VIDEO: PSR J2215+5135
Orbital period: 4.14 hours
Spin period: 2.61 milliseconds
Distance from Earth: about 10.000 light-years
The inner face of the companion star, strongly irradiated by the pulsar, is heated up to about 8100 degrees Kelvin. As a consequence, hydrogen absorption lines dominate the visible spectrum of the hot side of the star.
The outer face of the companion star is shielded from the pulsar wind, and remains at about 5700 degrees Kelvin. As a consequence, magnesium absorption lines are stronger on its cold side.
This allowed astronomers to measure the velocity of both sides of the companion, finding one of the most massive neutron stars known to date: about 2.3 times heavier than the Sun!
Design: G. Pérez-Diaz, IAC
Binary simulations: R. Hynes, LSU
For more info: M. Linares, T. Shahbaz, J. Casares (2018, ApJ)