The question of how stellar-mass black holes are born remains open. Theory allows two paths: a quiet collapse without an explosion, or a supernova outburst. For SS 433, the only known Galactic prototype of ultraluminous X-ray sources, there was no direct observational evidence of an explosion. This work joins studies of the W50 nebula and its X-ray lobes, but for the first time draws attention to the region north of the jets, where the signal is not overwhelmed by radiation from the relativistic jets.
The study used archival and new observations from the XMM-Newton space observatory in the soft (0.4–1.2 keV) and hard (2.0–5.0 keV) X-ray bands. To extract the faint diffuse emission, adaptive binning was applied using a weighted Voronoi tessellation algorithm with a signal-to-noise ratio of about 10 per bin. Spectra were extracted separately for the entire shell and for a bright clump in the north; the background was modeled taking into account the local hot bubble, the Galactic halo, and the extragalactic background. Spectral fitting was performed in the XSPEC package using plasma models in nonequilibrium ionization (vnei, vpshock) and in equilibrium (vapec).
North of SS 433, an arc-like structure with a radius of curvature of about 20 arcminutes was found, coinciding with the radio contour and the region of polarized radio emission. The spectrum is described by hot plasma with a temperature of about 1 keV and an ionization timescale of about $10^{10}$ s cm^-3, indicating a shock wave. The silicon abundance exceeds the solar value by a factor of 2–3. Estimates from the Sedov–Taylor model give an age of 17,000–29,000 years and an explosion energy of 0.4–1.4×$10^{51}$ erg, typical for a core-collapse supernova. Alternative scenarios (heating by jets or by an accretion disk wind) were rejected: they yield too low a temperature and luminosity.
The work shows that stellar-mass black holes can be born in ordinary supernova explosions, not only in 'quiet' collapses. This differs from neighboring studies that focused on lobes inflated by jets and did not see the thermal remnant. Here, for the first time, a supernova remnant is identified in the immediate vicinity of an accreting black hole, linking the evolution of the binary system to its explosive past.
The topic could develop toward detailed modeling of the interaction of the supernova remnant with jets and winds, as well as the search for similar shells around other microquasars. Refining the mass of the compact object in SS 433 will allow testing predictions of explosion models.
The results will influence models of black hole formation in binary systems and the interpretation of gamma-ray emission from young supernova remnants.
Deeper X-ray observations are needed to refine plasma parameters and to search for similar shells around other X-ray binaries with black holes.
For high-energy astrophysics, a key unsolved problem is the connection between supernova explosion parameters and the mass of the resulting black hole. This work provides the first observational point on the 'explosion energy–remnant mass' diagram for a real system, which is critical for calibrating theoretical models.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study uses archival and new XMM-Newton observations in the soft and hard X-ray bands. To isolate the faint diffuse emission, we applied adaptive binning based on a weighted Voronoi tessellation algorithm, and the spectra were fitted with non-equilibrium ionization models. To the north of SS 433, we detected an arc-like structure whose spectrum indicates hot plasma with a temperature of about 1 keV and an ionization timescale of 10^10 s cm^-3; Sedov–Taylor model estimates yield an age of 17–29 thousand years and an explosion energy of about 10^51 erg.
Where its strength is
For the first time, a thermal supernova remnant has been identified in the immediate vicinity of an accreting black hole, directly linking the birth of a compact object to a normal massive-star explosion. The method of suppressing jet emission and careful background modeling allowed us to extract the faint shell signal that was previously lost.
Where it could go next
Worth trying
Why this may matter
The discovery of a thermal supernova remnant near SS 433 provides direct observational confirmation of the connection between a massive star explosion and the birth of a black hole in a binary system. This could become a key piece in understanding the formation of ultraluminous X-ray sources and the evolution of close binaries with compact objects.
Nearby works in our archive
The archive is sparse around this work: the closest review is only 0.57, against a usual 0.64. It looks like few have drilled nearby.
The W50 nebula, which hosts SS 433, resembles a manatee in shape, earning it the nickname 'Manatee Nebula'.