Amavasya and monthly tharpanas we perform only for pithrus. But during Chaturmasya period, tharpana is being done on Madhya Ashtami or Maha Barani to the pithrus [forefathers] along with Karunya pithru. We keep additional bhugna for karunya pithrus.
Is there any scriptural reference on what basis we perform tharpana for karunya pithru?
Note on Karunya pithru --- Any elders in the family left home and died in mysterious circumstances, death caused to them by wild animals etc.