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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
LORD OF THE RINGS: A KINEMATIC DISTANCE TO CIRCINUS X-1 FROM A GIANT X-RAY LIGHT ECHO
Astrophysical Journal, Volume 806, No. 2, Article 265, Year 2015
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Description
Circinus X-1 exhibited a bright X-ray flare in late 2013. Follow-up observations with Chandra and XMM-Newton from 40 to 80 days after the flare reveal a bright X-ray light echo in the form of four well-defined rings with radii from 5 to 13 arcmin, growing in radius with time. The large fluence of the flare and the large column density of interstellar dust toward Circinus X-1 make this the largest and brightest set of rings from an X-ray light echo observed to date. By deconvolving the radial intensity profile of the echo with the MAXI X-ray light curve of the flare we reconstruct the dust distribution toward Circinus X-1 into four distinct dust concentrations. By comparing the peak in scattering intensity with the peak intensity in CO maps of molecular clouds from the Mopra Southern Galactic Plane CO Survey we identify the two innermost rings with clouds at radial velocity ∼ -74 and ∼ -81 km s-1, respectively. We identify a prominent band of foreground photoelectric absorption with a lane of CO gas at ∼ -32 km s-1. From the association of the rings with individual CO clouds we determine the kinematic distance to Circinus X-1 to be DCirX-1 = 9.4-1.0+0.8. This distance rules out earlier claims of a distance around 4 kpc, implies that Circinus X-1 is a frequent super-Eddington source, and places a lower limit of Γ ≳ 22 on the Lorentz factor and an upper limit of θjet ≲ 3° on the jet viewing angle. © 2015. The American Astronomical Society. All rights reserved.
Authors & Co-Authors
Heinz, Sebastian
United States, Madison
University of Wisconsin-madison
Burton, Michael G.
Australia, Sydney
Unsw Sydney
Braiding, Catherine R.
Australia, Sydney
Unsw Sydney
Brandt, William Nielsen
United States, University Park
Pennsylvania State University
Jonker, Peter G.
Netherlands, Utrecht
Sron Netherlands Institute for Space Research
Netherlands, Nijmegen
Radboud Universiteit
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
Sell, Paul H.
United States, Lubbock
Texas Tech University
Fender, Robert P.
United Kingdom, Oxford
University of Oxford
Nowak, Michael A.
United States, Cambridge
Massachusetts Institute of Technology
Schulz, Norbert S.
United States, Cambridge
Massachusetts Institute of Technology
Statistics
Citations: 41
Authors: 9
Affiliations: 9
Identifiers
Doi:
10.1088/0004-637X/806/2/265
ISSN:
0004637X
Study Design
Cross Sectional Study
Cohort Study
Study Approach
Quantitative