Context For those interested
A Class 3 Kardashev Civilization has sent a small recon fleet (~1 million ships) to lay siege to system. Sometime after arrival, an extraordinarily dangerous entity is discovered on one of the worlds in the system; posing such a grave threat that it must be immediately destroyed with extreme prejudice. Such is the nature of the threat that your in system ships must be considered a total loss and sending more ships would only add to the losses. So the entire planet, and system for that matter because you can't be too safe, must be destroyed. Naturally, you call in a Super Nova Strike (really a Type 1a) and have the nearest white dwarf jumped into the solar atmosphere (specifically on/in the photosphere, upper convective zone) of the host star.
When I say jumped, I mean the White dwarf does not need to traverse the intervening space. It effectively winks into existence at its destination.
This is the way the civilization handles the situation because reasons, so please no answers containing "they should have done XYZ instead". And the recon fleet lacks the firepower to effectively deal with the threat.
The Meat of the Question
The host star has a mass roughly equal to the sun and the white dwarf is dangerously close to its Chandrasekhar limit, only needing a few hours to accrete the mass needed to push it over the edge and trigger a Super Nova. In the intervening hours before annihilation what happens to the planets in the system now that the host star has effectively doubled its mass? What would those on the surface of the planet experience?