What the study found
The study found 19 optical nuclear transients in Zwicky Transient Facility (ZTF) data, including nine in passive galaxies, eight in active galactic nuclei (AGNs, galaxies with actively feeding central black holes), and two with uncertain host activity. The authors also identified two newly discovered repeating tidal disruption event (TDE) candidates, one exceptionally long-lived event lasting more than 5 years, and three flares in active galaxies that were brighter than absolute g-band magnitude -24.
Why the authors say this matters
The authors say these findings show the potential of their detection system for future discoveries and the value of archival searches for finding overlooked transients. They also conclude that the sample highlights concerns and areas for improvement in current and future classifiers used for transient detection.
What the researchers tested
The researchers developed an early detection system for TDEs in ZTF data as part of an alert broker, then used it during development and on the existing archive to find optical transients. For each transient, they gathered optical and infrared archival photometry from ZTF, WISE, and Catalina and assessed prior nuclear activity in the host galaxy. They also fitted the ZTF light curves with both a phenomenological model and a physically motivated model.
What worked and what didn't
The search recovered 19 optical nuclear transients and uncovered several notable cases, including two repeating TDE candidates and one object that turned out to be two separate supernovae in the same galaxy rather than a single repeating source. The study also notes that, without spectral follow-up, definitive classification of most transients is difficult, and some may instead be powered by AGN variability.
What to keep in mind
The abstract states that the lack of spectral follow-up limits definitive classification for most of the transients. It also indicates that some objects may be explained by AGN variability, so the identifications remain uncertain for part of the sample.
Key points
- Nineteen optical nuclear transients were reported from ZTF data.
- Two newly discovered repeating TDE candidates were identified.
- One transient lasted more than 5 years in a previously passive galaxy.
- Three flares in active galaxies were brighter than absolute g-band magnitude -24.
- One apparently repeating object was actually two separate supernovae in the same galaxy.
Disclosure
- Research title:
- Archive search finds 19 optical nuclear transients
- Image credit:
- Photo by Markus Winkler on Pexels
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