The historical present is used to make a description of past events more vivid by giving those events a sense of immediacy. Since it's more a matter of style than grammar, it can be hard to come to any definitive conclusions about ambiguous cases. Newspaper headlines typically use it since the news media are in the business of being vivid and immediate, so the events of the day may technically have occurred in the past (even if it's only the past few hours), but it's more gripping to refer to them as if they are happening right now. You may come across better examples in novels or sometimes history, especially where the tense shifts suddenly from past to present in the narration of specific scenes or events, as in some battle narratives. Or when you tell a friend a story but use the present tense to create drama.
How can you tell?
- Did the event definitely occur in the past?
- Does the writer's use of the present tense make the sentence more vivid?
Your examples are all arguably in the historical present, but it's a matter of at least some personal discretion. You could also argue that the events of "today" are still technically part of the present from a newspaper's point of view. I think it's easier to identify the historical present in longer narratives that use it to achieve an obvious dramatic effect, whereas newspaper headlines are at least as much the product of attention-grabbing tactics and the constraints of space as they are of deep, grammatical introspection.
This is just my opinion! The last time I heard anyone discuss the historical present was Latin class.