A Shklovsky Mining Graser is a stellar engine typically used to move or destroy a star.
This powerful gamma-ray laser could be aimed to strike a glancing blow at the target star on the side opposite the direction you want it to move. The sun will spew out matter asymmetrically and its orbit is deflecting by a kind of rocket effect.
The energy required to destroy a star by brute force explosive disruption is about 2 x 1041 J. An elegant alternative is an artificial supernova induced in a single star. The graser operating at a wavelength of 1 Angstrom and at power levels of at least 1015 W could focus on a 10-km-wide spot at a star's surface from a safe distance of 10 light-years. It would be have an enormous nuclear reactor that emits most of its laser energy directly as coherent light. This concentrated gamma-ray flux (about 107 watts/m2) should cause exceedingly high temperatures to arise in the outer layers of a star and a spontaneous supernova might result.
About 0.1% of the star's mass would be converted directly into energy, about 1043 joules. A resultant expanding gas cloud may be harvested by interstellar mining engineers, using robots equipped with giant electromagnetic ramscoops.
The Shklovsky Mining Graser can also be used to turn stars off. The beam strikes a glancing blow first on one side, then the other, and so forth. Matter spews equally from either side, so the sun goes nowhere. Sweepships collect and store the unburned stellar hydrogen as it streams from the photosphere.