2010A&A...519A.111B


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.01CET14:32:57

2010A&A...519A.111B - Astronomy and Astrophysics, volume 519, A111-111 (2010/9-1)

Non-thermal radio emission from o-type stars. IV. Cygnus OB2 no. 8A.

BLOMME R., DE BECKER M., VOLPI D. and RAUW G.

Abstract (from CDS):

Several early-type colliding-wind binaries are known to emit synchrotron radiation due to relativistic electrons, which are most probably accelerated by the Fermi mechanism. By studying such systems we can learn more about this mechanism, which is also relevant in other astrophysical contexts. Colliding-wind binaries are furthermore important for binary frequency determination in clusters and for understanding clumping and porosity in stellar winds. We study the non-thermal radio emission of the binary Cyg OB2 No. 8A, to see if it is variable and if that variability is locked to the orbital phase. We investigate if the synchrotron emission generated in the colliding-wind region of this binary can explain the observations and we verify that our proposed model is compatible with the X-ray data. We use both new and archive radio data from the Very Large Array (VLA) to construct a light curve as a function of orbital phase. We also present new X-ray data that allow us to improve the X-ray light curve. We develop a numerical model for the colliding-wind region and the synchrotron emission it generates. The model also includes free-free absorption and emission due to the stellar winds of both stars. In this way we construct artificial radio light curves and compare them with the observed one. The observed radio fluxes show phase-locked variability. Our model can explain this variability because the synchrotron emitting region is not completely hidden by the free-free absorption. In order to obtain a better agreement for the phases of minimum and maximum flux we need to use stellar wind parameters for the binary components which are somewhat different from typical values for single stars. We verify that the change in stellar parameters does not influence the interpretation of the X-ray light curve. Our model has trouble explaining the observed radio spectral index. This could indicate the presence of clumping or porosity in the stellar wind, which - through its influence on both the Razin effect and the free-free absorption - can considerably influence the spectral index. Non-thermal radio emitters could therefore open a valuable pathway to investigate the difficult issue of clumping in stellar winds.

Abstract Copyright:

Journal keyword(s): stars: individual: Cyg OB2 No. 8A - stars: early-type - stars: mass-loss - radiation mechanisms: non-thermal - acceleration of particles - radio continuum: stars

Simbad objects: 16

goto Full paper

goto View the reference in ADS

Number of rows : 16

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 HD 168112 ** 18 18 40.8671023267 -12 06 23.366098112 8.81 9.21 8.52 9.24   O5III(f) 138 0
2 QSO B2005+40 QSO 20 07 44.9443187008 +40 29 48.601470737   18.5 19 20.3   ~ 275 1
3 QSO J2015+371 BLL 20 15 28.7298087 +37 10 59.514637     21.82 21.4   ~ 254 2
4 HD 193793 WR* 20 20 27.9763345925 +43 51 16.289775091 6.90 7.25 6.85 4.58   WC7p+O5 657 1
5 ICRF J202206.6+613658 Sy2 20 22 06.68174818 +61 36 58.8047862     19.5 17.58   ~ 304 1
6 4C 31.56 QSO 20 23 19.01734280 +31 53 02.3061150           ~ 103 1
7 ICRF J202355.8+542735 QSO 20 23 55.84400810 +54 27 35.8286624           ~ 33 1
8 QSO B2023+336 BLL 20 25 10.84210 +33 43 00.2144       0   ~ 134 1
9 [MT91] 213 Be* 20 32 13.1248987067 +41 27 24.343749507 13.12 13.08 11.266     B0Vp 225 0
10 BD+40 4220 EB* 20 32 22.4241357648 +41 18 18.942382590 11.32 10.79 9.185     O6.5-7f+O5.5-6f 373 0
11 Schulte 9 s*b 20 33 10.7366753544 +41 15 08.222187463 13.38 12.77 10.96     O4.5If 210 0
12 BD+40 4227A SB* 20 33 15.0780900764 +41 18 50.478859468 10.42 10.27 8.98 8.03 6.83 O6Ib(fc)+O4.5:III:(fc) 220 0
13 Schulte 63 bC* 20 33 18.2825333710 +41 17 39.442034439   17       ~ 11 0
14 3C 418.0 QSO 20 38 37.0346600 +51 19 12.661988   21.30 20.00 18.9   ~ 277 0
15 ICRF J205252.0+363535 Sy2 20 52 52.0549923 +36 35 35.300002   22.083   21.200   ~ 93 1
16 NAME BL Lac BLL 22 02 43.2913773726 +42 16 39.978417860   15.66 14.72     ~ 2037 1

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2010A&A...519A.111B and select 'bookmark this link' or equivalent in the popup menu


2021.03.01-14:32:57

© Université de Strasbourg/CNRS

    • Contact