Hearing the news,they felt very excited

这里是分词短语做时间状语,句子主干是后面一句.
这句话相当于,
When they heard the news,they felt very excited.
分词短语可以做定语,状语,又根据起做状语的性质不同分为时间状语,地点状语,原因状语,目的状语等等.