Megan, Cueball, and Ponytail are observing the results from a gravitational wave detector (see details below). This comic came out on the day that the first direct observation of gravitational waves was publicly announced on 2016-02-11. The actual event was recorded five months before on 2015-09-14, but it was not reported publicly before they were sure it was a real signal. It seems that Randall knew in advance about this announcement because this comic was published on a Thursday, not following the normal publish schedule, to coincide with the announcement, and there were no other comic released Friday that week. (The altered schedule could be viewed as a meta-reference to the warping of spacetime). This is the second time within a month that a new astronomical announcement (of something discovered months before the actual announcement) has resulted in a related comic. The first being 1633: Possible Undiscovered Planets.
From the patterns in the gravitational waves detected by this instrument, it might be possible to guess the nature of the event. (e.g. two bodies with dissimilar masses circling a fixed point, two bodies with equal mass circling each other, collision of two massive bodies, etc.) It might also be possible to triangulate the location of the event. Based on these two facts (the location and nature of the event) we might be able to determine which astronomical bodies caused this event (and the status of those bodies afterwards). Thus, it provides an additional medium to observe the universe in addition to telescopes observing all kinds of electromagnetic radiation. This new medium might enable us to observe properties that we couldn't observe with the rest of our observation instruments.
However, the scientists in this comic appear to be receiving more than the expected signals from black hole collisions, they also receive gravitational spam messages, such as invitations from Linkedin, a mortgage offer, and an announcement of a social meet-up, rather than observing astronomical events. (See table below).
There is also a joke on the social meet-up's use of the word local group because the 'Local Group' is also the technical name for the group of galaxies containing the Milky Way.
It is not clear if these so called "events" are causing gravitational waves to be generated or if something, perhaps an alien civilization, is encoding spam messages in gravitational waves. It is plausible that aliens are using gravity waves to encode their messages, as we do something similar with electromagnetic waves to encode and send our messages. However, it would take an extremely advanced civilization to achieve gravity wave encoding. It requires the controlling of orbits and oscillations of super-massive bodies like the Sun, or more likely bodies ten times more massive than it. For example, the first event detected, both in this comic and in real life, was a merger of two black holes of roughly 30 solar masses each.
The title text makes the speculation, that something is sending spam encoded in gravity waves, seem more plausible, as it follows up with a joke that the message senders have gone to such a length that they caused the most energetic event recorded ever (perhaps on the scale of a few supernovae or black hole collisions). One of the scientists is so impressed with this effort that he suggests that they actually post a reply, but one of the other person declines with a "Nah"! (As you should always do with spam, else you will just encourage the sender by making it clear that there actually is a receiver on this address).
 Gravitational waves
A gravitational wave detector is a device used to measure gravitational waves, small distortions of spacetime that were first predicted by Albert Einstein in 1916. Gravitational waves are ripples in the spacetime fabric itself.
In layman terms, a gravitational wave is like moving a stone through water while partly submerged. It will cause waves on the surface of the water as it moves through it. These waves will spread away from the center of disturbance and as they move, they will cause the water molecules to oscillate around their mean positions. Similar waves are created in the space-time fabric when two celestial bodies interact with each other. If you concentrate on an area of the fabric far away from the point of disturbance, it can be observed that if the wave causes compression in one direction, it'll cause expansion of the fabric in the other. See this page for nice animations....MORE
Explanation of observed events
Event Explanation Black hole merger in Carina (30 M☉, 30 M☉) Possibly legitimate result from the gravitational wave detector. M☉ means 1 Solar Mass (1.98892×1030 kg). So the statement means that two black holes, each one 30 times more massive than our Sun were observed merging in the Carina constellation. This observation is similar to the one actually reported in the announcement on the day of this comic, were the two black holes had masses of 36 and 29 solar masses (with a uncertainty that meant they could have had masses as close as 32 and 30 solar masses vs the 30+30 in this event). Also the location of the event matches with Carina. Although at present time it is not possible to pinpoint the location of the event (that will need more detectors spread out across Earth) they still manage to find out that it most likely originated in the Southern Celestial Hemisphere, which is also where the Carina constellation is located.
Zorlax the Mighty would like to connect on Linkedin A typical LinkedIn request. As this may be a message encoded in gravitational waves, it either means that LinkedIn has now grown outside the Earth, or that the Zorlax person would like to contact Earth. Zorlax is likely a reference to a kid's television gameshow, based on time travel, Zorlax and the Time Travellers. The first sentence in the movie is: Four billions of years ago in the Earths core, destined to be the master of time he is the Mighty Zorlax. It is likely someone with the power over time would be able to create gravitational waves at his own leisure....