Einstein delay

The Einstein delay is a delay caused due to relativity when electromagnetic radiation (specifically, an EMR event whose reception can be timed, such as a pulse or other transient) passes from an object with a particular velocity and acceleration and/or within a gravitational well. It is the time-dilation effects of general relativity (GR) that occur under such a circumstance. Reception timing is similarly affected by its receiver's velocity, acceleration, and location within a gravitational field, but I'm not certain whether the receiver's circumstances all lengthen the delay rather than shorten it. Special relativity produces time dilation due to velocity, and GR additionally produces effects from acceleration and gravity. For example, the timing of pulses received from a pulsar is affected both by the pulsar's velocity, acceleration, and gravitational field, and by the analogous effects on Earth within the solar system.

In addition to the Einstein delay are the Roemer delay (and any analogous delay due to the pulsar's orbit), and the Shapiro delay, which is also a GR effect, but is an added delay due to the EMR route passing close to a massive object. The Einstein delay includes the effects of Earth's position within the solar system's gravitational well, i.e., how deep Earth is within the well, but additionally, if the sight line between Earth and the pulsar passes close to the Sun, a received pulse is delayed additionally compared to what it would be given a sight line substantially away from the Sun, i.e., a Shapiro Delay. A line of sight passing close to a planet (e.g., Jupiter) could also create a significant Shapiro delay.

These delays (Einstein, Shapiro, and Roemer) are relevant to the processing of pulsar-timing-array (PTA) data, and also to tests of GR using pulsars, such as measuring the Hulse-Taylor Binary's orbital decay.