The Swift telescope is back in operation after being off-line since last November. The reason is that the Sun was transiting the Galactic center and its radiation interfered with observations in that direction. Now that the Sun is past this direction, Swift was able to get a new data point (red dot on the right side of the diagram). This shows that the X-ray intensity is less than 3 sigma (3 standard deviations), the upper dotted line, above the mean activity level, lower dashed line, which lies slightly above the 0.07 count/s baseline. Hence the activity is currently within reasonable range of the previous activity baseline for Sgr A* seen at the left side of the diagram. The large flare that began close to day 110 was due to magnetar SGR 1757-29 whose sky position lies very close to the Galactic center (GC). Now that this flare has subsided and the Sun is out of the way, Swift is able to see the GC's activity level once again. For more on relevance of the activity level, see update below.
The Swift website provides an email address where one can sign up to get automatic email updates of their telescope data (swift.sgra 'at' gmail.com). But, I now found out that you must be an astronomer to sign up. So for those of you out there who have published in astronomy journals, I encourage you to use this email address. For all others, be assured that I will post any notifications they send me. These will be sent out only if the Galactic core's X-ray output exceeds the 3 sigma level. There may be as much as a one day delay in receiving this data. Additional information about the Swift data can be found here: http://swift-sgra.com/ which is a link available for everyone.
Another resource that may provide up-to-date data on the Galactic center is the Astronomer's Telegram (http://www.astronomerstelegram.org). It is a place where astronomers post their latest observations on a wide range of astronomical objects. Information on the recent Swift observation is posted here: http://www.astronomerstelegram.org/?read=5847.
Yet another source to check would be readings from cosmic ray neutron monitoring stations which monitor the cosmic ray background radiation. One station is located in Athens, Greece, and their measurements for the past month can be viewed at this link: http://cosray.phys.uoa.gr.
To answer questions that were posted, I have added the following additional discussion:
If the X-ray intensity exceeds the 3 sigma level, this means that the Swift astronomers consider that the readings are significant enough to communicate to other astronomers and other interested parties (e.g., those who have signed up to receive notification emails by requesting at the email address given above). It does not necessarily mean a danger for us. Also it does not necessarily mean that such elevated X-ray emission is coming from the Galactic core. For example, the X-ray flare that occurred around day 110 instead came from a magnetar close to the core.
To take a wider perspective, since 2006 there have been six X-ray flares that likely originated from Sgr A*. These are shown in the diagram below taken from the paper of Degenaar, et al., 2013. The largest occurred in 2010 (flare #6). Its luminosity was (~3 X 1035 erg/s), or about 15 fold greater than the baseline activity level. This was a lower intensity than the magnetar flare. The other five flares ranged from 5 to 14 fold above the activity baseline. All of these exceeded the 3 sigma level which is about 3.5 fold above the baseline. Obviously, nothing earth shattering happened during these past events, so anything in this range should not be anything to worry about, even if a notification is sent out. If it were a 200 fold increase or above, then this is something to raise one's interest. To take a wild guess, levels corresponding to a superwave alert would likely have to exceed the 5,000 fold increase level.
One astronomer (Shcherbakov, 2014) feels that if the G2 cloud is just a 4 earth mass gas cloud, and if only gas and no star enters the core, then the level of activity of Sgr A* should be far below the level of the magnetar flare, hence nothing very exciting. But as I have warned in the previous posting, if this cloud contains a binary star and by chance the companion happens to crash onto the core, the consequences could be disastrous. Hopefully this will not happen.
Would we see core activity leading up to a significant event? If a star or planet were about to fall into the core there would likely be a significant rise in X-ray emission that would preceed the main rise by about 2 to 3 days. This would be due to X-ray emission given off during pre fragmentation of the star or planet when it reaches within about 30 AU of the core (see Galactic Pinball posting). This early warning would likely significantly exceed the intensity of the 2013 magnetar flare. Unfortunately, since there is a 1 day delay in Swift sending out their activity notifications, this does not give you too much of a warning. Then when impact occurs, the activity rise would be percipitous. It would come without warning similar to the sudden arrival of a gamma ray burst. The only example we have of a Galactic core turning on is our observations of the Draco galaxy located 3.8 billiion light years away. Its core emission rose to full quasar intensity within 15 minutes. For information on this see the following postings on the Starburst Superwave Forum:
Most astronomers still don't realize that they are witnessing the onset of a full blown core explosion in this Draco galaxy. The most intense emission from this Galaxy came in the first 3 days after which its intensity fell by 30 fold, but was still high enough (weaker quasar level) to be serious. This calls to mind the Fatima Prophecy warning of the 3 days of darkness.