Sub-milliarcsecond Optical Interferometry of the HMXB BP Cru with VLTI/GRAVITY

Abstract

We observe the HMXB BP Cru using interferometry in the near-infrared K band with VLTI/GRAVITY. Continuum visibilities are at most partially resolved, consistent with the predicted size of the hypergiant. Differential visibility amplitude ($\Delta |V|\sim 5\%$) and phase ($\Delta \varphi \sim 2°$) signatures are observed across the HeI $2.059\mu$m and Br$\gamma$ lines, the latter seen strongly in emission, unusual for the donor star's spectral type. For a baseline $B\sim 100$m, the differential phase RMS $\sim 0.2°$ corresponds to an astrometric precision of $\sim 2\mu$as. A model-independent analysis in the marginally resolved limit of interferometry reveals asymmetric and extended emission with a strong wavelength dependence. We propose geometric models based on an extended and distorted wind and/or a high density gas stream, which has long been predicted to be present in this system. The observations show that optical interferometry is now able to resolve HMXBs at the spatial scale at which accretion takes place, and therefore probe the effects of the gravitational and radiation fields of the compact object on its environment.

arXiv commentSubmitted to ApJ, 22 pages, 17 figures

References in corpus (25)

• emcee: The MCMC Hammer
• First Light for GRAVITY: Phase Referencing Optical Interferometry for the Very Large Telescope Interferometer
• Catalogue of high-mass X-ray binaries in the Galaxy ($4^{th}$ edition)
• Interferometric data reduction with AMBER/VLTI.Principle,estimators and illustration
• High-Mass X-ray Binaries in the Milky Way: A closer look with INTEGRAL
• A Medium Resolution Near-Infrared Spectral Atlas of O and Early B Stars
• A catalog of bright calibrator stars for 200-meter baseline near-infrared stellar interferometry
• Infrared spectroscopy of low-mass X-ray binaries II
• VLT/UVES spectroscopy of Wray 977, the hypergiant companion to the X-ray pulsar GX301-2
• On the nature of the galactic early-B hypergiants
• The variable cyclotron line in GX 301-2
• On marginally resolved objects in optical interferometry
• First spectro-interferometric survey of Be stars I. Observations and constraints on the disks geometry and kinematics
• Stellar Wind Accretion in GX301-2: Evidence for a High-density Stream
• Orbital phase resolved spectroscopy of GX 301-2 with MAXI
• Inflow and outflow from the accretion disc of the microquasar SS433: UKIRT spectroscopy
• Time, spatial, and spectral resolution of the Halpha line-formation region of Deneb and Rigel with the VEGA/CHARA interferometer
• Stellar wind in state transitions of high-mass X-ray binaries
• Imaging the asymmetric dust shell around CI Cam with long baseline optical interferometry
• Temporal properties of GX 301-2 over a year-long observation with SuperAGILE
• Radio & Optical Interferometry: Basic Observing Techniques and Data Analysis
• Radio emission from the high-mass X-ray binary BP Cru: first detection
• Herschel observations of dust around the high-mass X-ray binary GX 301-2
• The variable stellar wind of Rigel probed at high spatial and spectral resolution
• The close environment of high-mass X-ray binaries at high angular resolution I. VLTI/AMBER and VLTI/PIONIER near-infrared interferometric observations of Vela X-1

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