Point of Interest Broker

Analyzing variable star light curves for the astronomical community.

Frequently Asked Questions

What is the Point of Interest (POI) Broker?

The Point of Interest broker is a future LSST alert broker currently operating as a prototype with ZTF.

The POI broker aims to collect and analyze variable star light curves and how their properties evolve over time.
We ingest alerts from the ZTF/LSST survey to provide:

  • Complete light curves.
  • Changes in light curve parameters (features).
  • Cross-matches to other astronomical surveys.
  • An integrated observation planning tool.

Technical: POI is a downstream broker from ANTARES, specifically processing alerts identified as high_amplitude_variable_star_candidate_staging.

More information on brokers is available at the Vera C. Rubin Observatory website .

User Guide & Reference

Descriptions of Table Values

date
The date of the alert.
alert_id
ZTF transient candidate, unique to an alert.
ztf_object_id
Unique ZTF identifier; appears in all alerts for this astronomical object.
mjd
Observation time at start of exposure (in Modified Julian Date).
ant_passband
Filter name (g, R, i) derived from ZTF fid (1, 2, 3).
ra / dec
Right Ascension and Declination (J2000 deg).
ant_mag_corrected
Magnitude from PSF-fit photometry measured from difference image, obtained from ANTARES mag.

How do I look up data?

The main table displays the most recent alerts by default on top.
Filtering and sorting are available for all columns. You can refine your results using the following methods:

  • Search: Use the filter inputs at the top of each column.
  • Sort: Click column headers to toggle ascending/descending order.
  • Coordinates: Filter by ra and dec to find specific regions.

Using Filters

Enter values in the column headers and click Filter.

Supported filter formats include:
  • Exact Match: IDs or dates.
  • Ranges: Two numbers (e.g., 18.8 19.4).
  • Thresholds: Use >18 or <18.

Detailed Alert Views

Click the ztf_object_id in a table row to view the alert detail page, which includes:

  • Light curve plots.
  • Thumbnails (cutout images)
  • Calculated features over time (tabular data and visualizations).
  • Observing planning (Finder Chart and Planning Tool by observatory location)
  • Catalog Cross-matches of the object
  • Classification

Thumbnails:

Each alert contains three cutouts showing a 1×1 arcmin area.

Observing Planning Tool

The observing planning tool assists with planning follow-up observations. Users can choose from a list of observatories, or enter their own.
It includes a display of the moon's position according to the latitude of the observer.

Light Curve Features

Features are derived properties of light curves.
Depending on the number of observations, certain features may be excluded from calculation if the data is insufficient (i.e., too few observations).
The display is restricted to features computed for the current light curve.

As Point of Interest operates as a downstream broker for ANTARES, we utilize the features calculated by ANTARES. While ANTARES persists only the most recent set of features corresponding to the latest alert (calculated for the light curve with all the current alerts), POI maintains a history of the features.
This means, once there is a new alert for a particular object, we are adding its current set of features. This history allows for tracking how features change over time.

Further Information

What other brokers are out there?

Several groups are developing brokers to process the ZTF/LSST alert stream:

Full-Stream Alert Brokers

  • Alerce
  • AMPEL
  • ANTARES
  • Babamul
  • Fink
  • Lasair
  • Pitt-Google

Downstream Alert Brokers

  • SNAPS
  • POI: Variables

How do I cite the Point of Interest broker?

A paper is forthcoming. In the meantime, please mention the Point of Interest Broker in your paper acknowledgements.