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Accretion conditions and morphologies of X-ray transients containing neutronstars are still poorly understood. Circinus X-1 is an enigmatic case where weobserve X-ray flux changes covering four orders of magnitude. We observedCircinus X-1 several times at its very lowest X-ray flux using the high energytransmission grating spectrometer on board the Chandra X-ray Observatory. At aflux of 1.8$\times10^{-11}$ \ergcm we observed a single 1.6 keV blackbodyspectrum. The observed continuum luminosity of 10$^{35}$ \ergsec is about twoorders of magnitude too low to explain the observed photoionized luminositysuggesting a much more complex structure of the X-ray source which is partiallyor entirely obscured as had been previously suggested. This affects mostemissions from the accretion disk including previously observed accretion diskcoronal line emissions. Instead, the strongest observed photoionized lines areblueshifted by about $\sim 400$ \kms\ and we suggest that they originate in theionized wind of a B5Ia supergaint companion supporting a previousidentification. The neutron star in Cir X-1 is very young and should have ahigh magnetic field. At the observed luminosity the emission radius of theblackbody is small enough to be associated with the accretion hot spot as theX-ray emitting region. The small emission radius then points to a fieldstrength below $10^{12}$ G which would be consistent with the observation ofoccasional type I X-ray bursts at high magnetic fields. We discuss Cir X-1 inthe context of being a high-mass X-ray binary with some emphasis on a possibleBe-star X-ray binary nature.

The Origins of X-ray Line Emissions in Circinus~X-1 at Very Low X-ray Flux