J/MNRAS/449/741 The massive star population of Cygnus OB2 (Wright+, 2015)
The massive star population of Cygnus OB2.
Wright N.J., Drew J.E., Mohr-Smith M.
<Mon. Not. R. Astron. Soc. 449, 741 (2015)>
=2015MNRAS.449..741W 2015MNRAS.449..741W
ADC_Keywords: Associations, stellar ; Stars, OB ; Stars, ages ; Stars, masses
Keywords: stars: early-type - stars: massive -
open clusters and associations: individual: Cygnus OB2
Abstract:
We have compiled a significantly updated and comprehensive census of
massive stars in the nearby Cygnus OB2 association by gathering and
homogenising data from across the literature. The census contains 169
primary OB stars, including 52 O-type stars and 3 Wolf-Rayet stars.
Spectral types and photometry are used to place the stars in a
Hertzprung-Russell diagram, which is compared to both non-rotating and
rotating stellar evolution models, from which stellar masses and ages
are calculated. The star formation history and mass function of the
association are assessed, and both are found to be heavily influenced
by the evolution of the most massive stars to their end states. We
find that the mass function of the most massive stars is consistent
with a "universal" power-law slope of Γ=1.3. The age
distribution inferred from stellar evolutionary models with rotation
and the mass function suggest the majority of star formation occurred
more or less continuously between 1 and 7Myr ago, in agreement with
studies of low- and intermediate mass stars in the association. We
identify a nearby young pulsar and runaway O-type star that may have
originated in Cyg OB2 and suggest that the association has already
seen its first supernova. Finally we use the census and mass function
to calculate the total mass of the association of
16500+3800-2800M_☉, at the low end, but consistent with,
previous estimates of the total mass of Cyg OB2. Despite this Cyg OB2
is still one of the most massive groups of young stars known in our
Galaxy making it a prime target for studies of star formation on the
largest scales.
Description:
We present observational (AV), derived (Teff and Lbol) and
stellar parameters (Mass, Age) for OB stars in the Cygnus OB2
association derived from literature photometry and spectroscopy, which
is also included. The stellar parameters are derived using both
non-rotating and rotating stellar evolutionary models. Uncertainties
are presented for all quantities, calculated using a Monte Carlo
simulation.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
census.dat 231 167 Stellar photometry, spectral types and derived
quantities, with uncertainties
refs.dat 63 19 References
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See also:
J/AJ/107/1433 : Cygnus OB2 polarimetry (Kobulnicky+, 1994)
J/A+AS/111/407 : VI Cygni red + reddened stars (Parthasarathy+, 1995)
J/MNRAS/298/753 : Variables in Cygnus OB2 (Pigulski+ 1998)
J/ApJS/149/123 : WSRT survey of Cygnus OB2 (Setia Gunawan+, 2003)
J/ApJ/643/238 : Chandra/2MASS sources in Cygnus OB2 (Butt+, 2006)
J/A+A/464/211 : Chandra and near-IR obs. of Cyg OB2 (Albacete Colombo+, 2007)
J/A+A/472/557 : Cygnus OB2 region 610MHz sources (Marti+, 2007)
J/A+A/474/495 : Cygnus OB2 young stars X-ray flares (Albacete Colombo+, 2007)
J/A+A/486/453 : NIR photometry of early-type stars in Cyg OB2 (Comeron+ 2008)
J/ApJS/184/84 : X-ray sources in Cyg OB2 region (Wright+, 2009)
J/ApJS/194/27 : Variable stars in Cygnus OB2 (Henderson+, 2011)
J/ApJS/202/19 : riz photometry in Cyg OB2 (Guarcello+, 2012)
J/A+A/543/A101 : OB stars in Cygnus OB2 association (Comeron+, 2012)
J/ApJ/713/871 : Massive star-forming region Cygnus OB2. II. (Wright+, 2012)
J/ApJ/751/4 : Radial velocities of massive stars in Cyg OB2 (Kiminki+ 2012)
J/ApJ/773/135 : Disk-bearing stars in Cygnus OB2 (Guarcello+, 2013)
J/ApJS/213/34 : Velocities of Cygnus OB2 massive binaries (Kobulnicky+, 2014)
Byte-by-byte Description of file: census.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000.0)
4- 5 I2 min RAm Right ascension (J2000.0)
7- 11 F5.2 s RAs Right ascension (J2000.0)
12 A1 --- DE- Declination sign (J2000)
13- 14 I2 deg DEd Declination (J2000.0)
16- 17 I2 arcmin DEm Declination (J2000.0)
19- 22 F4.1 arcsec DEs Declination (J2000.0)
24- 39 A16 --- SpType Spectral type of star and binary companions
