Gone with the Wind: JWST-MIRI Unveils a Strong Outflow from the Quiescent Stellar-mass Black Hole A0620-00 - UTU Research Portal

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Gone with the Wind: JWST-MIRI Unveils a Strong Outflow from the Quiescent Stellar-mass Black Hole A0620-00

Authors: Zuo, Zihao; Cugno, Gabriele; Michail, Joseph; Gallo, Elena; Russell, David M.; Plotkin, Richard M.; Zou, Fan; Baglio, M. Cristina; Casella, Piergiorgio; Cowie, Fraser J.; Fender, Rob; Gandhi, Poshak; Markoff, Sera; Vincentelli, Federico; Lewis, Fraser; Miller, Jon M.; Miller-Jones, James C. A.; Veledina, Alexandra

Publisher: Institute of Physics Publishing

Publication year: 2025

Journal:: Astrophysical Journal

Article number: 157

Volume: 991

Issue: 2

ISSN: 0004-637X

eISSN: 1538-4357

DOI: https://doi.org/10.3847/1538-4357/adf6b9

Web address : https://doi.org/10.3847/1538-4357/adf6b9

Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/504949516

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.

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Funding information in the publication:
Support for this program (E.G. and Z.Z.) was provided by NASA through grant No. JWST-GO-03832.001-A from the Space Telescope Science Institute. J.M. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-2401752. A.V. acknowledges support from the Academy of Finland grant 355672. D.M.R. is supported by Tamkeen under the NYU Abu Dhabi Research Institute grant CASS. M.C.B. acknowledges support from the INAF-Astrofit fellowship. R.M.P.d s acknowledges support from NASA under award No. 80NSSC23M0104. P.G. thanks The Royal Society (SRF\R1\241074) and UKRI Science & Technology Facilities Council (ST/Y001680/1, ST/V001000/1). Nordita is supported in part by NordForsk. F.M.V. acknowledges support from the European Union’s Horizon Europe research and innovation program through the Marie Skłodowska-Curie grant agreement No. 101149685.