Using Eclipses to Probe Physical Conditions Along the Jet in the X-Ray Binary SS433

The Galactic X-ray binary SS 433 is the only known astrophysical object to exhibit strong, relativistically red- and blue-shifted emission lines from elements such as S, Si, Fe, Ni. The X-ray emission lines originate in a jet outflow that is launched somewhere very close to the compact accretor (a black hole or a neutron star). Between 2018 August 10-14, SS 433 was observed using the High Energy Transmission Grating Spectrometer system on the Chandra X-ray Observatory, and also using the Neutron star Interior Composition Explorer (NICER) mission aboard the International Space Station. The observations were designed to take advantage of the eclipse and carry out time-resolved spectroscopy and timing studies to infer spatial variation of physical properties such as composition, temperature, and density at different distances along the jet. Preliminary analysis of the Chandra data reveals a plethora of emission lines due to various ionization states of different elements such as Fe XXV, Si XIV, and others. In addition to phenomenological fits to determine properties of the observed emission lines, we will present results from fitting collisionally ionized plasma models, and timing results from NICER.