Either stars are strange, or there are 234 aliens trying to contact us

https://phys.org/news/2016-10-stars-strange-aliens-contact.html

What we’re talking about here is a new study from E.F. Borra and E. Trottier, two astronomers at Laval University in Canada. Their study, titled “Discovery of peculiar periodic spectral modulations in a small fraction of solar type stars” was just published at arXiv.org. ArXiv.org is a pre-print website, so the paper itself hasn’t been peer reviewed yet. But it is generating interest.
The two astronomers used data from the Sloan Digital Sky Survey, and analyzed the spectra of 2.5 million stars. Of all those stars, they found 234 stars that are producing a puzzling signal. That’s only a tiny percentage. And, they say, these signals “have exactly the shape of an ETI signal” that was predicted in a previous study by Borra.

The 2012 paper in the AJ

http://iopscience.iop.org/article/10.1088/0004-6256/144/6/181

Abstract
The main purpose of this article is to make astronomers aware that Searches for Extraterrestrial Intelligence (SETIs) can be carried out by analyzing standard astronomical spectra, including those they have already taken. Simplicity is the outstanding advantage of a search in spectra. The spectra can be analyzed by simple eye inspection or a few lines of code that uses Fourier transform software. Theory, confirmed by published experiments, shows that periodic signals in spectra can be easily generated by sending light pulses separated by constant time intervals. While part of this article, like all articles on SETIs, is highly speculative the basic physics is sound. In particular, technology now available on Earth could be used to send signals having the required energy to be detected at a target located 1000 lt-yr away. Extraterrestrial Intelligence (ETI) could use these signals to make us aware of their existence. For an ETI, the technique would also have the advantage that the signals could be detected both in spectra and searches for intensity pulses like those currently carried out on Earth.

One question remains to be answered. Why would 234 alien civilizations scattered all over the sky all have their com lasers aimed at us?