J/A+A/642/A168 Cygnus OB2 O stars spectroscopic analysis (Berlanas+, 2020)
Spectroscopic characterization of the known O-star population in Cygnus OB2.
Evidence of multiple star-forming bursts.
Berlanas S.R., Herrero A., Comeron F., Simon-Diaz S., Lennon D.J.,
Pasquali A., Maiz Apellaniz J., Sota A., Pellerin A.
<Astron. Astrophys. 642, A168 (2020)>
=2020A&A...642A.168B 2020A&A...642A.168B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, O ; Spectroscopy; Associations, stellar ; HR diagrams
Keywords: stars: early-type - stars: massive - stars: fundamental parameters -
Hertzsprung-Russell and C-M diagrams -
open clusters and associations: individual: Cygnus OB2 -
techniques: spectroscopic
Abstract:
Cygnus OB2 provides a unique insight into the high-mass stellar
content in one of the largest groups of young massive stars in our
Galaxy. Although several studies of its massive population have been
carried out over the last decades, an extensive spectroscopic study of
the whole known O-star population in the association is still lacking.
In this work, we created the most complete spectroscopic census of O
stars carried out so far in Cygnus OB2 using already existing and new
spectroscopy. We present the spectra for 78 O-type stars, from which
we identify new binary systems, obtain the distribution of rotational
velocities, and determine the main stellar parameters for all the
stars in the region that have not been detected as double-line
spectroscopic binaries. We also derive radii, luminosities, and masses
for those stars with reliable Gaia astrometry, in addition to creating
the Hertzsprung- Russell Diagram to interpret the evolutionary status
of the association.
This work has shown the improvement reached when using accurate
spectroscopic parameters and astrometry for the interpretation of the
evolutionary status of a population, revealing, in the case of Cygnus
OB2, at least two star-forming bursts at ∼3 and ∼5Myr. We find an
apparent deficit of very fast rotators in the distribution of
rotational velocities. The inspection of the dynamical distribution of
the sample has allowed us to identify nine O stars with peculiar
proper motions and discuss a possible dynamical ejection scenario or
past supernova explosions in the region.
Description:
We built up the most complete spectral sample for the already known
O-type population in Cygnus OB2 by complementing new observations with
already available spectra (own and from collaborators). Our spectral
sample is composed of 78 O-type stars (12 of them previously
classified as SB2). We performed four different campaigns at the Isaac
Newton Telescope (INT) in La Palma. We obtained intermediate-high
resolution, high S/N (100 to 200) spectra for a total of 66 O-type
stars of Cygnus OB2. We used the Intermediate Dispersion Spectrograph
(IDS) and the EEV10 detector, and chose the H1800V grating for the red
wavelength region and the R1200B grating for the blue one. The four
observing runs were held throughout the summer of 2016 and 2017. These
new data have been complemented with already available spectra from
previous observations: our own observations and others drawn from our
collaborators. Most of them comes from GOSSS. We also include spectra
from the Hobby-Eberly Telescope (HET) using the High-Resolution
spectrograph and from the William Herschel Telescope (WHT) using the
ISIS spectrograph.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 99 78 Basic photometric data of the currently known
O-type population of Cygnus OB2
tablea2.dat 115 78 Spectral classification and spectral data used
for our sample of O-stars
tablea3.dat 94 63 Spectroscopic stellar parameters and rotational
