IRSA - ZTF Lightcurve Queries

ZTF Lightcurve Queries

Overview

IRSA provides access to the ZTF collection of lightcurve data through an application program interface (API). Search, restriction, and formatting parameters are specified in an HTTP URL. The output is a table in the requested format containing lightcurve data satisfying the search constraints.

Access Control: This section provides instructions and examples for accessing proprietary ZTF data.

Query

An IRSA ZTF-LC-API query returns a table (by default, a VOTable) containing lightcurve data corresponding to a set of ZTF objects and perhaps satisfying additional constraints. The query must specify, directly or indirectly, a set of ZTF objects for which lightcurve data is requested. In addition, it may specify the collection of ZTF lightcurve data files from which lightcurve data is to be retrieved, and it may indicate that only lightcurve data meeting certain restrictions is requested. Finally, the query may specify the format of the output.

IRSA ZTF-LC-API queries take the form of HTTP URLs whose parameters express the relevant requirements and constraints.

Parameter Purpose Parameter Name
Specify ZTF objects by their identifiers ID
Specify ZTF objects by position and other constraints POS or CIRCLE, BAND, BANDNAME, NOBS_MIN, MAG
Restrict lightcurve data TIME, BAD_CATFLAGS_MASK
Specify collection of ZTF lightcurve files COLLECTION
Specify format of output table FORMAT

These parameters are described individually below.

Behind the scenes

Typically there are multiple lightcurves for a given source position. Lightcurves are tagged in the ZTF lightcurve files by object identifier. As mentioned above, lightcurves corresponding to specific identifiers may be retrieved using the ZTF-LC-API via the ID parameter. Alternatively, this API also supports the retrieval of all lightcurves meeting positional and other constraints. When such constraints are supplied, a preliminary TAP query extracts the identifiers of all objects meeting those constraints from the ZTF objects table. Lightcurves corresponding to these identifiers are then retrieved from the ZTF lightcurve collection.

Sample queries


Query Parameters

IRSA ZTF-LC-API queries are expressed as URLs. Names of supported query parameters and syntax of their values follow guidelines from the VO spec for SIA2, which are compatible with DALI and DataLink. In particular, elements of multi-element parameter values are separated by a single space. Ranges are represented by space-separated lower and upper bounds. Unrestricted lower (resp. upper) bounds are represented by the values -Inf (resp. Inf).