# NS-Capture Basic Theory

## Simple diagram of capture theory:

This is also a theory of stellar evolution of how a normal giant star (GS) evolves off the main sequence in the H-R diagram and eventually explodes in a supernova explosion (SNE).

```+------------+---------------------+----------------+---------------------------+
|            |                     |                |                           |
|    \       |                     |                |    \ \ \ \ | / / / /      |
|     NS     |      --RS-->        |                |      \ \ \ | / / /        |
|      \     |     ^       \       |     \\||//     |        \ \ | / /          |
|       v    |    (         )      |     --PS->     |     ----       PS--> --   |
|            |    (         )      |    ( \||/ )    |        / / | \ \          |
|   ^        |    (         )      |     <-RS--     |      / / / | \ \ \        |
|    \       |     \       v       |     //||\\     |    / / / / | \ \ \ \      |
|     RS     |      <--NS--        |                |                           |
|      \     |                     |                |                           |
+------------+---------------------+----------------+---------------------------+
|     1      |          2          |        3       |            4              |
+------------+---------------------+----------------+---------------------------+
```

(Note: the diagram above is a placeholder sketch that will eventually be replaced by a more detailed graphic.)

The diagram above shows a simple description of the capture theory, which consists of 4 steps (this example actually describes the process where target regular star is actually a giant star (GS), that expands to form a BeXB in step 2 and then a blue O-star system (HMXB) in step 3):

1. A neutron star (NS) moving through space has a chance near encounter with some kind of regular main sequence star (RS), also moving through space. In this example the regular star (RS) is actually a giant star (GS).
2. As a result of the close encounter in step 1, which resulted in a temporary tidal deformation of the regular star, the NS and RS end up bound together in an elliptical orbit. As a result of ongoing tidal interactions when the NS and RS are at periastron (closest distance during orbit), the NS begins to spin and the RS heats up, and the system develops into a Be X-ray binary (BeXB) (in the case where the RS is a normal giant star (GS)).
(Note the NS and RS are shown switching places from step 1 to step 2 in the diagram in order to emphasize the capture and bound orbit that has emerged, and to show the stars orbiting each other.)
3. As the neutron star spins up after many encounters in the elliptical orbit since the beginning of step 2, the orbit circularizes and the NS is completely enveloped by the atmosphere of the RS. During this phase the NS becomes an X-ray Pulsar (PS), which is generating huge amounts of energy in the form of X-rays that are absorbed by the RS. The RS expands due to the heating from the X-rays to become an O-type supergiant (blue), and the energy it emits is comparable to that of the most powerful X-ray sources (due to the fact that it has an X-ray pulsar spinning around deep in its atmosphere).
4. Finally, when the RS star absorbs enough energy from the PS radiation, the star is so hot, that its gravity is no longer sufficient to hold it together, and it explodes in a supernova (SNE).

The bottom line is that once an NS and an RS have a binding encounter, such as shown in step 1, that then results in a bound elliptical orbit as shown in step 2, then the fate of the RS is sealed. It is on a path to total destruction as shown in steps 3 and 4.

This is a new theory, that shows how normal main sequence giant stars are lifted off the main sequence to become Be X-ray binary stars, and then further lifted above the main sequence to become supergiant O-type stars (high mass x-ray binaries (HMXB’s)), which then ultimately and inevitably result in a supernova explosion that destroys the RS and leaves a rapidly spinning pulsar traveling through the remnants of the RS. In addition the remnants are blown away by the huge radiation from the spinning pulsar.