Gone with the Wind: JWST-MIRI Unveils a Strong Outflow from the Quiescent Stellar-mass Black Hole A0620-00
Year: 2025
Type: article
Abstract: We present new observations of the black hole X-ray binary A0620-00 using the Mid-Infrared (MIR) Instrument on the James Webb Space Telescope, during a state where the X-ray luminosity is 9 orders of magnitude below Eddington, and coordinated with radio, near-infrared, and optical observations. The goal is to understand the nature of the excess MIR emission originally detected by Spitzer redward of 8 μm. The stellar-subtracted MIR spectrum is well modeled by a power law with a spectral index of α = 0.72 ± 0.01, where the flux density scales with frequency as F ν ∝ ν α . The spectral characteristics, along with rapid variability—a 40% flux flare at 15 μm and 25% achromatic variability in the 5–12 μm range—rule out a circumbinary disk as the source of the MIR excess. The Low Resolution Spectrometer reveals a prominent emission feature at 7.5 μm, resulting from the blend of three hydrogen recombination lines. While the contribution from partially self-absorbed synchrotron radiation cannot be ruled out, we argue that thermal bremsstrahlung from a warm (a few tens of thousands of Kelvin) wind accounts for the MIR excess; the same outflow is responsible for the emission lines. The inferred mass outflow rate indicates that the system’s low luminosity is due to a substantial fraction of the mass supplied by the donor star being expelled through a wind rather than accreted onto the black hole.
Source: The Astrophysical Journal
Authors: Zihao Zuo, Gabriele Cugno, Joseph Michail, Elena Gallo, David M. Russell, Richard M. Plotkin, Fan Zou, M. Cristina Baglio, Piergiorgio Casella, Fraser J. Cowie, Rob Fender, Poshak Gandhi, Sera Markoff, Federico Vincentelli, Fraser Lewis, Jon M. Miller, James C.A. Miller-Jones, Alexandra Veledina
Institutions: University of Michigan, ZHAW Zurich University of Applied Sciences, University of Zurich, Center for Astrophysics Harvard & Smithsonian, New York University Abu Dhabi, University of Nevada, Las Vegas, University of Nevada, Reno, Brera Astronomical Observatory, National Institute for Astrophysics, Astronomical Observatory of Rome, University of Oxford, University of Cape Town, University of Southampton, University of Amsterdam, Institute for Space Astrophysics and Planetology, Liverpool John Moores University, Cardiff University, Curtin University, International Centre for Radio Astronomy Research, University of Turku, Stockholm University, KTH Royal Institute of Technology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, National Aeronautics and Space Administration, New York University Abu Dhabi, Space Telescope Science Institute, UK Research and Innovation, Royal Society, European Commission, Nuclear Safety and Security Commission, NordForsk, Tamkeen, HORIZON EUROPE Framework Programme
OpenAlex ID: W4414483291