Discovery and follow-up of ASASSN-19dj: An X-ray and UV luminous TDE in an extreme post-starburst galaxy

Jason T. Hinkle, T. W.S. Holoien, K. Auchettl, B. J. Shappee, J. M.M. Neustadt, A. V. Payne, J. S. Brown, C. S. Kochanek, K. Z. Stanek, M. J. Graham, M. A. Tucker, A. Do, J. P. Anderson, S. Bose, P. Chen, D. A. Coulter, G. Dimitriadis, Subo Dong, R. J. Foley, M. E. HuberT. Hung, C. D. Kilpatrick, G. Pignata, A. L. Piro, C. Rojas-Bravo, M. R. Siebert, B. Stalder, Todd A. Thompson, J. L. Tonry, P. J. Vallely, J. P. Wisniewski

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


We present observations of ASASSN-19dj, a nearby tidal disruption event (TDE) discovered in the post-starburst galaxy KUG 0810+227 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d ≃ 98 Mpc. We observed ASASSN-19dj from -21 to 392 d relative to peak ultraviolet (UV)/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From the ASAS-SN g-band data, we determine that the TDE began to brighten on 2019 February 6.8 and for the first 16 d the rise was consistent with a flux α2 power law. ASASSN-19dj peaked in the UV/optical on 2019 March 6.5 (MJD = 58548.5) at a bolometric luminosity of L = (6.2 ± 0.2) × 1044 erg s-1. Initially remaining roughly constant in X-rays and slowly fading in the UV/optical, the X-ray flux increased by over an order of magnitude ∼225 d after peak, resulting from the expansion of the X-ray emitting region. The late-time X-ray emission is well fitted by a blackbody with an effective radius of ∼1 × 1012 cm and a temperature of ∼6 × 105 K. The X-ray hardness ratio becomes softer after brightening and then returns to a harder state as the X-rays fade. Analysis of Catalina Real-Time Transient Survey images reveals a nuclear outburst roughly 14.5 yr earlier with a smooth decline and a luminosity of LV ≥ 1.4 × 1043 erg s-1, although the nature of the flare is unknown. ASASSN-19dj occurred in the most extreme post-starburst galaxy yet to host a TDE, with Lick HδA = 7.67 ± 0.17 Å.

Original languageEnglish
Pages (from-to)1673-1696
Number of pages24
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 1 Jan 2021


  • Accretion
  • Accretion discs
  • Black hole physics
  • Galaxies: nuclei

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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