2020A&A...636A.109M


Query : 2020A&A...636A.109M

2020A&A...636A.109M - Astronomy and Astrophysics, volume 636A, 109-109 (2020/4-1)

Search for non-thermal X-ray emission in the colliding wind binary Cygnus OB2 #8A.

MOSSOUX E., PITTARD J.M., RAUW G. and NAZE Y.

Abstract (from CDS):


Aims. Cyg OB2 #8A is a massive O-type binary displaying strong non-thermal radio emission. Owing to the compactness of this binary, emission of non-thermal X-ray photons via inverse Compton scattering is expected.
Methods. We first revised the orbital solution for Cyg OB2 #8A using new optical spectra. We then reduced and analysed X-ray spectra obtained with XMM-Newton, Swift, INTEGRAL, and NuSTAR.
Results. The analysis of the XMM-Newton and Swift data allows us to better characterise the X-ray emission from the stellar winds and colliding winds region at energies below 10keV. We confirm the variation of the broad-band light curve of Cyg OB2 #8A along the orbit with, for the first time, the observation of the maximum emission around phase 0.8. The minimum ratio of the X-ray to bolometric flux of Cyg OB2 #8A remains well above the level expected for single O-type stars, indicating that the colliding wind region is not disrupted during the periastron passage. The analysis of the full set of publicly available INTEGRAL observations allows us to refine the upper limit on the non-thermal X-ray flux of the Cyg OB2 region between 20 and 200keV. Two NuSTAR observations (phases 0.028 and 0.085) allow us to study the Cyg OB2 #8A spectrum up to 30keV. These data do not provide evidence of the presence of non-thermal X-rays, but bring more stringent constraints on the flux of a putative non-thermal component. Finally, we computed, thanks to a new dedicated model, the anisotropic inverse Compton emission generated in the wind shock region. The theoretical non-thermal emission appears to be compatible with observational limits and the kinetic luminosity computed from these models is in good agreement with the unabsorbed flux observed below 10keV.

Abstract Copyright: © ESO 2020

Journal keyword(s): stars: early-type - stars: massive - binaries: spectroscopic - stars: individual: Cyg OB2 8A

Simbad objects: 11

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Number of rows : 11
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 * eta Car Em* 10 45 03.5377808928 -59 41 04.051599720 6.37 7.03 6.48 4.90 4.41 OBepec 2342 0
2 HD 166734 s*b 18 12 24.6551425392 -10 43 53.060750040 9.36 9.49 8.42 7.33 6.47 O7.5Iabf 169 0
3 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4138 0
4 HD 193793 WR* 20 20 27.9757908696 +43 51 16.286840244 6.90 7.25 6.85 4.58   WC7p+O5 680 1
5 2MASX J20214907+4400399 Sy2 20 21 49.0191979440 +44 00 39.223779768           ~ 22 0
6 NAME Cyg Complex reg 20 32 +45.0           ~ 565 0
7 [MT91] 213 Be* 20 32 13.1247390384 +41 27 24.346666440 13.12 13.08 11.266     B0Vp 251 0
8 V* V1521 Cyg HXB 20 32 25.78 +40 57 27.9           WN4/5-6/7 1873 2
9 Schulte 9 s*b 20 33 10.7362926720 +41 15 08.222370372 13.38 12.77 10.96     O5I+O4III 216 0
10 Ass Cyg OB 2 As* 20 33.2 +41 19           ~ 882 0
11 BD+40 4227A SB* 20 33 15.0781182864 +41 18 50.479292556 10.42 10.27 8.98 8.03 6.83 O6Ib(fc)+O4.5:III:(fc) 235 0

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2022.10.03-11:20:34

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