Developing consensus: How can we identify likely extragalactic transients using fields in the alert packet?

Science Alerts & Brokers
#1

There are fields in the latest LSST alert schema that are relevant in associating transients with their potential host galaxy:

  • nearbyObj “Id of the closest nearby object[s, 1-3].”
  • nearbyObjDist “Distances to nearbyObj[1-3].”
  • nearbyObjLnP “Natural log of the probability that the observed diaObject is the same as the nearbyObj[1-3].”

Is there a recommended way to identify likely extragalactic transients using these fields (and potentially additional fields in the alert packet)? In the case of ZTF alert data, an example on how to do this is publicly provided.

#2

Not yet. We aren’t able to populate those fields until after the first data release.

#3

HI Chris
Lasair has added value that may help your science: it provides the Sherlock crossmatch engine that matches many existing catalogs, including Panstarrs, DELVE and Gaia, see explanation here and notebook here. Lasair also provides lightcurve features designed to find fast blue risers, and allows filtering on absolute magnitude, see here for how to build an example filter.
Roy