J/MNRAS/542/703 Stellar evolution in NGC 663 (Marco+, 2025)
NGC 663 as a laboratory for massive star evolution.
Marco A., Negueruela I., Castro N., Simon-diaz S.
<Mon. Not. R. Astron. Soc. 542, 703-734 (2025)>
=2025MNRAS.542..703M 2025MNRAS.542..703M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Photometry, ugriz ; Extinction
Keywords: stars: early-type - stars: emission-line, Be - stars: evolution -
Hertzsprung-Russell and colour-magnitude diagrams - supergiants -
open clusters and associations: individual: NGC 663, NGC 654, NGC 659,
NGC 581, Trumpler 1, CasOB 8
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 104M☉. 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☉,
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☉ 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.
Description:
ALFOSC allows observations in different modes. In imaging mode, the
camera covers a field of 6.5 arcmin x 6.5 arcmin and has a pixel scale
of 0.19 arcsec/pixel. We took Stoemgren photometry from different
frames in order to cover the majority of the stars belonging to the
cluster.
Table 2: Basic parameters for BSG stars in the area of NGC 663 that
were observed with FIES. The spectral types are from this work, the
IDs are taken from the WEBDA data base, and the astrometry corresponds
to Gaia EDR3. Parallaxes have been zero-point corrected. Errors in
derived parameters are dominated by the grid step and can be taken as
±1000K in T eff and ±0.1dex in logg.
Table 3: Stellar parameters for the Blue Supergiant stars, plus the
blue straggler BD + 60 345, derived from their FIES spectra. Errors
are dominated by the grid step
and can be taken as ±1000K in Teff (except for BD +60 369 with
1500K) and ±0.1dex in logg.
Table A1: Stars with spectra observed with INT at R=4000. Parallaxes
have been zero-point corrected.
Table A2: Stars with spectra observed with INT at R=1400. Parallaxes
have been zero-point corrected.
Table A3: Stars with spectra taken with OHP (R=900). Parallaxes have
been zero-point corrected.
Table A4: Atmospheric parameters for bright non-supergiant cluster
members, derived from INT spectra. The values for vsini are simply an
estimate of line broadening, and should not be taken at face value. A
lower limit of 50km/s is given for stars with no evident broadening.
Table B1: Coordinates in J2000, uvbyBeta photometry and spectral types
for Gaia members in NGC 663.
Table B2: Coordinates in J2000 and photometric values in E(b-y), Ec1,
c0, V0, and MV for Gaia members in NGC 663.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 90 10 Basic parameters for BSG stars in the area of
NGC 663 that were observed with FIES
table3.dat 37 11 Stellar parameters for the BSG stars, plus the
blue straggler BD+60 345, derived from
their FIES spectra
tablea1.dat 80 26 Stars with spectra observed with the INT at
R=4000. Parallaxes have been zero-point corrected
tablea2.dat 80 61 Stars with spectra observed with the INT only at
R=1400. Parallaxes have been zero-point corrected
tablea3.dat 80 57 Stars with spectra taken with the OHP (R=900)
only. Parallaxes have been zero-point corrected
tablea4.dat 55 37 Atmospheric parameters for bright non-supergiant
cluster members, derived from INT spectra
tableb1.dat 104 180 Coordinates in J2000, ubvyβ photometry,
and spectral types for Gaia members
tableb2.dat 55 180 Coordinates in J2000 and photometric values in
E(b-y), Ec1, c0, V0 and MV for Gaia members
in NGC 663
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/376/144 : BV(RI)CHα photometry of NGC 663 (Pigulski+, 2001)
J/MNRAS/358/66 : uvbyβ photometry of NGC 663 (Fabregat+, 2005)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 27 I3 --- WEBDA ? WEBDA Identification
29- 38 A10 --- Name Name
40- 48 A9 --- SpType Spectral Type
50- 52 F3.1 mag Gmag Magnitude in G
54- 58 F5.3 mas Plx Parallax
60- 64 F5.3 mas e_Plx Error in Parallax
66- 71 F6.3 mas/yr pmRA Proper motion in RA
73- 77 F5.3 mas/yr e_pmRA Error in proper motion in RA
79- 84 F6.3 mas/yr pmDE Proper motion in DE
86- 90 F5.3 mas/yr e_pmDE Error in proper motion in DE
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Name
13- 21 A9 --- SpType Spectral Type
23- 24 I2 km/s vsini Projected rotational velocity
26- 27 I2 km/s vmac Macroturbulent velocity
29- 33 I5 K Teff Effective temperature
35- 37 F3.1 [cm/s2] logg Gravity
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Byte-by-byte Description of file: tablea1.dat tablea2.dat tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 35 A11 --- SpType Spectral Type
37- 40 I4 --- WEBDA WEBDA identification
42- 46 F5.3 mas Plx ?=- Parallax
48- 52 F5.3 mas e_Plx ?=- Error in Parallax
54- 60 F7.3 mas/yr pmRA ?=- Proper motion in RA
62- 66 F5.3 mas/yr e_pmRA ?=- Error in proper motion in RA
68- 74 F7.3 mas/yr pmDE ?=- Proper motion in DE
76- 80 F5.3 mas/yr e_pmDE ?=- Error in proper motion in DE
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Byte-by-byte Description of file: tablea4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- WEBDA WEBDA Identification
6- 15 A10 --- SpType Spectral Type
20- 22 I3 km/s vsini Projected rotational velocity
24- 28 I5 K Teff Effective temperature
30- 33 I4 K e_Teff Error in Effective temperature
35- 37 F3.1 [cm/s2] logg Gravity
39- 41 F3.1 [cm/s2] e_logg Error in Gravity
43- 55 A13 --- Type Type od stars (Giants, Turn-off,
Main-sequence or Mild Be stars)
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 30 F6.3 mag Vmag Magnitude in V
32- 36 F5.3 mag e_Vmag Error in V
38 I1 --- NV Number of measurements in V
40- 44 F5.3 mag (b-y) Color in b-y
46- 50 F5.3 mag e_(b-y) Error in b-y
52 I1 --- N(b-y) Number of measurements in (b-y)
54- 59 F6.3 mag m1 Colour index m1
61- 65 F5.3 mag e_m1 Error in m1
67 I1 --- Nm1 Number of measurements in m1
69- 73 F5.3 mag c1 Colour index c1
75- 79 F5.3 mag e_c1 Error in c1
81 I1 --- Nc1 Number of measurements in c1
83- 87 F5.3 mag beta ?=- beta index
89- 93 F5.3 mag e_beta ?=- Error in beta index
95 I1 --- Nbeta ?=- Number of measurements in beta index
97-104 A8 --- SpType Spectral type
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Byte-by-byte Description of file: tableb2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 29 F5.3 mag E(b-y) Colour excess in (b-y)
31- 35 F5.3 mag Ec1 Colour excess in c1
37- 42 F6.3 mag c0 Instrinsic colour in c1
44- 49 F6.3 mag Vmag0 Intrinsic magnitude in V
51- 55 F5.2 mag VMAG Absolute magnitude in V
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Acknowledgements:
Amparo Marco, amparo.marco(at)ua.es
(End) Patricia Vannier [CDS] 22-Sep-2025