Hello, I would like to ask about light curves. Are these going to be a product of LSST, and in which category?
As a “non-user”, I’m interested to know if for example I can extract a light curve of my (variable) object during one specific month that will be included in DR1 - or will I have to wait 2 yrs after DR1 for that?
I’m looking at an example case 8.4 in RDO-13, which says “The forced-photometry is public, but the access to the prompt products database is still restricted to the LSST Users”. It’s unclear to me if this actually means the whole light curve will be public, and when.
Hi @hku, thanks for your interest in using LSST data and for this question.
For individuals without Rubin data rights who are doing time-domain science, the recommendation is to use an alert broker to access the LSST alert stream. For difference-image sources detected with >5 sigma in the LSST data, an “alert packet” will be released to these brokers in real-time. Alert packets are world public and some brokers offer public access (there are links to the various brokers on the LSST alert brokers webpage). By using an alert broker, you could access a light curve that is composed of difference-image detections (and direct-image photometry for those same observations) for your object of interest.
However, observations for which an object is not detected in the difference-image with >5 sigma do not generate an alert. If an object fades to <5 sigma in the difference-image and never rebrightens (e.g., transients), no further alerts are generated. If an object fades to <5 sigma in the difference image and then rebrightens (e.g., variables), the future alerts will contain forced photometry for non-detection epochs in the past 12 months. To summarize, this means the “whole” light curve is not necessarily released via the alert stream and thus publicly accessible.
The statement “The forced-photometry is public, but the access to the prompt products database is still restricted to the LSST Users” is referring to the fact that forced photometry is done as part of the prompt processing pipeline which also produces alerts. This forced photometry is stored in the Prompt Products Database (PPDB), which has no proprietary period, but access to that database through the Rubin Data Access Centers is restricted to individuals with Rubin data rights.
In the annual data releases, which do have a proprietary period of two years, there will be forced photometry in the direct and difference images for all epochs at the locations of all objects detected.