2013A&A...550A..27M


Query : 2013A&A...550A..27M

2013A&A...550A..27M - Astronomy and Astrophysics, volume 550A, 27-27 (2013/2-1)

A spectroscopic investigation of the o-type star population in four Cygnus OB associations. I. Determination of the binary fraction.

MAHY L., RAUW G., DE BECKER M., EENENS P. and FLORES C.A.

Abstract (from CDS):

Establishing the multiplicity of O-type stars is the first step towards accurately determining their stellar parameters. Moreover, the distribution of the orbital parameters provides observational clues to the way that O-type stars form and to the interactions during their evolution. Our objective is to constrain the multiplicity of a sample of O-type stars belonging to poorly investigated OB associations in the Cygnus complex and for the first time to provide orbital parameters for binaries identified in our sample. Such information is relevant to addressing the issue of the binarity in the context of O-type star formation scenarios. We performed a long-term spectroscopic survey of nineteen O-type stars. We searched for radial velocity variations to unveil binaries on timescales from a few days up to a few years, on the basis of a large set of optical spectra. We confirm the binarity for four objects: HD193443, HD228989, HD229234, and HD194649. We derive for the first time the orbital solutions of three systems, and we confirm the values of the fourth, showing that these four systems all have orbital periods shorter than 10 days. Besides these results, we also detect several objects that show non-periodic line profile variations in some of their spectral lines. These variations mainly occur in the spectral lines that are generally affected by the stellar wind and are not likely to be related to binarity. The minimal binary fraction in our sample is estimated to be 21%, but it varies from one OB association to the next. Indeed, 3 O stars of our sample out of 9 (33%) belonging to CygOB1 are binary systems, 0% (0 out of 4) in CygOB3, 0% (0 out of 3) in CygOB8, and 33% (1 out of 3) in CygOB9. Our spectroscopic investigation also stresses the absence of long-period systems among the stars in our sample. This result contrasts with the case of the O-type stellar population in NGC2244 among which no object showed radial velocity variations on short timescales. However, we show that it is probably an effect of the sample and that this difference does not a priori suggest a somewhat different star forming process in these two environments.

Abstract Copyright:

Journal keyword(s): stars: early-type - binaries: spectroscopic - open clusters and associations: individual: Cygnus OB1 - clusters open, individual: Cygnus OB3 - open clusters and associations: individual: Cygnus OB8 - open clusters and associations: individual: Cygnus OB9

VizieR on-line data: <Available at CDS (J/A+A/550/A27): stars.dat table2.dat>

Simbad objects: 39

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Number of rows : 39
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 IC 1805 OpC 02 32 50 +61 28.3   7.03 6.5     ~ 497 2
2 NAME Rosette OB Association As* 06 31.7 +04 58           ~ 140 0
3 HD 46149 SB* 06 31 52.5319291296 +05 01 59.178678024 7.03 7.80 7.61 7.54 7.36 O8.5V 265 0
4 HD 46150 Em* 06 31 55.5205071744 +04 56 34.296516096 6.03 6.86 6.73 6.50 6.41 O5V((f))z 382 0
5 NGC 2244 OpC 06 32 11 +04 54.8           ~ 590 1
6 HD 46573 SB* 06 34 23.5692982800 +02 32 02.944339980 7.61 8.27 7.93     O7V((f))z 123 0
7 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4122 0
8 HD 227018 * 19 59 49.1028248712 +35 18 33.550210836 8.75 9.35 9.00     O6.5V((f))z 97 0
9 HD 227245 * 20 02 21.7187728800 +35 40 29.825201568 9.92 10.25 9.69     O7V((f))z 45 0
10 HD 227586 * 20 05 36.3637223736 +35 37 23.492927568 8.39 8.98 8.86     B0.5IVp 51 0
11 HD 190864 Em* 20 05 39.8022808800 +35 36 27.991297908 7.18 7.93 7.78     O6.5III(f) 218 0
12 HD 190918 WR* 20 05 57.3244526328 +35 47 18.150756792 6.11 6.88 6.75     WN5+O9I 358 0
13 NGC 6871 OpC 20 06 12 +35 45.9   5.43 5.2     ~ 207 0
14 Ass Cyg OB 3 As* 20 07 +35.9           ~ 177 0
15 HD 227757 * 20 07 12.7698932544 +36 21 33.434934012 8.63 9.41 9.27     O9.5V 57 0
16 HD 191201 ** 20 07 23.6846928338 +35 43 05.890234225 6.66 7.43 7.34     O9III+O9V 113 0
17 HD 191423 * 20 08 07.1135347944 +42 36 21.962454480 7.43 8.19 8.03     ON9II-IIInn 105 0
18 HD 191978 * 20 10 58.2799378920 +41 21 09.926824572 7.38 8.15 8.03     O8Vz 65 0
19 Ass Cyg OB 8 As* 20 15 +40.9           ~ 69 0
20 HD 193117 * 20 16 59.8875650112 +40 50 37.381198056 8.89 9.26 8.79     O9.5II 32 0
21 Ass Cyg OB 1 As* 20 17.8 +37 38           ~ 259 1
22 HD 228841 Em* 20 18 29.6946566952 +38 52 39.774824724 9.08 9.50 9.01     O6.5Vn((f)) 56 0
23 HD 193443 SB* 20 18 51.7093796362 +38 16 46.504188062 7.11 7.59 7.26     O8.5III:((f))+O9.2:IV: 139 0
24 HD 193514 Em* 20 19 08.4971150880 +39 16 24.253036608 7.32 7.83 7.38     O7Ib(f) 182 0
25 HD 193595 * 20 19 31.3267230384 +39 03 26.230564836 8.5 9.08 8.78     O7V((f)) 57 0
26 HD 193682 Em* 20 20 08.9387110032 +37 49 51.313158876 8.44 8.87 8.42     O4.5IV(f) 83 0
27 Cl Berkeley 86 OpC 20 20 20 +38 41.3           ~ 113 0
28 HD 228989 SB* 20 20 21.3976505040 +38 41 59.688769308 10.29 10.49 9.686     O9.5V+O9.5V 33 0
29 Ass Cyg OB 9 As* 20 21 +39.9           ~ 126 0
30 HD 194094 * 20 22 20.9580075912 +38 43 29.470174176 9.22 9.57 9.05     O8.5III 39 0
31 HD 194280 s*b 20 23 26.3118358272 +38 56 21.030835740 8.94 9.08 8.42     OC9.7Iab 73 0
32 HD 194334 Em* 20 23 35.4603904008 +38 52 56.583463044 9.45 9.52 8.83     O7.5V 30 0
33 M 29 OpC 20 23 46 +38 29.2   7.30 6.6     ~ 231 0
34 HD 229234 SB* 20 24 01.2995078760 +38 30 49.566276036 9.5 9.58 8.94     O9III 72 0
35 HD 194649 SB* 20 25 22.1272777920 +40 13 01.206964704 9.86 9.93 9.07     O5.5V((f))+O7Vz 44 0
36 HD 195213 * 20 28 32.0275383864 +40 49 02.898008652 9.32 9.55 8.82     O7 40 0
37 NAME Cyg Complex reg 20 32 +45.0           ~ 561 0
38 Ass Cyg OB 2 As* 20 33.2 +41 19           ~ 878 0
39 Ass Cyg OB 7 As* 21 08 +47.6           ~ 205 0

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2022.08.10-18:45:54

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