Neutron Star Bow Shocks
Neutron stars' supersonic motions through the interstellar medium (ISM) generate Balmer-line bow shocks. The shock morphologies are sensitive probes of neutron star winds and the ISM density and neutral fraction.
Ocker & Cosens 2024: We observe three neutron star bow shocks with the Keck Cosmic Web Imager (KCWI) on the 8-m Keck II Telescope. The radial velocity structures of the shocks are resolved for the first time, revealing broad-to-narrow line ratios that are significantly larger than those of non-radiative shocks in supernova remnants. Initial constraints are made on the inclination angles of the neutron star velocities.
Ocker et al. 2021: Monitoring of the Guitar Nebula between 1994 and 2006 with the Hubble Space Telescope reveals temporal evolution of the bow shock. Density variations in the ISM are inferred, and compared to complementary in situ measurements of electron density variations in the very local ISM from Voyager. We find that ISM turbulence is enhanced by several orders of magnitude in the vicinity of the bow shock.