Published April 20, 2024 | Version Published
Journal Article Open

tdescore: An Accurate Photometric Classifier for Tidal Disruption Events

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon Deutsches Elektronen-Synchrotron DESY
  • 3. ROR icon Humboldt-Universität zu Berlin
  • 4. ROR icon Space Telescope Science Institute
  • 5. ROR icon Johns Hopkins University
  • 6. ROR icon University of Maryland, College Park
  • 7. ROR icon Goddard Space Flight Center
  • 8. ROR icon Queen's University Belfast
  • 9. ROR icon Stockholm University
  • 10. ROR icon Leiden University
  • 11. ROR icon New York State Office for People With Developmental Disabilities
  • 12. ROR icon University of California, Berkeley
  • 13. ROR icon Infrared Processing and Analysis Center

Abstract

Optical surveys have become increasingly adept at identifying candidate tidal disruption events (TDEs) in large numbers, but classifying these generally requires extensive spectroscopic resources. Here we present tdescore, a simple binary photometric classifier that is trained using a systematic census of ∼3000 nuclear transients from the Zwicky Transient Facility (ZTF). The sample is highly imbalanced, with TDEs representing ∼2% of the total. tdescore is nonetheless able to reject non-TDEs with 99.6% accuracy, yielding a sample of probable TDEs with recall of 77.5% for a precision of 80.2%. tdescore is thus substantially better than any available TDE photometric classifier scheme in the literature, with performance not far from spectroscopy as a method for classifying ZTF nuclear transients, despite relying solely on ZTF data and multiwavelength catalog cross matching. In a novel extension, we use "Shapley additive explanations" to provide a human-readable justification for each individual tdescore classification, enabling users to understand and form opinions about the underlying classifier reasoning. tdescore can serve as a model for photometric identification of TDEs with time-domain surveys, such as the upcoming Rubin observatory.

Acknowledgement

We thank Adam Stein, Ludwig Rauch, and Niharika Sravan for fruitful discussions about machine-learning classification.

R.S. and M.M.K acknowledge support from grants by the National Science Foundation (AST 2206730) and the David and Lucille Packard Foundation (PI Kasliwal). M.N. is supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 948381) and by UK Space Agency grant No. ST/Y000692/1. E.K.H. acknowledges support by NASA under award number 80GSFC21M0002. S.J.N. is supported by the US National Science Foundation (NSF) through grant AST-2108402.

Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grants Nos. AST-1440341 and AST-2034437 and a collaboration including current partners Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. The Gordon and Betty Moore Foundation, through both the Data-Driven Investigator Program and a dedicated grant, provided critical funding for SkyPortal.

Facilities

PO:1.2m - Palomar Observatory's 1.2 meter Samuel Oschin Telescope (ZTF; Bellm et al. 2019), PO:1.5m (SEDm; Blagorodnova et al. 2018; Rigault et al. 2019; Kim et al. 2022)

Software References

AMPEL (Nordin et al. 2019), astropy (Astropy Collaboration et al. 2022), astroquery (Ginsburg et al. 2019), numpy (Harris et al. 2020), pandas (Wes McKinney 2010), scikit-learn (Pedregosa et al. 2011), scipy (Virtanen et al. 2020), SHAP (Lundberg & Lee 2017), sncosmo (Barbary et al. 2016), tdescore (Stein 2024), XGBoost (Chen & Guestrin 2016)

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Additional details

Identifiers

ISSN
2041-8213

Funding

National Science Foundation
AST-2206730
David and Lucile Packard Foundation
European Research Council
948381
United Kingdom Space Agency
ST/Y000692/1
National Aeronautics and Space Administration
80GSFC21M0002
National Science Foundation
AST-2108402
National Science Foundation
AST-1440341
National Science Foundation
AST-2034437
National Science Foundation
AST-1106171
Gordon and Betty Moore Foundation

Caltech Custom Metadata

Caltech groups
Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility