The high-energy emission from HD 93129A near periastron

DEL PALACIO, S; GARCÍA, F; ALTAMIRANO, D; BARBÁ, R H; BOSCH-RAMON, V; CORCORAN, M; DE BECKER, M; HAMAGUCHI, K; MAÍZ APELLÁNIZ, J; MUNAR ADROVER, P; PAREDES, J M; ROMERO, G E; SANA, H; TAVANI, M; UD-DOULA, A

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2020 vol. 494 p. 6043 - 6052

0035-8711

We conducted an observational campaign towards one of the most massive and luminouscolliding wind binaries in the Galaxy, HD 93129A, close to its periastron passage in 2018.During this time the source was predicted to be in its maximum of high-energy emission.Here we present our data analysis from the X-ray satellites Chandra and NuSTAR and theγ-ray satellite AGILE. High-energy emission coincident with HD 93129A was detected inthe X-ray band up to ∼18 keV, whereas in the γ-ray band only upper limits were obtained.We interpret the derived fluxes using a non-thermal radiative model for the wind-collisionregion. We establish a conservative upper limit for the fraction of the wind kinetic powerthat is converted into relativistic electron acceleration, fNT,e < 0.02. In addition, we set alower limit for the magnetic field in the wind-collision region as BWCR > 0.3 G. We alsoargue a putative interpretation of the emission from which we estimate fNT,e ≈ 0.006 andBWCR ≈ 0.5 G. We conclude that multi-wavelength, dedicated observing campaigns duringcarefully selected epochs are a powerful tool for characterising the relativistic particle contentand magnetic field intensity in colliding wind binaries.