41- 51 A11 --- r_SpType References for spectral types (comma
separated, one reference for each star in
the system), in refs.dat file
53- 54 A2 --- Schulte Star number in the Schulte system (1)
56- 58 I3 --- [MT91] ?=- Star number from Massey and Thompson (2)
60- 64 A5 --- ONames Other star names and numbers (3)
66- 70 F5.2 mag AV [2.1/10.2]?=- Extinction in the V band
72- 75 F4.2 mag E_AV ?=- Upper 1-σ uncertainty on AV
77- 80 F4.2 mag e_AV ?=- Lower 1-σ uncertainty on AV
82- 85 F4.2 [Lsun] logL [2.4/6.2]?=- Logarithm (base 10) of the
bolometric luminosity
87- 90 F4.2 [Lsun] E_logL ?=- Upper 1-σ uncertainty on logL
92- 95 F4.2 [Lsun] e_logL ?=- Lower 1-σ uncertainty on logL
97-100 F4.2 [K] logT [4.1/5.1]?=- Logarithm (base 10) of the
effective temperature
102-105 F4.2 [K] E_logT ?=- Upper 1-σ uncertainty on logT
107-110 F4.2 [K] e_logT ?=- Lower 1-σ uncertainty on logT
112 A1 --- l_M1 Limit flag on M1
113-117 F5.1 Msun M1 [4.3/110]?=- Stellar mass derived from
rotating stellar evolutionary models
(recommended) (4)
119-123 F5.2 Msun E_M1 ?=- Upper 1-σ uncertainty on M1
125-129 F5.2 Msun e_M1 ?=- Lower 1-σ uncertainty on M1
131-135 F5.2 Myr Age1 [0/10]?=- Age derived from rotating stellar
models (recommended) (4) (5)
136 A1 --- --- [-] When Age1 interval
137 I1 Myr Age1M ? Upper value of Age1 interval
139-143 F5.2 Myr E_Age1 ?=- Upper 1-σ uncertainty on Age1
145-148 F4.2 Myr e_Age1 ?=- Lower 1-σ uncertainty on Age1
150 A1 --- l_M0 Limit flag on M0
151-155 F5.1 Msun M0 [4.4/112]?=- Stellar mass derived from
non-rotating stellar evolutionary models (6)
157-161 F5.2 Msun E_M0 ?=- Upper 1-σ uncertainty on M0
163-167 F5.2 Msun e_M0 ?=- Lower 1-σ uncertainty on M0
169-173 F5.2 Myr Age0 [0/10]?=- Age derived from non-rotating
stellar models (5) (6)
174 A1 --- --- [-] When Age0 interval
175 I1 Myr Age0M ? Upper value of Age_n interval
177-181 F5.2 Myr E_Age0 ?=- Upper 1-σ uncertainty on Age0
183-186 F4.2 Myr e_Age0 ?=- Upper 1-σ uncertainty on Age0
188-192 F5.2 mag Umag ?=- U band magnitude
194-198 F5.2 mag Bmag ?=- B band magnitude
200-204 F5.2 mag Vmag ?=- V band magnitude
206 A1 --- r_Vmag [MU-] Flag indicating origin of the UBV
photometry (7)
208-213 F6.3 mag Jmag ?=- J band magnitude
215-220 F6.3 mag Hmag ?=- H band magnitude
222-227 F6.3 mag Kmag ?=- K band magnitude
230-231 A2 --- r_Kmag [2M U] Flag indicating origin of the JHK
photometry (8)
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Note (1): Schulte numbering from Johnson & Morgan (1954ApJ...119..344J 1954ApJ...119..344J).
Note (2): From Massey & Thompson (1991AJ....101.1408M 1991AJ....101.1408M, Cat. J/AJ/101/1408).
Note (3): Primarily star numbers from Comeron et al. (2002A&A...389..874C 2002A&A...389..874C,
ANN, [CPR2002] ANN in Simbad), Comeron et al. (2008A&A...486..453C 2008A&A...486..453C,
Cat. J/A+A/486/453, [CPF2008] NNN in Simbad) and Comeron & Pasquali
(2012A&A...543A.101C 2012A&A...543A.101C, Cat. J/A+A/543/A101), as well as known Wolf-Rayet
stars (labelled with WR).
Note (4): Ekstrom et al. (2012A&A...537A.146E 2012A&A...537A.146E, Cat. J/A+A/537/A146).
Note (5): Stars whose positions on the HR diagram suggest ages >10Myr have
unconstrained ages and are listed as having an age of "10" with uncertainties
of "0". Stars to the left of the zero-aged main sequence are listed as
having ages of "0" with lower 1-σ uncertainties listed as "0".
Note (6): Lejeune & Schaerer (2001A&A...366..538L 2001A&A...366..538L).
Note (7): UBVflag as follows:
M = photometry taken from Massey & Thompson 1991 (J/AJ/101/1408)
U = photometry converted from UVEX photometry from Groot et al. 2009
(J/MNRAS/399/323)
- = no photometry was available in any of these bands
Note (8): JHK flag as follows:
2M = photometry taken from the 2MASS catalog, Cutri et al. 2003 (II/246)
U = photometry converted from UKIDSS photometry from Lucas et al.
(2008MNRAS.391..136L 2008MNRAS.391..136L)
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Ref Reference code
6- 24 A19 --- BibCode Bibcode
26- 43 A18 --- Aut Author's name
45- 63 A19 --- Rem Remarks
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Acknowledgements:
Nicholas J. Wright, nick.nwright(at)gmail.com
(End) Nicholas Wright [Hertfordshire, UK], Patricia Vannier [CDS] 13-Jan-2015