Final answer:
A star which is hotter than the Sun but smaller is a white dwarf, with Sirius B being an example.
Step-by-step explanation:
To answer the question, a star that is hotter than the Sun but smaller in size is known as a white dwarf. White dwarfs are the remnants of medium-sized stars which have exhausted their nuclear fuel and have collapsed under their own gravity, leading to a highly dense and hot state. An example of such a star is Sirius B, which is smaller in diameters compared to the Sun, yet its surface temperature is much higher, reaching up to 25,200 K.