I am getting these popups regularly. **They do not appear in the notification center** so I can't find out what app is causing them. The only app I can think of that I have installed recently, I have already deleted and they still appear. I am using the Nexus 4 Android 4.2.2. None of the ad detector apps have found anything. 

How can I determine what is causing this?

Here is a screenshot of an ad, and a screenshot of my task manager immediately after. I am not sure if the app would have to be running to show the ad:

[![The ad](https://i.stack.imgur.com/hLGnDm.jpg)](https://i.stack.imgur.com/hLGnD.jpg) [![The task manager](https://i.stack.imgur.com/yihdFm.jpg)](https://i.stack.imgur.com/yihdF.jpg)