Final answer:
A steady X-ray signal with sudden bursts lasting a few seconds each is most likely caused by solar flares, which ionize Earth's atmosphere producing bursts of X-rays. Unlike gamma-ray bursts, which emanate from distant astronomical events, solar flares originate from the sun and can lead to repeated bursts.
Step-by-step explanation:
A steady X-ray signal with sudden bursts lasting a few seconds each is most likely caused by solar flares. Solar flares are known to shower the upper atmosphere of Earth with X-rays, energetic particles, and intense ultraviolet radiation. The bursts of X-rays from solar flares can temporarily increase the ionization in the Earth's atmosphere, leading to the observed sudden bursts in the X-ray signal.
Gamma-ray bursts, on the other hand, are quite different from the steady X-ray signal with sudden bursts. They come from massive stars or the mergers of neutron stars or black holes and can emit gamma rays for a duration ranging from a fraction of a second to a few minutes, and are very distant from Earth. Additionally, gamma-ray bursts occur isotropically, without a preference for any particular area in the sky, and are not associated with a repeated signal from the same location, which contradicts the pattern of a steady X-ray source with bursts.