Radio emission from the high-mass X-ray binary BP Cru: first detection

Abstract

BP Cru is a well known high-mass X-ray binary composed of a late B hypergiant (Wray 977) and a neutron star, also observed as the X-ray pulsar GX 301-2. No information about emission from BP Cru in other bands than X-rays and optical has been reported to date in the literature, though massive X-ray binaries containing black holes can have radio emission from a jet. In order to assess the presence of a radio jet, we searched for radio emission towards BP Cru using the Australia Compact Array Telescope during a survey for radio emission from Be/X-ray transients. We probed the 41.5d orbit of BP Cru with the Australia Telescope Compact Array not only close to periastron but also close to apastron. BP Cru was clearly detected in our data on 4, possibly 6, of 12 occasions at 4.8 and 8.6 GHz. Our data suggest that the spectral index of the radio emission is modulated either by the X-ray flux or the orbital phase of the system. We propose that the radio emission of BP Cru probably arises from two components: a persistent component, coming from the mass donor Wray 977, and a periodic component connected to the accretion onto the neutron star, possibly coming from a (weak and short lived) jet.

2 figures, accepted for publication in A+A letters

References in corpus (3)

• The 2003 Outburst of the X-ray Transient H 1743-322: Comparisons with the Black Hole Microquasar XTE J1550-564
• VLT/UVES spectroscopy of Wray 977, the hypergiant companion to the X-ray pulsar GX301-2
• Stellar Wind Accretion in GX301-2: Evidence for a High-density Stream

Cited by in corpus (10)

• A new radio census of neutron star X-ray binaries
• Revisiting the archetypical wind accretor Vela X-1 in depth -- A case study of a well-known X-ray binary and the limits of our knowledge
• Identification of a Population of X-ray Emitting Massive Stars in the Galactic Plane
• Sub-milliarcsecond Optical Interferometry of the HMXB BP Cru with VLTI/GRAVITY
• Radio emission from the X-ray pulsar Her X-1: a jet launched by a strong magnetic field neutron star?
• Temporal properties of GX 301-2 over a year-long observation with SuperAGILE
• Radio monitoring of transient Be/X-ray binaries and the inflow-outflow coupling of strongly-magnetized accreting neutron stars
• Discovery of radio emission from the symbiotic X-ray binary system GX 1+4
• Herschel observations of dust around the high-mass X-ray binary GX 301-2
• Low-frequency spectra of neutron star + OB supergiant binaries: Does wind density drive persistent and flaring modes of accretion?