Mid-infrared Flare of TDE Candidate PS16dtm: Dust Echo and Implications for the Spectral Evolution

Ning Jiang, Tinggui Wang, Lin Yan, Ting Xiao, Chenwei Yang, Liming Dou, Huiyuan Wang, Roc Cutri, Amy Mainzer

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

PS16dtm was classified as a candidate tidal disruption event in a dwarf Seyfert 1 galaxy with a low-mass black hole (∼106 M) and has presented various intriguing photometric and spectra characteristics. Using the archival Wide-field Infrared Survey Explorer and the newly released NEOWISE data, we found that PS16dtm is experiencing a mid-infrared (MIR) flare that started ∼11 days before the first optical detection. Interpreting the MIR flare as a dust echo requires close pre-existing dust with a high covering factor and suggests that the optical flare may have brightened slowly for some time before it became bright detectable from the ground. More evidence is given at the later epochs. At the peak of the optical light curve, the new inner radius of the dust torus has grown to a much larger size (i.e., a factor of seven of the initial radius) due to the strong radiation field. At ∼150 days after the first optical detection, the dust temperature has dropped well below the sublimation temperature. Other peculiar spectral features shown by PS16dtm are the transient, prominent Fe II emission lines and outflows indicated by broad absorption lines detected during the optical flare. Our model explains the enhanced Fe II emission from iron that is newly released from the evaporated dust. The observed broad absorption line outflow could be explained by accelerated gas in the dust torus due to the radiation pressure.

Original languageEnglish (US)
Article number63
JournalAstrophysical Journal
Volume850
Issue number1
DOIs
StatePublished - Nov 20 2017
Externally publishedYes

Keywords

  • galaxies: active
  • galaxies: individual (PS16dtm)
  • galaxies: nuclei

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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