Binary Stars on the Color-Magnitude Diagrams of Young-Age Massive Star Clusters
• Pulsating B-type stars in the young open cluster h Persei (NGC 869)

Cited by in corpus (29)

• Painting a portrait of the Galactic disc with its stellar clusters
• Probing the interior physics of stars through asteroseismology
• Internal mixing of rotating stars inferred from dipole gravity modes
• 3D Morphology of Open Clusters in the Solar Neighborhood with Gaia EDR3: its Relation to Cluster Dynamics
• Stellar mergers as the origin of the blue main-sequence band in young star clusters
• Effects of close binary evolution on the main-sequence morphology of young star clusters
• Hunting for Neighboring Open Clusters with Gaia DR3: 101 New Open Clusters within 500 pc
• Unveiling hidden stellar aggregates in the Milky Way: 1656 new star clusters found in Gaia EDR3
• Gaia-ESO Survey: Role of magnetic activity and starspots on pre-main sequence lithium evolution
• Isochrone-cloud fitting of the extended Main-Sequence Turn-Off of young clusters
• First phase space portrait of a hierarchical stellar structure in the Milky Way
• Asteroseismology of the young open cluster NGC 2516 I: Photometric and spectroscopic observations
• The effect of the centrifugal acceleration on period spacings of gravito-inertial modes in intermediate-mass stars
• High-resolution spectroscopic study of massive blue and red supergiants in Per OB1
• Ongoing hierarchical massive cluster assembly: the LISCA II structure in the Perseus complex
• Stellar Population Astrophysics (SPA) with the TNG: Stock 2, a little-studied open cluster with an eMSTO
• The role of binarity and stellar rotation in the split main sequence of NGC 2422
• Hubble Space Telescope survey of Magellanic Cloud star clusters. UV-dim stars in young clusters
• The extended Main-Sequence Turnoff of the Milky Way open cluster Collinder 347
• On the origin of the split main sequences of the young massive cluster NGC 1856
• The Gaia-ESO survey: A spectroscopic study of the young open cluster NGC 3293
• On aging star clusters using red supergiants independent of the fraction of interacting binary stars
• Unveiling the Hierarchical Structure of Open Star Clusters: the Perseus Double Cluster
• At what mass are stars braked? The implication from the turnoff morphology of NGC 6819
• UVIT-HST-Gaia-VISTA study of KRON 3 in the Small Magellanic Cloud: A cluster with an extended red clump in UV
• Extended Main Sequences in Star Clusters
• LAMOST medium-resolution spectroscopic survey of Galactic Open Clusters (LAMOST-MRS-O): An overview of survey plan and preliminary results
• The Predicted Properties of Helium-Enriched Globular Cluster Progenitors at High Redshift
• Quantifying Systematic Age Discrepancies in Very Young Star Clusters