This looks great! If it's OK, I would like to make a small suggestion for improvement. It will really help if you can add a reference to a broad stock market indicator (e.g., S&P 500). Without that it is a bit difficult to see whether the impact is due to the event or some other confounding event that affected all the stocks.

I checked the story about Apple's Homepod article in NYT on Feb 6, 2018 and the plot shows that stock prices of Amazon, Google, Microsoft, etc. went up by 4-5% in 24 hours! But when I look at the number from Yahoo Finance, it seems that everything went up and Apple went up more than these companies. The next day all of them went down and then by Feb 9th there was a huge crash. Check out the graph for 5-7 Feb: https://finance.yahoo.com/chart/^GSPC#eyJpbnRlcnZhbCI6ImRheS...