J/MNRAS/542/703ivo://CDS.VizieR/J/MNRAS/542/703doi:10.26093/cds/vizier/bg-gy-nzCDSMarco A.Negueruela I.Castro N.Simon-diaz S.2026-08-03T07:33:35Z2025-09-26T11:16:35ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fropen-star-clustersinfrared-photometryvisible-astronomybroad-band-photometryextinctionMassive 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 10^4^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 ~8.5M_{sun}_, consistent with the photometric age of 23Ma. 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 10-12M_{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.2025MNRAS.542..703Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/542/703CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/A+A/376/144 : BV(RI)_C_H{alpha} photometry of NGC 663 (Pigulski+, 2001)J/MNRAS/358/66 : uvby{beta} photometry of NGC 663 (Fabregat+, 2005)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/542/703https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/542/703http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/542/703https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/542/703https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/542/703http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/542/703GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/542/703/table2 (Basic parameters for BSG stars in the area of NGC 663 that were observed with FIES)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/542/703/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/542/703/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/542/703/table2?GETtext/xml+votable180.050000true26.64387561.26250.005555555555555556Cone search capability for table J/MNRAS/542/703/tablea1 (Stars with spectra observed with the INT at R=4000. Parallaxes have been zero-point corrected)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/542/703/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/542/703/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/542/703/tablea1?GETtext/xml+votable180.050000true26.47387561.32055560.005555555555555556Cone search capability for table J/MNRAS/542/703/tablea2 (Stars with spectra observed with the INT only at R=1400. Parallaxes have been zero-point corrected)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/542/703/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/542/703/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/542/703/tablea2?GETtext/xml+votable180.050000true26.690291761.50255560.005555555555555556Cone search capability for table J/MNRAS/542/703/tablea3 (Stars with spectra taken with the OHP (R=900) only. Parallaxes have been zero-point corrected)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/542/703/tablea3?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/542/703/tablea3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/542/703/tablea3?GETtext/xml+votable180.050000true26.532791761.15530560.005555555555555556Cone search capability for table J/MNRAS/542/703/tableb1 (Coordinates in J2000, ubvy{beta} photometry, and spectral types for Gaia members)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/542/703/tableb1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/542/703/tableb1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/542/703/tableb1?GETtext/xml+votable180.050000true26.49037561.15383330.005555555555555556Cone search capability for table J/MNRAS/542/703/tableb2 (Coordinates in J2000 and photometric values in E(b-y), Ec1, c0, V0 and MV for Gaia members in NGC 663)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/542/703/tableb2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/542/703/tableb2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/542/703/tableb2?GETtext/xml+votable180.050000true26.49037561.15383330.0055555555555555566/3610 3632https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/542/703?format=asciiOpticalInfrareddefaultJ/MNRAS/542/703/table2Basic parameters for BSG stars in the area of NGC 663 that were observed with FIESrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainWEBDA? WEBDA Identificationmeta.id;meta.mainintnullableNameNamemeta.idcharSpTypeSpectral Typesrc.spTypecharGmagMagnitude in Gmagphot.mag;em.optfloatPlxParallaxmaspos.parallaxfloate_PlxError in Parallaxmasstat.error;pos.parallaxfloatpmRAProper motion in RAmas/yrpos.pm;pos.eq.rafloate_pmRAError in proper motion in RAmas/yrstat.error;pos.pm;pos.eq.rafloatpmDEProper motion in DEmas/yrpos.pm;pos.eq.decfloate_pmDEError in