velocities of the final O-type sample
tablea4.dat 134 52 Fundamental parameters for the O-type sample
with reliable Gaia astrometry (RUWE<1.4)
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See also:
J/A+A/543/A101 : OB stars in Cygnus OB2 association (Comeron+, 2012)
J/ApJ/643/238 : Chandra/2MASS sources in Cygnus OB2 (Butt+, 2006)
J/ApJS/202/19 : riz photometry in Cyg OB2 (Guarcello+, 2012)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/78] Star identification
5- 14 A10 --- Name ?=- Common object name
20- 36 A17 --- 2MASS 2MASS object name, JHHMMSSss+DDMMSSs
40- 41 I2 h RAh Right Ascension (J2000)
43- 44 I2 min RAm Right Ascension (J2000)
46- 50 F5.2 s RAs Right Ascension (J2000)
54 A1 --- DE- Declination sign (J2000)
55- 56 I2 deg DEd Declination (J2000)
58- 59 I2 arcmin DEm Declination (J2000)
61- 65 F5.2 arcsec DEs Declination (J2000)
69- 73 F5.2 mag Vmag ?=- V magnitude
77 I1 --- r_Vmag ?=- V magnitude reference (1)
82- 86 F5.2 mag Bmag B magnitude (2)
87 A1 --- n_Bmag [*] Note on Bmag (2)
89- 93 F5.2 mag Jmag 2MASS J magnitude
96- 99 F4.2 mag Ksmag ?=- 2MASS Ks magnitude
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Note (1): References as follows:
1 = Values from Massey & Thompson (1991AJ....101.1408M 1991AJ....101.1408M, Cat. J/AJ/101/1408)
2 = Values from Reed (2003AJ....125.2531R 2003AJ....125.2531R, Cat. V/125)
3 = Values from Wright et al. (2015MNRAS.449..741W 2015MNRAS.449..741W, Cat. J/MNRAS/449/741)
4 = Values from Laur et al. (2017A&A...598A.108L 2017A&A...598A.108L, Cat. J/A+A/598/A108)
5 = Values from Tycho-2 catalog (2000A&A...355L..27H 2000A&A...355L..27H, Cat. I/259)
6 = Values from Wesselius et al. (1982A&AS...49..427W 1982A&AS...49..427W, Cat. II/97)
7 = Values from Zacharias et al. (2012yCat.1322....0Z 2012yCat.1322....0Z, Cat. I/322)
Note (2): B magnitudes are from the USNO-B and GOSC catalogs,
from GOSC if * in n_Bmag.
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/78] Star identification
5- 14 A10 --- Name ?=- Common object name
20- 36 A17 --- 2MASS 2MASS object name, JHHMMSSss+DDMMSSs
41- 60 A20 --- SpTypeP Previous spectral type
63- 64 I2 --- r_SpTypeP ?=- Spectral type reference (1)
69- 82 A14 --- SpType ?=- New spectral type (this work)
87- 92 A6 --- Com ?=- Comments (2)
102-103 A2 --- DataA ?=- Sources for broadening measurement (3)
108-115 A8 --- DataB ?=- Sources for spectroscopic analysis (3)
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Note (1): SpT sources from previous works as follows:
1 = Values from Maiz Apellaniz et al. (2019A&A...626A..20M 2019A&A...626A..20M Cat. J/A+A/626/A20)
2 = Values from Berlanas et al. (2018A&A...612A..50B 2018A&A...612A..50B, Cat. J/A+A/612/A50)
3 = Values from Berlanas et al. (2018A&A...620A..56B 2018A&A...620A..56B)
4 = Values from Maiz Apellaniz et al. (2016ApJS..224....4M 2016ApJS..224....4M), Cat. J/ApJS/224/4
5 = Values from Comeron & Pasquali (2012A&A...543A.101C 2012A&A...543A.101C, Cat. J/A+A/543/A101)
6 = Values from Sota et al. (2011ApJS..193...24S 2011ApJS..193...24S, Cat. III/274)
7 = Values from Kiminki et al. (2007ApJ...664.1102K 2007ApJ...664.1102K, Cat. J/ApJ/664/1102)
8 = Values from Hanson (2003ApJ...597..957H 2003ApJ...597..957H)
9 = Values from Negueruela et al. (2008A&A...487..575N 2008A&A...487..575N)
10 = Values from Massey & Thompson (1991AJ....101.1408M 1991AJ....101.1408M, Cat. J/AJ/101/1408)
11 = Values from Morgan et al. (1954PASP...66...85M 1954PASP...66...85M)
12 = Values from Maiz Apellaniz (priv. comment)
13 = Values from Sota et al. (2014ApJS..211...10S 2014ApJS..211...10S, Cat. III/274)
Note (2): Recently classified as O8 III by Roman-Lopes & Roman-Lopes
(2019MNRAS.484.5578R 2019MNRAS.484.5578R).
