The young Be-star binary Circinus X-1

Norbert S. Schulz, Timothy E. Kallman, Sebastian Heinz, Paul Sell, Peter Jonker, William N. Brandt

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Cir X-1 is a young X-ray binary exhibiting X-ray flux changes of four orders of magnitude over several decades. It has been observed many times since the launch of the Chandra X-ray Observatory with high energy transmission grating spectrometer and each time the source gave us a vastly different look. At its very lowest X-ray flux we found a single 1.7 keV blackbody spectrum with an emission radius of 0.5 km. Since the neutron star in Cir X-1 is only few thousand years old we identify this as emission from an accretion column since at this youth the neutron star is assumed to be highly magnetized. At an X-ray flux of 1.8×10-11 erg cm-2 s-1 this implies a moderate magnetic field of a few times of 1011 G. The photoionized X-ray emission line properties at this low flux are consistent with B5-type companion wind. We suggest that Cir X-1 is a very young Be-star binary.

Original languageEnglish (US)
Pages (from-to)125-130
Number of pages6
JournalProceedings of the International Astronomical Union
StateAccepted/In press - Jan 1 2019

All Science Journal Classification (ASJC) codes

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science


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