An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz

Journal Article · Mon Oct 12 00:00:00 EDT 2020 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/staa2824· OSTI ID:1671851

Nicholl, M.  ^[1]; Wevers, T.  ^[2]; Oates, S. R.  ^[3]; Alexander, K. D. ^[4]; Leloudas, G. ^[5]; Onori, F.  ^[6]; Jerkstrand, A. ^[7]; Gomez, S. ^[8]; Campana, S. ^[9]; Arcavi, I. ^[10]; Charalampopoulos, P. ^[5]; Gromadzki, M. ^[11]; Ihanec, N. ^[11]; Jonker, P. G. ^[12]; Lawrence, A.  ^[13]; Mandel, I.  ^[14]; Schulze, S.  ^[15]; Short, P.  ^[13]; Burke, J. ^[16]; McCully, C. ^[16] ; Hiramatsu, D. ^[16]; Howell, D. A. ^[16]; Pellegrino, C. ^[16]; Abbot, H. ^[17]; Anderson, J. P. ^[18]; Berger, E. ^[8]; Blanchard, P. K. ^[4]; Cannizzaro, G.  ^[12]; Chen, T-W ^[19]; Dennefeld, M. ^[20]; Galbany, L.  ^[21]; González-Gaitán, S.  ^[22]; Hosseinzadeh, G. ^[8]; Inserra, C.  ^[23]; Irani, I. ^[15]; Kuin, P.  ^[24]; Müller-Bravo, T.  ^[25]; Pineda, J. ^[26]; Ross, N. P.  ^[13]; Roy, R. ^[27]; Smartt, S. J. ^[28]; Smith, K. W. ^[28]; Tucker, B. ^[17]; Wyrzykowski, Ł. ^[11]; Young, D. R. ^[28]

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1. Birmingham Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill EH9 3HJ, UK
2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
3. Birmingham Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
4. Center for Interdisciplinary Exploration and Research in Astrophysics and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3112, USA
5. DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Kgs. Lyngby, Denmark
6. Istituto di Astrofisica e Planetologia Spaziali (INAF), Via Fosso del Cavaliere 100, I-00133 Roma, Italy
7. Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Str. 1, D-85748 Garching, Germany, Department of Astronomy, Stockholm University, The Oskar Klein Centre, AlbaNova, SE-106 91 Stockholm, Sweden
8. Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138-1516, USA
9. INAF-Osservatorio Astronomico di Brera, via Bianchi 46, I-23807 Merate (LC), Italy
10. The School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, CIFAR Azrieli Global Scholars program, CIFAR, 661 University Ave. Suite 505, Toronto, ON M5G 1M1, Canada
11. Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, PL-00-478 Warszawa, Poland
12. Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, NL-6500 GL Nijmegen, the Netherlands, SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, NL-3584 CA Utrecht, the Netherlands
13. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill EH9 3HJ, UK
14. Birmingham Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK, Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia, The ARC Center of Excellence for Gravitational Wave Discovery–OzGrav, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122, Australia
15. Department of Particle Physics and Astrophysics, Weizmann Institute of Science, 234 Herzl St, Rehovot 76100, Israel
16. Las Cumbres Observatory, 6740 Cortona Dr, Suite 102, Goleta, CA 93117-5575, USA, Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
17. The Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2601, Australia
18. European Southern Observatory, Alonso de Coŕdova 3107, Vitacura, Casilla 190001, Santiago, Chile
19. Department of Astronomy, Stockholm University, The Oskar Klein Centre, AlbaNova, SE-106 91 Stockholm, Sweden
20. Institute of Astrophysics Paris (IAP), and Sorbonne University, 98bis Boulevard Arago, F-75014 Paris, France
21. Departamento de Física Teórica y del Cosmos, Universidad de Granada, E-18071 Granada, Spain
22. CENTRA-Centro de Astrofísica e Gravitação and Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, P-1049-001 Lisboa, Portugal
23. School of Physics & Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
24. Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
25. School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
26. Departamento de Ciencias Fisicas, Universidad Andrés Bello, Avda. Republica 252, Santiago, Chile
27. The Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune 411007, India
28. Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK

ABSTRACT At 66 Mpc, AT2019qiz is the closest optical tidal disruption event (TDE) to date, with a luminosity intermediate between the bulk of the population and the faint-and-fast event iPTF16fnl. Its proximity allowed a very early detection and triggering of multiwavelength and spectroscopic follow-up well before maximum light. The velocity dispersion of the host galaxy and fits to the TDE light curve indicate a black hole mass ≈106 M⊙, disrupting a star of ≈1 M⊙. By analysing our comprehensive UV, optical, and X-ray data, we show that the early optical emission is dominated by an outflow, with a luminosity evolution L ∝ t2, consistent with a photosphere expanding at constant velocity (≳2000 km s−1), and a line-forming region producing initially blueshifted H and He ii profiles with v = 3000–10 000 km s−1. The fastest optical ejecta approach the velocity inferred from radio detections (modelled in a forthcoming companion paper from K. D. Alexander et al.), thus the same outflow may be responsible for both the fast optical rise and the radio emission – the first time this connection has been observed in a TDE. The light-curve rise begins 29 ± 2 d before maximum light, peaking when the photosphere reaches the radius where optical photons can escape. The photosphere then undergoes a sudden transition, first cooling at constant radius then contracting at constant temperature. At the same time, the blueshifts disappear from the spectrum and Bowen fluorescence lines (N iii) become prominent, implying a source of far-UV photons, while the X-ray light curve peaks at ≈1041 erg s−1. Assuming that these X-rays are from prompt accretion, the size and mass of the outflow are consistent with the reprocessing layer needed to explain the large optical to X-ray ratio in this and other optical TDEs, possibly favouring accretion-powered over collision-powered outflow models.

• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
• Grant/Contract Number: CRISP PTDC/FIS-AST-31546; UIDB/00099/2020
• OSTI ID: 1671851
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Vol. 499 Journal Issue: 1; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English