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.
  • Automated object classification based on light curve features.
  • Personal watchlists with daily email digests (sign-in required).
  • Favorites and object collections (sign-in required).

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.
class
POI Broker Object Classification.

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 (three cutouts showing a 1×1 arcmin area.)
  • 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

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 diagram of the moon's position according to the latitude of the observer.

Light Curve Features

Features are derived properties of light curves, usually calculated by statistics.
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.

Object Classification

Our machine learning classification system analyzes light curve features to automatically categorize astronomical objects. The feature-based classification relies on periodicity, amplitude variations, and morphological characteristics.

The classification helps astronomers prioritize follow-up observations by identifying potentially interesting objects such as eclipsing binaries, pulsating variables, or transient events. Classifications are updated as new data becomes available, providing an evolving understanding of each object's nature.

Currently, the classifier distinguishes the following classes:

cvnova
Cataclysmic variables and novae
e
Eclipsing binary stars
lpv
Long-periodic variables
puls
Pulsating variable stars (such as RR Lyrae, Mira, Cepheids)
periodic_other
Other periodic variable objects
quas
Quasars, QSOs
sn
Supernovae
yso
Young stellar objects

Advanced Features (Sign-in Required)

Watchlists & Daily Email Digests

Create personalized watchlists using our visual query builder to monitor specific astronomical objects or classes of interest. Define custom search criteria and receive daily email notifications containing links to new alerts that match your watchlist criteria from the previous 24 hours (UTC).

This feature helps tracking specific types of variable stars or following objects with certain light curve characteristics.

Favorites & Object Collections

Mark interesting astronomical objects as favorites and organize them into custom groups for easy reference. Your favorites are accessible from your profile page, allowing you to quickly return to objects of particular interest without having to remember their IDs or search criteria.

This is especially useful for maintaining collections of objects for follow-up observations, research projects, or educational purposes.

Saved Filter Bookmark

Save and reuse your custom table filters to quickly access specific sets of astronomical objects from your profile page. This feature allows you to maintain custom search criteria across different sessions.

Additional User Features

  • Personal Profile: Manage your account settings, view your watchlists, and access your favorite objects.
  • Data Export: Download light curve data, features, and individual alerts including their classification information for further analysis.

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.