Thermal cannon

"Weapons with the Heavy (X) Special Rule gain +1 to a Characteristic when Stationary."
When making a Shooting Attack with a Weapon that has the Heavy (X) Special Rule, a modifier of +1 is added to a Characteristic if the Model with that Weapon is part of a Unit that remained Stationary in the Controlling Player’s previous Movement Phase. If the Characteristic listed is AP, then instead it improves the AP by one Step. The value of X in the specific variant of the Heavy (X) Special Rule determines which Characteristic gains the +1 modifier.

"Attacks made with the Blast (X) Special Rule use a Blast Marker to determine how many Hits are caused."
When making attacks with a Weapon that has the Blast (X) Special Rule, before any Hit Tests are made, a Blast Marker must first be placed to determine how many Hits may be inflicted by the attack. The Player making the attack must place the Blast Marker indicated in brackets as part of the Special Rule so that the hole in the middle is entirely over the base of any one model in the Target Unit. Once the blast Marker has been placed, the Player making the attack must make a Hit Test for the attack, and each Model from the Target Unit that is fully or partially under the Blast Marker will suffer 1 Hit if the Hit Test is successful.

*Hits on Other Units*
If any Models form Units other than the Target Unit are fully or partially covered by the Blast Marker, then a new Fire Group must be created for those Hits and set to one side. Continue resolving the Shooting Attack on the original Target Unit, and once that Shooting Attack has been completely resolved begin a new Shooting Attack to resolve those additional Fire Groups generated for Units other than the original Target Unit.

If the Hit Test is unsuccessful then no Hits are inflicted and the Player making the attack must make a Scatter Roll for the Blast Marker (see the Rules for Scatter in the Warhammer: The Horus Heresy - Age of Darkness Rulebook). Once a Scatter Roll has been made for the Blast Marker and it has been moved, one Hit is inflicted on a Unit for each Model from that Unit that is wholly or partially covered by the Blast Marker.

"This Special Rule increases the amount of Damage against Vehicles when Shooting Attacks are made withing a specific range."
If at least one Model in a Unit with the Vehicle Type that is targeted by a Shooting Attack made by a Model using a Weapon with this Special Rule is within a range equal to or less than the value specified by X, that attack has the Armourbane Special Rule and the Damage of Penetrating Hits caused by that attack is doubled.