Kavli Affiliate: Erin Kara
| First 5 Authors: , , , ,
| Summary:
Accretion discs in strong gravity ubiquitously produce winds, seen as
blueshifted absorption lines in the X-ray band of both stellar mass X-ray
binaries (black holes and neutron stars), and supermassive black holes. Some of
the most powerful winds (termed Eddington winds) are expected to arise from
systems where radiation pressure is sufficient to unbind material from the
inner disc ($Lgtrsim L_rm Edd$). These winds should be extremely fast and
carry a large amount of kinetic power, which, when associated with supermassive
black holes, would make them a prime contender for the feedback mechanism
linking the growth of those black holes with their host galaxies. Here we show
the XRISM Resolve spectrum of the Galactic neutron star X-ray binary, GX 13+1,
which reveals one of the densest winds ever seen in absorption lines. This
Compton-thick wind significantly attenuates the flux, making it appear faint,
although it is intrinsically more luminous than usual ($Lgtrsim L_rm Edd$).
However, the wind is extremely slow, more consistent with the predictions of
thermal-radiative winds launched by X-ray irradiation of the outer disc, than
with the expected Eddington wind driven by radiation pressure from the inner
disc. This puts new constraints on the origin of winds from bright accretion
flows in binaries, but also highlights the very different origin required for
the ultrafast ($vsim 0.3c$) winds seen in recent Resolve observations of a
supermassive black hole at similarly high Eddington ratio.
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