Find outbursts from my watchlist

Once you have made a watchlist, you may be interested in being notified whenever something unusual – outburst for example – happens to one of your sources. Thus we combine a watchlist with a query on magnitude that detects fast rise. For the watch list see, and for the query we utilise the moving averages of apparent magnitudes that Lasair provides. See this paper for more information.

For this example, we use a watchlist of 56 AM CVn stars, which are binaries of compact object (eg white dwarf) with a very short orbit – less than an hour. This screenshot shows a recent crossmatch of the watchlist with ZTF.


This is the active query, that builds a Kafka stream, and joins the object table with the watchlist shown above. The selection criterion at the bottom looks for a magnitude difference between the 2-day moving average (latest_dc_mag_g02), and the 28-day moving average (latest_dc_mag_g28), and requires a difference of at least 0.5 magnitude in both g and r.


Here is some output from the query in a period of 6 days. The same object appears several times (SDSS J1240-0159).




We see in the light curve the brightening by 5 magnitudes. Make sure you select the “Apparent Magnitude”, which are more more suitable for variable star work.