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Distinguishing Tidal Disruption Events from Impostors

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Abstract

Recent claimed detections of tidal disruption events (TDEs) in multi-wavelength data have opened potential new windows into the evolution and properties of otherwise dormant supermassive black holes (SMBHs) in the centres of galaxies. At present, there are several dozen TDE candidates, which share some properties and differ in others. The range in properties is broad enough to overlap other transient types, such as active galactic nuclei (AGN) and supernovae (SNe), which can make TDE classification ambiguous. A further complication is that “TDE signatures” have not been uniformly observed to similar sensitivities or even targeted across all candidates. This chapter both reviews those events that are unusual relative to other TDEs, including the possibility of TDEs in pre-existing AGN, and summarises those characteristics thought to best distinguish TDEs from continuously accreting AGN, strongly flaring AGN, SNe, and Gamma-Ray Bursts (GRBs), as well as other potential impostors like stellar collisions, “micro-TDEs,” and circumbinary accretion flows. We conclude that multiple observables should be used to classify any one event as a TDE. We also consider the TDE candidate population as a whole, which, for certain host galaxy or SMBH characteristics, is distinguishable statistically from non-TDEs, suggesting that at least some TDE candidates do in fact arise from SMBH-disrupted stars.

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Notes

  1. One possible exception is if a TDE occurs in a binary SMBH. In this case, the TDE may be perceived as recurring transient behaviour when the X-ray light dims due to the interaction with the second SMBH.

  2. The (in)ability to detect such repeated flares naturally also depends on their amplitudes, which are not necessarily as high as the flare that led to the identification of the TDE candidate.

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Acknowledgements

The authors thank ISSI for their support and hospitality and the review organisers for their leadership in coordinating these reviews. This work was performed in part at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611, during the January 2019 Aspen conference on Using Tidal Disruption Events to Study Super-Massive Black Holes. We are grateful to Sjoert van Velzen and Ryan Foley for leading a discussion there about possible differences between TDEs and supernovae. We also thank Nicholas Stone, Sixiang Wen, and Dennis Zaritsky for helpful information. AIZ acknowledges support from grant HST-GO-14717.001-A from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Incorporated, under NASA contract NAS5-26555. BT acknowledges support from the Israel Science Foundation (grant 1849/19). KAA is supported by the Danish National Research Foundation (DNRF132). JLD is supported by the GRF grant from the Hong Kong government under HKU 27305119. KDF is supported by Hubble Fellowship grant HST-HF2-51391.001-A from STScI, operated by AURA, Inc., under NASA contract NAS5-26555. TW is funded in part by European Research Council grant 320360 and by European Commission grant 730980. Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013.

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Authors and Affiliations

  1. University of Arizona, Tucson, USA

    Ann Zabludoff & Yujing Qin

  2. Tel Aviv University, Tel Aviv, Israel

    Iair Arcavi & Benny Trakhtenbrot

  3. STScI, Baltimore, USA

    Stephanie La Massa

  4. Technion, Haifa, Israel

    Hagai B. Perets

  5. National Science Foundation, Arlington, USA

    B. Ashley Zauderer

  6. University of Melbourne, Melbourne, Australia

    Katie Auchettl

  7. University of Hong Kong, Hong Kong, China

    Jane L. Dai

  8. University of Illinois, Urbana, USA

    K. Decker French

  9. University of California, Santa Cruz, USA

    Tiara Hung & Enrico Ramirez-Ruiz

  10. Massachusetts Institute of Technology, Cambridge, USA

    Erin Kara

  11. University of Milano, Milan, Italy

    Giuseppe Lodato

  12. Harvard-Smithsonian Center for Astrophysics, Cambridge, USA

    W. Peter Maksym

  13. Lawrence Livermore National Laboratory, Livermore, USA

    Nathaniel Roth

  14. Vanderbilt University, Nashville, USA

    Jessie C. Runnoe

  15. European Southern Observatory, Santiago, Chile

    Thomas Wevers

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The Tidal Disruption of Stars by Massive Black Holes

Edited by Peter G. Jonker, Sterl Phinney, Elena Maria Rossi, Sjoert van Velzen, Iair Arcavi and Maurizio Falanga

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Zabludoff, A., Arcavi, I., La Massa, S. et al. Distinguishing Tidal Disruption Events from Impostors. Space Sci Rev 217, 54 (2021). https://doi.org/10.1007/s11214-021-00829-4

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