I Electroweak Feynman Rules: Confusion about the photon-W boson interaction term

[Elmo]

TL;DR

A confusion about the photon-W boson interaction term

This screenshot is from Quantum Field Theory by Mandl and Shaw, 2nd Edition.

I had a question about the vertex factor feynman rule (given below the daigram) of the photon and W+, W- interaction term. Its lagrangian density is given in the third and fourth line of (19.3 a)

What confuses me is the fact that this diagram shows all the momenta directed inwards. Is it the only possible way this coupling can exist or can we also show something like say, the W+ and W- boson momenta directed outwards from the vertex and photon coming inwards ? How will the vertex factor change in that case ? Is it simply a matter of flipping the signs of the momenta in the vertex factor expression ?

Also, is it possible to have a vertex where there is something like a Bremsstrahlung on a single W+ or W- line ?

 

[mfb]

The directions are arbitrary labels. It's like voltages or currents in electric circuits. What direction you use to define them is arbitrary, choosing the opposite direction just flips the sign of all values.

W -> W+photon is possible, sure. Here is a diagram.

 

[Elmo]

Sorry for the late reply.
I just require a bit more clarification on the answer. When @mfb says to flip the signs of all values for oppositely directed momenta, does it mean to flip the signs of momenta only or also of the iota and e ?

Also how will the vertex factor get modified for W->W+photon ?
And how will it be different for W+ and W- ?
I have included a picture of what I think the vertex factors ought to look like, based upon my reference Mandl and Shaw. Do please have a look at it.