Note (3): See Table 2 and Sect. 3.2 for further details on sources.
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/78] Object identification
4- 18 A15 --- SpType Spectral type
23- 26 F4.1 kK Teff Effective temperature
31- 33 F3.1 kK e_Teff Effective temperature error
35 A1 --- l_logg Limit flag on logg
36- 40 A5 [cm/s2] logg Surface gravity
43- 46 A4 [cm/s2] e_logg ?=- Surface gravity error
50 A1 --- l_mlogQ Limit flag on mlogQ
51- 55 A5 --- mlogQ Opposit of Wind-strength parameter (-logQ)
59- 61 A3 --- e_mlogQ ?=- Wind-strength parameter error
65 A1 --- l_Yhe Limit flag on Yhe
66- 74 A9 10-2 Yhe Helium abundance
87- 89 I3 10-2 e_Yhe ?=- Helium abundance error
92- 94 I3 km/s vsini Projected rotational velocity (1)
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Note (1): Uncertainties for vsini are in the order of 10-20%
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Byte-by-byte Description of file: tablea4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/78] Object identification
5- 23 I19 --- GaiaDR2 Gaia object source identification
27- 30 I4 pc d Distance (1)
32 A1 --- --- [+]
33- 35 I3 pc E_d Positive error on distance (1)
37 A1 --- --- [-]
38- 40 I3 pc e_d Negative error on distance (1)
44- 47 F4.2 mag Av Visual extinction (2)
50- 54 F5.2 mag VMAG Absolute visual magnitude (2)
56 A1 --- --- [-]
57- 60 F4.2 mag e_VMAG Absolute visual magnitude negative error (2)
63 A1 --- --- [+]
64- 67 F4.2 mag E_VMAG Absolute visual magnitude positive error (2)
71 I1 --- group Membership group (3)
75- 79 F5.2 [Rsun] R Radius
82 A1 --- --- [+]
83- 86 F4.2 [Rsun] E_R Radius positive error
88 A1 --- --- [-]
89- 92 F4.2 [Rsun] e_R Radius negative error
96- 99 F4.2 [Lsun] logL Luminosity
102 A1 --- --- [+]
103-106 F4.2 [Lsun] E_logL Luminosity positive error
109 A1 --- --- [-]
110-113 F4.2 [Lsun] e_logL Luminosity negative error
118-121 F4.1 [Msun] Msp Spectroscopic mass
124 A1 --- --- [+]
125-128 F4.1 [Msun] E_Msp Spectroscopic mass positive error
130 A1 --- --- [-]
131-134 F4.1 [Msun] e_Msp Spectroscopic mass negative error
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Note (1): Distances provided by Bailer-Jones at al. (2018AJ....156...58B 2018AJ....156...58B,
Cat. I/347).
Note (2): Visual extinctions and absolute visual magnitudes have been calculated
using the extinction law derived by Rieke & Lebofsky (1985ApJ...288..618R 1985ApJ...288..618R),
distances derived by Bailer-Jones et al. (2018AJ....156...58B 2018AJ....156...58B, Cat. I/347)
and photometry from Table A.1.
Note (3): Membership groups are from results obtained by Berlanas et al.
(2019MNRAS.484.1838B 2019MNRAS.484.1838B)
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Acknowledgements:
Sara R. Berlanas, sara.rb(at)ua.es
References:
Berlanas et al., 2019MNRAS.484.1838B 2019MNRAS.484.1838B
Berlanas et al., 2018A&A...612A..50B 2018A&A...612A..50B
Wright et al., 2015MNRAS.449..741W 2015MNRAS.449..741W
Comeron & Pasquali, 2012A&A...543A.101C 2012A&A...543A.101C
(End) Sara R. Berlanas [Univ. Alicante], Patricia Vannier [CDS] 26-Aug-2020