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A high-mass X-ray binary descended from an ultra-stripped supernova


Ultra-stripped supernovae are different from other terminal explosions of massive stars, as they show little or no ejecta from the actual supernova event1,2. They are thought to occur in massive binary systems after the exploding star has lost its surface through interactions with its companion2. Such supernovae produce little to no kick, leading to the formation of a neutron star without loss of the binary companion, which itself may also evolve into another neutron star2. Here we show that a recently discovered high-mass X-ray binary, CPD −29 2176 (CD −29 5159; SGR 0755-2933)3,4,5,6, has an evolutionary history that shows the neutron star component formed during an ultra-stripped supernova. The binary has orbital elements that are similar both in period and in eccentricity to 1 of 14 Be X-ray binaries that have known orbital periods and eccentricities7. The identification of the progenitors systems for ultra-stripped supernovae is necessary as their evolution pathways lead to the formation of binary neutron star systems. Binary neutron stars, such as the system that produced the kilonova GW170817 that was observed with both electromagnetic and gravitational energy8, are known to produce a large quantity of heavy elements9,10.

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Fig. 1: Orbital properties of CPD −29 2176.
Fig. 2: The evolution of the binary system.

Data availability

The reduced spectroscopic data that support the plots within this paper and other findings of this study are available from the corresponding author upon request. The raw data are available from the NOIR Lab archive. BPASS results and stellar models are available from

Code availability

The data analysis code used in this analysis is all open-source software. BPASS results and stellar models are available from


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C.P. acknowledges support from the Embry-Riddle Aeronautical University’s Undergraduate Research Institute and the Arizona Space Grant. This research was partially supported through the Embry-Riddle Aeronautical University’s Faculty Innovative Research in Science and Technology (FIRST) Program. The spectroscopy from CTIO was collected through the NOIR Lab program nos. 2018B-0137 and 2020A-0054. This research has used data from the CTIO/SMARTS 1.5m telescope, which is operated as part of the SMARTS Consortium by RECONS ( members T. Henry, H. James, W.-C. Jao and L. Paredes. At the telescope, observations were carried out by R. Aviles and R. Hinojosa.

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Authors and Affiliations



The project was started and the spectroscopy was proposed by H.P., N.D.R. and A.-N.C. J.H. and G.Y. confirmed the astrometry of the neutron star with Swift and Chandra observations, showing it to be coincident with the Be star. C.P. reduced and analysed the spectroscopic data with guidance from N.D.R. The Galactic kinematics were done by P.W. and D.R.G. J.J.E. modelled the binary evolution of the system. All authors discussed and commented on the manuscript.

Corresponding author

Correspondence to Noel D. Richardson.

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The authors declare no competing interests.

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Nature thanks John Antoniadis and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 A typical spectrum of CPD −29 2176 around the He II λ 4686 absorption line.

Gaussian fits to the line were performed with the fitted minimum position representing our derived radial velocity for use in the orbital fits.

Extended Data Fig. 2 The Fourier spectrum of the radial velocities shown in Extended Data Table 1.

The peak at 0.016 d−1 is our derived period for the system, and the noise level in the Fourier spectrum is denoted with a horizontal dashed line at that frequency, showing a 3 σ significance for this peak.

Extended Data Table 1 Measured Radial Velocities of He II 4686 absorption line

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Richardson, N.D., Pavao, C.M., Eldridge, J.J. et al. A high-mass X-ray binary descended from an ultra-stripped supernova. Nature 614, 45–47 (2023).

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