We use cookies to ensure that we give you the best experience on our website. You can change your cookie settings at any time. Otherwise, we'll assume you're OK to continue.

Durham University

Department of Physics

Staff profile

Publication details for Prof Tim Roberts

Siwek, M., Sadowski, A., Narayan, R., Roberts, T.P. & Soria, R. (2017). Optical and X-ray luminosity of expanding nebulae around ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society 470(1): 361-371.

Author(s) from Durham


We have performed a set of simulations of expanding, spherically symmetric nebulae inflated by winds from
accreting black holes in ultraluminous X-ray sources (ULXs). We implemented a realistic cooling function
to account for free-free and bound-free cooling. For all model parameters we considered, the forward shock
in the interstellar medium becomes radiative at a radius ∼ 100 pc. The emission is primarily in the optical
and UV, and the radiative luminosity is about 50% of the total kinetic luminosity of the wind. In contrast,
the reverse shock in the wind is adiabatic so long as the terminal outflow velocity of the wind vw & 0.003c.
The shocked wind in these models radiates in X-rays, but with a luminosity of only ∼ 1035 erg s−1
. For wind
velocities vw . 0.001c, the shocked wind becomes radiative, but it is no longer hot enough to produce Xrays.
Instead it emits in optical and UV, and the radiative luminosity is comparable to 100% of the wind
kinetic luminosity. We suggest that measuring the optical luminosities and putting limits on the X-ray and
radio emission from shock-ionized ULX bubbles may help in estimating the mass outflow rate of the central
accretion disk and the velocity of the outflow.