March 4
Revealing the physics of accretion and outflows from X-ray binaries with XRISM
Dr. Peter Kosec,
CFA/Harvard
Abstract: Compact objects are the most extreme gravitational environments in the Universe, but beyond being simple ‘sinks’ they in fact launch outflows spewing out matter (that can reach near light speeds) and energy, affecting the environments far beyond their gravitational sphere of influence. The best way to study these phenomena in the vicinity of the compact objects is through X-ray spectroscopy. This field is currently undergoing a revolution with the 2023 launch of the XRISM observatory, which carries a microcalorimeter offering 30x better spectral resolution than the current most used X-ray spectrometers. In this talk, I will show how the new high-quality XRISM observations advance our understanding of accretion in X-ray binaries and particularly focus on one X-ray binary, Hercules X-1. Her X-1 is powered by a highly magnetized neutron star and is known for exhibiting a warped, precessing accretion disk that uniquely reveals the accretion flow from different sightlines over time. We recently carried out a large 210 ks observation of Her X-1 during the first XRISM GO cycle. I will discuss how we can use these observations to map the 2D structure of the accretion disk wind of Her X-1 (which is instrumental to constraining its energetics and impact) but also to probe the vicinity of the neutron star in a completely novel way, that may ultimately allow us to study the physics of its interior.
Host: Dr. Cole Miller