proper motion in DEmas/yrstat.error;pos.pm;pos.eq.decfloatJ/MNRAS/542/703/table3Stellar parameters for the BSG stars, plus the blue straggler BD+60 345, derived from their FIES spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameNamemeta.idcharSpTypeSpectral Typesrc.spTypecharvsiniProjected rotational velocitykm/sphys.veloc.rotatintvmacMacroturbulent velocitykm/sphys.velocintTeffEffective temperatureKphys.temperature.effectiveintloggGravitylog(cm.s**-2)phys.gravityfloatJ/MNRAS/542/703/tablea1Stars with spectra observed with the INT at R=4000. Parallaxes have been zero-point correctedrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainSpTypeSpectral Typesrc.spTypecharWEBDAWEBDA identificationmeta.id;meta.mainintPlx? Parallaxmaspos.parallaxfloatnullablee_Plx? Error in Parallaxmasstat.error;pos.parallaxfloatnullablepmRA? Proper motion in RAmas/yrpos.pm;pos.eq.rafloatnullablee_pmRA? Error in proper motion in RAmas/yrstat.error;pos.pm;pos.eq.rafloatnullablepmDE? Proper motion in DEmas/yrpos.pm;pos.eq.decfloatnullablee_pmDE? Error in proper motion in DEmas/yrstat.error;pos.pm;pos.eq.decfloatnullableJ/MNRAS/542/703/tablea2Stars with spectra observed with the INT only at R=1400. Parallaxes have been zero-point correctedrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainSpTypeSpectral Typesrc.spTypecharWEBDAWEBDA identificationmeta.id;meta.mainintPlx? Parallaxmaspos.parallaxfloatnullablee_Plx? Error in Parallaxmasstat.error;pos.parallaxfloatnullablepmRA? Proper motion in RAmas/yrpos.pm;pos.eq.rafloatnullablee_pmRA? Error in proper motion in RAmas/yrstat.error;pos.pm;pos.eq.rafloatnullablepmDE? Proper motion in DEmas/yrpos.pm;pos.eq.decfloatnullablee_pmDE? Error in proper motion in DEmas/yrstat.error;pos.pm;pos.eq.decfloatnullableJ/MNRAS/542/703/tablea3Stars with spectra taken with the OHP (R=900) only. Parallaxes have been zero-point correctede_Plx? Error in Parallaxmasstat.error;pos.parallaxfloatnullablepmRA? Proper motion in RAmas/yrpos.pm;pos.eq.rafloatnullablee_pmRA? Error in proper motion in RAmas/yrstat.error;pos.pm;pos.eq.rafloatnullablepmDE? Proper motion in DEmas/yrpos.pm;pos.eq.decfloatnullablee_pmDE? Error in proper motion in DEmas/yrstat.error;pos.pm;pos.eq.decfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainSpTypeSpectral Typesrc.spTypecharWEBDAWEBDA identificationmeta.id;meta.mainintPlx? Parallaxmaspos.parallaxfloatnullableJ/MNRAS/542/703/tablea4Atmospheric parameters for bright non-supergiant cluster members, derived from INT spectraWEBDAWEBDA Identificationmeta.id;meta.mainintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSpTypeSpectral Typesrc.spTypecharvsiniProjected rotational velocitykm/sphys.veloc.rotatintTeffEffective temperatureKphys.temperature.effectiveinte_TeffError in Effective temperatureKstat.error;phys.temperature.effectiveintloggGravitylog(cm.s**-2)phys.gravityfloate_loggError in Gravitylog(cm.s**-2)stat.errorfloatTypeType od stars (Giants, Turn-off, Main-sequence or Mild Be stars)src.classcharJ/MNRAS/542/703/tableb1Coordinates in J2000, ubvy{beta} photometry, and spectral types for Gaia membersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintmoreDisplay the data of tables B1 and B2meta.ref.urlcharRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainVmagMagnitude in Vmagphot.mag;em.opt.Vfloate_VmagError in Vmagstat.error;phot.magfloatNVNumber of measurements in Vmeta.numberint(b-y)Color in b-ymagphot.color;em.opt.B;em.opt.Vfloate_(b-y)Error in b-ymagstat.errorfloatN(b-y)Number of measurements in (b-y)meta.numberintm1Colour index m1magphot.colorfloate_m1Error in m1magstat.errorfloatNm1Number of measurements in m1meta.numberintc1Colour index c1magphot.colorfloate_c1Error in c1magstat.errorfloatNc1Number of measurements in c1meta.numberintbeta? beta indexmagphot.colorfloatnullablee_beta? Error in beta indexmagstat.errorfloatnullableNbeta? Number of measurements in beta indexphot.colorintnullableSpTypeSpectral typesrc.spTypecharJ/MNRAS/542/703/tableb2Coordinates in J2000 and photometric values in E(b-y), Ec1, c0, V0 and MV for Gaia members in NGC 663recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintmoreDisplay the data of tables B1 and B2meta.ref.urlcharRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainE(b-y)Colour excess in (b-y)magphot.color.excessfloatEc1Colour excess in c1magphot.color.excessfloatc0Instrinsic colour in c1magphot.color.reddFreefloatVmag0Intrinsic magnitude in Vmagphot.mag;em.opt.VfloatVMAGAbsolute magnitude in Vmagphys.magAbsfloat