https://en.wikipedia.org/wiki/Gamma-ray_burst :

> (GRBs) are extremely energetic events occurring in distant galaxies that represent the brightest and most powerful class of explosion in the Universe.

> The sources of most GRB are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime)[11] and extremely rare (a few per galaxy per million years).

> All in all, a GRB within a few kiloparsecs, with its energy directed towards Earth, will mostly damage life by raising the UV levels during the burst itself and for a few years thereafter.

I'm guessing without an atmosphere protecting a ship it'd be a bit worse? But it's like winning a very bad lottery to get hit by one. I guess if you're traveling thousands of years in deep sleep odds get higher?