Welcome to JOLTEON: the JOint Lensed Transient Events Observation Network!
Update X Feb, 2026: Imminent
The JOint Lensed Transients Events Observation Network (Jolteon) is a collaborative community challenge aiming to develop and test methods for identifying gravitationally lensed transients discovered with the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST). Strongly lensed transients enable many novel studies, including redshift evolution of transients, early-time lightcurve evolution and independent local measures of cosmological parameters, utilising their magnified and multiply-imaged nature. LSST will be the key to almost all lensed transient discoveries over the next decade, so there is precedence to test detection methods prior to the survey.
Jolteon will facilitate lensed transient discovery with LSST by releasing a dataset containing simulated photometric data of a broad set of common optical transients, including a subset of lensed sources for the community to uncover. The challenge will take place in three stages, each releasing different data products representative of what LSST will provide: the first stage will consist of full realistically-cadenced lightcurves, with successive stages including images as well as alert packets.
Jolteon builds on the ELAsTiCC2 dataset, which currently only contains lensed supernovae with resolved multiple images. Most lensed systems detected by LSST are too compact to be individually resolved, so we will expand to unresolved/“blended” lensed supernova systems, as well as to include other rarer flavours of lensed transient such as kilonovae, tidal disruption events (TDEs), and any additional objects as informed by the interest of the community.
For discussion or questions about the challenge, use the #sl-transient-search-challenge channel on the LSSTC Slack.
There is a github repository for Jolteon-related code and information: LSST-strong-lensing/jolteon.
Below we describe some key science goals that we aim to explore with Jolteon. Note that this list is not exhaustive!
All names are given in alphabetical order.
JOLTEON Leadership: Ana Sainz de Murieta (U. of Portsmouth), Erin Hayes (IoA/KICC), Jacob Osman Hjortlund (Stockholm), Dan Ryczanowski (U. of Portsmouth), and Luke Weisenbach (U. of Portsmouth)
JOLTEON Community Members: Anindya Ganguly, Prajakta Mane
The JOLTEON Challenge has now begun! All lensed transient classifications should be submitted to the JOLTEON leadership team by 31 April, 2026. For full details about the JOLTEON data set and how to participate in the challenge, please see our phase 1 data release note. If you have any further questions, feel free to contact the JOLTEON leadership team at: jolteon@googlegroups.com, or on the Discovery Alliance Slack.
We make the Jolteon data set available on NERSC at: /global/cfs/cdirs/lsst/www/jolteon/data/FINAL2/. In addition, a zipped version of the data can be downloaded by clicking this link.
We provide tutorials on how to access and use the JOLTEON data, which is given as SNANA FITS files. See this example jupyter notebook from the Jolteon Github to learn how to access and use these files on NERSC.
The JOLTEON Challenge relies on the ELAsTiCC data sets for light curves of contaminant objects, such as unlensed SNe and quasars. For more information about ELAsTiCC, see the challenge home page.
The ELAsTiCC and ELAsTiCC2 data sets each include SNANA simulated photometry of ~4 million transient and variable objects. Some objects (AGN, especially variable stars) are underrepresented, as the focus of ELAsTiCC was photometric identification of different types of transients. The ELAsTiCC2 data set includes ~50 million detections (“sources”) and ~400 million photometry points (“forced sources” - some of which are redundant with sources). The simulation was phtometry-level simulation, not a pixel-level simulation, so there is no pixel data, and there is no simulated uncertainty on RA and Dec of detected objects. Host galaxies were simulated, and each object includes zero to two possible hosts.
In most cases, you will want to use the ELAsTiCC2 data set. It uses a more current simulated LSST cadence (baseline 3.2, including a rolling cadence in years 2-3, and including DDF fields), and some models were updated between ELAsTiCC and ELAsTiCC2.
The full ELAsTiCC2 data set can be found at NERSC: /global/cfs/cdirs/desc-td/ELASTICC2 or can be downloaded from the challenge home page (linked above). For a tutorial on how to access and use these files on NERSC, see this example notebook from the Jolteon Github.
As the Jolteon Challenge is still ongoing, we do not yet have results to present. Stay tuned for updates on the challenge soon!