A dust-enshrouded tidal disruption event with a resolved radio jet in a galaxy merger

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Science  03 Aug 2018:
Vol. 361, Issue 6401, pp. 482-485
DOI: 10.1126/science.aao4669
  • Fig. 1 The transient Arp 299-B AT1 and its host galaxy Arp 299.

    (A) A color-composite optical image from the HST, with high-resolution, 12.5 by 13 arcsec size near-IR 2.2-μm images [insets (B) and (C)] showing the brightening of the B1 nucleus (7). (D) The evolution of the radio morphology as imaged with VLBI at 8.4 GHz [7 × 7 milli-arcsec (mas) region with the 8.4-GHz peak position in 2005, right ascension (RA) = 11h28m30.9875529s, declination (Dec) = 58°33′40′′.783601 (J2000.0), indicated by the dotted lines]. The VLBI images are aligned with an astrometric precision better than 50 μas. The initially unresolved radio source develops into a resolved jet structure a few years after the explosion, with the center of the radio emission moving westward with time (7). The radio beam size for each epoch is indicated in the lower-right corner.

  • Fig. 3 Infrared properties of Arp 299-B AT1.

    (A) Evolution of the observed IR spectral energy distribution (points) shown together with blackbody fits between 136 and 4207 days after the first IR detection on 2004 Dec. 21.6 (7). Over this period, the blackbody temperature decreased from ~1050 to ~750 K, while the blackbody radius increased from 0.04 to 0.13 pc. (B) The evolution of the integrated blackbody luminosity (blue circles) and cumulative radiated energy (red squares). The observed radiated energy by day 4207 was about 1.5 × 1052 erg.

  • Fig. 2 Radio properties of Arp 299-B AT1.

    (A) Radio luminosity evolution of Arp 299-B AT1 at 1.7 (circles), 5.0 (pentagons), and 8.4 GHz (squares) spanning more than 12.1 years of observations, along with modeled radio light curves, using hydrodynamic and radiative simulations for a TDE-launched jet (16). The day zero corresponds to 2004 Dec. 21.6. (B) Intrinsic (beaming-corrected) jet kinetic energy, EK, versus outflow speed (19) [Γβ, where Γ = (1 – β2)–1/2 is the bulk Lorentz factor of the outflow and β = v/c], from radio observations of gamma-ray bursts (GRBs), supernovae (SNe), low-luminosity active galactic nuclei (LLAGN), and TDEs (4, 16, 1921, 32). The large circles show, from right to left, the inferred loci for Arp 299-B AT1 at four different epochs in the observer’s frame: just after the jet is launched by the TDE, and ~1, ~12, and ~760 days thereafter. For the LLAGN sample, we have assumed a constant jet kinetic power over 10 years. The triangles indicate upper limits for the expansion speed of IGR J1258+01 (20) and Sw J1644+57 (21).

  • Fig. 4 Model for the observed properties of Arp 299-B AT1.

    Best-fit models for the spectral energy distribution of the Arp 299 nucleus B at (A) pre-outburst and (B) post-outburst (734 days after the first IR detection). The models include a starburst component (dashed line), an active galactic nucleus (AGN) dusty torus (dotted line), and a polar dust component (thick solid line) (7). The sum of these components is shown as a thin solid line. In (B), most of the model parameters were fixed, while the temperature of the polar dust varied from 500 K in the pre-outburst case to 900 K in the post-outburst case. This yields a covering factor of the polar dust of 23 to 78%, implying that the total radiated energy is ~(1.9 to 6.5) × 1052 erg. (C) Schematic diagram (not to scale) showing the geometry of the emitting and absorbing regions (7). The TDE generates prominent x-ray, ultraviolet, and optical emission. However, the direct line of sight to the central black hole is obscured by the dusty torus, which is opaque from soft x-rays to infrared wavelengths. The polar dust reradiates in the infrared a fraction of the total energy emitted by the event. The transient radio emission originates from a relativistic jet launched by the tidal disruption of a star.

Supplementary Materials

  • A dust-enshrouded tidal disruption event with a resolved radio jet in a galaxy merger

    S. Mattila, M. Pérez-Torres, A. Efstathiou, P. Mimica, M. Fraser, E. Kankare, A. Alberdi, M. Á. Aloy, T. Heikkilä, P. G. Jonker, P. Lundqvist, I. Martí-Vidal, W. P. S. Meikle, C. Romero-Cañizales, S. J. Smartt, S. Tsygankov, E. Varenius, A. Alonso-Herrero, M. Bondi, C. Fransson, R. Herrero-Illana, T. Kangas, R. Kotak, N. Ramírez-Olivencia, P. Väisänen, R. J. Beswick, D. L. Clements, R. Greimel, J. Harmanen, J. Kotilainen, K. Nandra, T. Reynolds, S. Ryder, N. A. Walton, K. Wiik, G. Östlin

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