Relevant JIRA ticket: https://jira.lsstcorp.org/browse/DM-11962
This project will also address PST-31
At some point, DM will have to select which variability characterization parameters (VCP) are included in the source catalogs (Prompt and DRP). This will depend on what is needed by the science community and by the mini-brokers, and what can be computationally supported by the DM system. Regarding the former, the TVS has a task force to evaluate which VCPs are needed for their science goals which should conclude around the end of 2018. It is anticipated that a similar selection process for VCPs as e.g., photo-z, will be needed.
STATUS: the relevant TVS task force appears to be unresponsive/dormant while the Cadence Optimization white papers are happening
LSST DM documentation relevant to VCPs.
Science Requirements Document (SRD; ls.st/srd):
- page 39: the LSST data products will included "variability information such as ... an appropriate compact description of light curves".
- page 41: "The data stream will also include prior variability information and data from the same night, if available. The prior variability information will at the very least include low-order light-curve moments and probability that the object is variable, and ideally the full light curves in all available bands."
Data Products Definitions Document (DPDD; ls.st/dpdd):
- Section 4.2.1 describes Object Characterization Parameters, which includes variability characterization (page 34): "Parameters will be provided, designed to characterize periodic and aperiodic variability features ... in each bandpass. We caution that the exact features in use when LSST begins operations are likely to be different compared to the baseline described here; this is to be expected given the rapid pace of research in time domain astronomy. However, their number is unlikely to grow beyond the present estimate."
- The DIAObject (Table 2) and Object (Table 4) catalog measurements include 'lcPeriodic', "Periodic features extracted from light-curves using generalized Lomb-Scargle periodogram (float[6x32])", and 'lcNonPeriodic', "Non-periodic features extracted from light-curves (float[6x20])". This applies to both the Prompt and DR Pipeline DIAObject table.
- In catalogs from the Prompt Pipeline, these VCPs will be based on the last ~12 months of observations, and will be updated within 60s of a new observation and issued with the Alert. In catalogs from the Data Release Pipeline, these VCPs will be based on all past observations for a given Object.
Data Management Science Pipelines Design Document (ls.st/ldm-151)
- Section 5.6.4 'Classification' (under Section 5.6 'Postprocessing') describes how the variability characterization parameters might be used for star/galaxy classification parameter, and so there may be extra constraints on which variability characterization parameters are chosen if some are particularly useful for this purpose
- Section 6.21 'Variability Characterization' (under Section 6 'Algorithmic Components') states that "lightcurve variability is characterized by providing a series of numeric summary ‘features’ derived from the lightcurve." It cites Richards et al. (2011), ApJ, 733, 1, and its two classes of features, periodic and aperiodic, and states that these parameters will be "calculated and recorded separately for each band" and saved to the Object and DIAObject catalog (as also described in the DPDD).
- Section 6.21.1 'Characterization of Periodic Variability' summarizes which parameters of Richards et al. (2011) would be stored in the 32 floats reserved for 'lcPeriodic' in the DIAObject and Object catalogs.
- Section 6.21.2 'Characterization of Aperiodic Variability' summarizes which parameters of Richards et al. (2011) would be stored in the 20 floats reserved for 'lcNonPeriodic' in the DIAObject and Object catalogs.