Discovery and Follow-up of ASASSN-23bd (AT 2023clx): The Lowest Redshift and Least Luminous Tidal Disruption Event To Date

W. B. Hoogendam; J. T. Hinkle; B. J. Shappee; K. Auchettl; C. S. Kochanek; K. Z. Stanek; W. P. Maksym; M. A. Tucker; M. E. Huber; N. Morrell; C. R. Burns; D. Hey; T. W. -S. Holoien; J. L. Prieto; M. Stritzinger; A. Do; A. Polin; C. Ashall; P. J. Brown; J. M. DerKacy; L. Ferrari; L. Galbany; E. Y. Hsiao; S. Kumar; J. Lu; C. P. Stevens

doi:10.1093/mnras/stae1121

paper

Discovery and Follow-up of ASASSN-23bd (AT 2023clx): The Lowest Redshift and Least Luminous Tidal Disruption Event To Date

arXiv:2401.05490 · doi:10.1093/mnras/stae1121

Abstract

We report the All-Sky Automated Survey for SuperNovae discovery of the tidal disruption event (TDE) ASASSN-23bd (AT 2023clx) in NGC 3799, a LINER galaxy with no evidence of strong AGN activity over the past decade. With a redshift of $z = 0.01107$ and a peak UV/optical luminosity of $(5.4 \pm 0.4) \times 1 0^{42}$ erg s $^{- 1}$ , ASASSN-23bd is the lowest-redshift and least-luminous TDE discovered to date. Spectroscopically, ASASSN-23bd shows H $α$ and He I emission throughout its spectral time series, and the UV spectrum shows nitrogen lines without the strong carbon and magnesium lines typically seen for AGN. Fits to the rising ASAS-SN light curve show that ASASSN-23bd started to brighten on MJD 59988 $_{- 1}^{+ 1}$ , $\sim$ 9 days before discovery, with a nearly linear rise in flux, peaking in the $g$ band on MJD $6000 0_{- 3}^{+ 3}$ . Scaling relations and TDE light curve modelling find a black hole mass of $\sim$ 10 $^{6}$ $M_{⊙}$ , which is on the lower end of supermassive black hole masses. ASASSN-23bd is a dim X-ray source, with an upper limit of $L_{0.3 - 10 keV} < 1.0 \times 1 0^{40}$ erg s $^{- 1}$ from stacking all \emph{Swift} observations prior to MJD 60061, but with soft ( $\sim 0.1$ keV) thermal emission with a luminosity of $L_{0.3 - 2 keV} \sim 4 \times 1 0^{39}$ erg s $^{- 1}$ in \emph{XMM-Newton} observations on MJD 60095. The rapid $(t < 15$ days) light curve rise, low UV/optical luminosity, and a luminosity decline over 40 days of $Δ L_{40} \approx - 0.7$ make ASASSN-23bd one of the dimmest TDEs to date and a member of the growing ``Low Luminosity and Fast'' class of TDEs.

arXiv comment18 pages, 14 figures, published in MNRAS

Discovery and Follow-up of ASASSN-23bd (AT 2023clx): The Lowest Redshift and Least Luminous Tidal Disruption Event To Date

Abstract

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