Space Sciences/Astrophysics Seminar with Joseph Neilsen on Revealing the Most Extreme Accretion Disk Winds with XRISM

Accretion disk winds from compact objects are ubiquitous across the mass scale. Seen in high-resolution X-ray spectra as blueshifted absorption lines, these highly-ionized outflows carry away the vast majority of infalling matter, regulating accretion rates and shaping the evolution and appearance of their compact objects. Some of the most powerful winds are expected at the Eddington limit, where radiation pressure can drive relativistic outflows from the inner disk. In this context, I will present the first spectrum of the neutron star X-ray binary GX 13+1 from the XRISM Resolve spectrometer, which reveals in exquisite detail one of the highest column density winds ever seen in X-ray absorption lines. This Compton-thick wind significantly attenuates the X-ray flux, such that the source appears fainter than usual but must in fact be radiating at or above the Eddington limit. The wind is much slower than expected for such a high-luminosity source, but is similar to other strong winds from X-ray binaries. Coupled with evidence for a recurrent super-Eddington phase in GX 13+1, I will argue that this XRISM spectrum suggests that transient Compton thick obscuration must be more common in X-ray binaries than we once thought.

Joseph Neilsen is an assistant professor in the Physics Department at Villanova University and an expert in high-resolution X-ray spectroscopy and spectral variability of black holes. His research focuses on black holes and neutron stars in the Milky Way galaxy. As an observational astrophysicist, he uses space- and ground-based telescopes (Chandra, NuSTAR, XRISM, JVLA, Gemini) to study the behavior of these extreme gravitational objects.

Sponsored by the McDonnell Center for the Space Sciences.