2011A&A...535A..40R


Query : 2011A&A...535A..40R

2011A&A...535A..40R - Astronomy and Astrophysics, volume 535A, 40-40 (2011/11-1)

A spectroscopic investigation of early-type stars in the young open cluster Westerlund 2.

RAUW G., SANA H. and NAZE Y.

Abstract (from CDS):

The distance of the very young open cluster Westerlund2, which contains the very massive binary system WR20a and is likely associated with a TeV source, has been the subject of much debate. We attempt a joint analysis of spectroscopic and photometric data of eclipsing binaries in the cluster to constrain its distance.A sample of 15 stars, including three eclipsing binaries (MSP44, MSP96, and MSP223) was monitored with the FLAMES multi-object spectrograph. The spectroscopic data are analysed together with existing BV photometry.The analysis of the three eclipsing binaries clearly supports the larger values of the distance, around 8kpc, and rules out values of about 2.4-2.8kpc that have been suggested in the literature. Furthermore, our spectroscopic monitoring reveals no clear signature of binarity with periods shorter than 50days in either the WN6ha star WR20b, the early O-type stars MSP18, MSP171, MSP182, MSP183, MSP199, and MSP203, or three previously unknown mid O-type stars. The only newly identified candidate binary system is MSP167. The absence of a binary signature is especially surprising for WR20b and MSP18, which were previously found to be bright X-ray sources. The distance of Westerlund2 is confirmed to be around 8kpc as previously suggested based on the spectrophotometry of its population of O-type stars and the analysis of the light curve of WR20a. Our results suggest that short-period binary systems are not likely to be common, at least not among the population of O-type stars in the cluster.

Abstract Copyright:

Journal keyword(s): binaries: eclipsing - stars: early-type - open clusters and associations: individual: Westerlund2 - sun: fundamental parameters - stars: individual: WR20b - stars: individual: Westerlund 2 MSP18

Nomenclature: Table 1: [RSN2011] A (Nos A-E).

Simbad objects: 34

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Number of rows : 34
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 IC 1805 OpC 02 32 42 +61 27.0   7.03 6.5     ~ 485 2
2 HD 15558 Y*O 02 32 42.5366735903 +61 27 21.582983306 7.82 8.37 7.87 7.34 6.94 O4.5III(f) 302 0
3 RMC 139 WR* 05 38 42.3548071421 -69 04 58.201053806   12.04 11.94     O6.5Iafc+O6Iaf 86 0
4 NGC 2244 OpC 06 31 55 +04 56.5           ~ 577 1
5 V* V578 Mon EB* 06 32 00.6080933581 +04 52 40.879145861 8.01 8.72 8.55 8.09 8.28 B0V+B1V 100 0
6 PSR J1023-5746 Psr 10 23 02.388 -57 46 09.86           ~ 49 0
7 FGES J1023.3-5747 gam 10 23 15.18313 -57 46 34.7840           ~ 53 0
8 Cl* Westerlund 2 MSP 182 * 10 23 56.1788715852 -57 45 30.029039017 15.681 15.965 14.514 13.87 12.411 O4III 14 0
9 V* V712 Car EB* 10 23 58.0120989646 -57 45 48.938103165 15.466 15.473 13.5 12.6   O3If*/WN6+O3If*/WN6 151 1
10 Cl Westerlund 2 OpC 10 23 58.1 -57 45 49   11.59 10.5     ~ 301 0
11 Cl* Westerlund 2 MSP 223 * 10 23 59.192 -57 45 40.27 17.493 17.681 16.015   13.634 O7-8 9 0
12 Cl* Westerlund 2 MSP 44 * 10 24 00.4967154977 -57 44 44.503326361 16.761 16.945 15.587 15.11 13.826 B1V+PMS 13 0
13 Cl* Westerlund 2 MSP 96 * 10 24 00.983 -57 45 05.37 17.275 17.447 16.111 15.85 14.06 B1:+B1: 9 0
14 Cl* Westerlund 2 MSP 167 * 10 24 02.0628053847 -57 45 27.965006608 16.001 16.117 14.453   12.121 O8V 16 0
15 [RSN2011] D * 10 24 02.19 -57 45 31.3 18.023 18.210 16.609   14.389 O9.5: 5 0
16 Cl* Westerlund 2 NRM 4 PM* 10 24 02.302 -57 45 35.14   14.66 13.22 12.47 10.81 O4.5V 10 0
17 Cl* Westerlund 2 MSP 183 * 10 24 02.3604641221 -57 45 30.605449290 15.423 15.496 13.878     O3V(f) 12 0
18 Cl Westerlund 2 5 * 10 24 02.4402256870 -57 44 36.149582896 14.149 14.514 13.155 12.2   O5/5.5V/III(f) 24 0
19 [RSN2011] C * 10 24 02.52 -57 45 31.5 17.250 17.388 15.790   13.474 O7V 5 0
20 [RSN2011] B * 10 24 02.55 -57 45 30.5 17.749 17.892 16.243   13.907 O6-7 4 0
21 [RSN2011] E * 10 24 02.60 -57 45 32.3 17.533 17.697 16.118   13.840 O6-7 5 0
22 Cl* Westerlund 2 MSP 199 * 10 24 02.6481591579 -57 45 34.353113883 15.870 16.082 14.554   12.398 O3V 14 0
23 [RSN2011] A * 10 24 02.7851271273 -57 45 30.011316207 17.418 17.556 15.963   13.714 O8V 6 0
24 Cl* Westerlund 2 MSP 171 * 10 24 04.8971990368 -57 45 28.396379266 15.975 16.134 14.528 13.91 12.307 O5V 14 0
25 GUM 29 HII 10 24 14.6 -57 46 58           ~ 196 0
26 WR 20b WR* 10 24 18.3972653285 -57 48 29.778301585     13.7 12.0   WN6ha 51 0
27 V* DW Car EB* 10 43 10.0816952047 -60 02 11.743736924 9.02 9.83 9.85 10.03 9.59 B1III 68 0
28 Cl Trumpler 16 OpC 10 45 10 -59 43.0   5.35 5.0     ~ 443 0
29 NGC 3603 OpC 11 15 18.6 -61 15 26           ~ 984 1
30 Cl Westerlund 1 OpC 16 47 04.00 -45 51 04.9           ~ 494 0
31 NGC 6231 OpC 16 54 08.51 -41 49 36.0   2.83 2.6     ~ 493 0
32 HD 183143 s*b 19 27 26.5636908636 +18 17 45.191198361 8.25 8.08 6.86 5.74 4.79 B6Ia 416 0
33 Ass Cyg OB 2 As* 20 33.2 +41 19           ~ 831 0
34 Schulte 7 * 20 33 14.1095790591 +41 20 21.903381641 12.24 12.00 10.55     O3If* 133 0

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2021.08.02-08:39:29

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