Physics & Astronomy Faculty Publications Physics and Astronomy 5-26-2020 A Mildly Relativistic Outflow from the Energentic, Fast-rising Blue Optical Transient CSS161010 in a Dwarf Galaxy Deanne L. Coppejans Northwestern University, [email protected] R. Margutti CIFAR G. Terreran Northwester University A. J. Nayana United Arab Emirates University Follow this and additional works at: https://digitalscholarship.unlv.edu/physastr_fac_articles E. R. P arCoughlint of the Cosmology , Relativity, and Gravity Commons, External Galaxies Commons, and the Stars, Princeton University Interstellar Medium and the Galaxy Commons RepositSee nextor pagey Citation for additional authors Coppejans, D. L., Margutti, R., Terreran, G., Nayana, A. J., Coughlin, E. R., Laskar, T., Alexander, K. D., Bietenholz, M., Caprioli, D., Chandra, P., Drout, M. R., Frederiks, D., Frohmaier, C., Hurley, K. H., Kochanek, C. S., MacLeod, M., Meisner, A., Nugent, P. E., Ridnaia, A., Sand, D. J., Svinkin, D., Ward, C., Yang, S., Baldeschi, A., Chilingarian, I. V., Dong, Y., Esquivia, C., Fong, W., Guidorzi, C., Lundqvist, P., Milisavljevic, D. (2020). A Mildly Relativistic Outflow from the Energentic, Fast-rising Blue Optical Transient CSS161010 in a Dwarf Galaxy. Astrophysical Journal Letters, 895(1), 1-15. http://dx.doi.org/10.3847/2041-8213/ab8cc7 This Article is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Article in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Article has been accepted for inclusion in Physics & Astronomy Faculty Publications by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. Authors Deanne L. Coppejans, R. Margutti, G. Terreran, A. J. Nayana, E. R. Coughlin, T. Laskar, K. D. Alexander, M. Bietenholz, D. Caprioli, P. Chandra, M. R. Drout, D. Frederiks, C. Frohmaier, K. H. Hurley, C. S. Kochanek, M. MacLeod, A. Meisner, P. E. Nugent, A. Ridnaia, D. J. Sand, D. Svinkin, C. Ward, S. Yang, A. Baldeschi, I. V. Chilingarian, Y. Dong, C. Esquivia, W. Fong, C. Guidorzi, P. Lundqvist, and D. Milisavljevic This article is available at Digital Scholarship@UNLV: https://digitalscholarship.unlv.edu/physastr_fac_articles/530 The Astrophysical Journal Letters, 895:L23 (15pp), 2020 May 20 https://doi.org/10.3847/2041-8213/ab8cc7 © 2020. The American Astronomical Society. All rights reserved. A Mildly Relativistic Outflow from the Energetic, Fast-rising Blue Optical Transient CSS161010 in a Dwarf Galaxy D. L. Coppejans1 , R. Margutti1,2,36 , G. Terreran1 , A. J. Nayana3,4 , E. R. Coughlin5 , T. Laskar6 , K. D. Alexander1,37 , M. Bietenholz7,8 , D. Caprioli9 , P. Chandra4 , M. R. Drout10,11 , D. Frederiks12 , C. Frohmaier13 , K. H Hurley14 , C. S. Kochanek15,16 , M. MacLeod17 , A. Meisner18 , P. E. Nugent19 , A. Ridnaia12, D. J. Sand20 , D. Svinkin12 , C. Ward19,21, S. Yang22,23,24 , A. Baldeschi1, I. V. Chilingarian17,25 , Y. Dong30 , C. Esquivia1,26, W. Fong1 , C. Guidorzi27 , P. Lundqvist28,29 , D. Milisavljevic30 , K. Paterson1 , D. E. Reichart31 , B. Shappee32 , M. C. Stroh1 , S. Valenti22 , B. A. Zauderer33,34, and B. Zhang35 1 Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected] 2 CIFAR Azrieli Global Scholars program, CIFAR, Toronto, Canada 3 Department of Physics, United Arab Emirates University, Al-Ain, 15551, UAE 4 National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, P.O. Box 3, Pune, 411007, India 5 Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA 6 Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK 7 Hartebeesthoek Radio Observatory, P.O. Box 443, Krugersdorp, 1740, South Africa 8 Department of Physics and Astronomy, York University, Toronto, M3J 1P3, Ontario, Canada 9 Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA 10 Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario, M5S 3H4, Canada 11 The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101, USA 12 Ioffe Institute, Polytekhnicheskaya, 26, St. Petersburg, 194021, Russia 13 Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK 14 University of California at Berkeley, Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720, USA 15 Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USA 16 Department of Astronomy Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA 17 Center for Astrophysics—Harvard and Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA 18 NSF’s National Optical-Infrared Astronomy Research Laboratory, 950 N Cherry Ave, Tucson, AZ 85719, USA 19 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA 20 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA 21 Department of Astronomy, University of Maryland, College Park, MD 20742, USA 22 Department of Physics, University of California, 1 Shields Avenue, Davis, CA 95616-5270, USA 23 INAF Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy 24 The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden 25 Sternberg Astronomical Institute, M. V. Lomonosov Moscow State University, 13 Universitetsky prospect, Moscow, 119234, Russia 26 Hamilton College, 198 College Hill Road, Clinton, NY 13323, USA 27 Department of Physics and Earth Science, University of Ferrara, via Saragat 1, I-44122, Ferrara, Italy 28 Department of Astronomy, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden 29 The Oskar Klein Centre, AlbaNova, SE-10691 Stockholm, Sweden 30 Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USA 31 Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA 32 Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA 33 National Science Foundation, 2415 Eisenhower Ave., Alexandria, VA 22314, USA 34 Neils Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen, Denmark 35 Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA Received 2020 March 25; revised 2020 April 23; accepted 2020 April 23; published 2020 May 26 Abstract We present X-ray and radio observations of the Fast Blue Optical Transient CRTS-CSS161010 J045834 −081803 (CSS161010 hereafter) at t=69–531 days. CSS161010 shows luminous X-ray (Lx∼5× 39 −1 29 −1 −1 10 erg s ) and radio (Lν∼10 erg s Hz ) emission. The radio emission peaked at ∼100 days post- transient explosion and rapidly decayed. We interpret these observations in the context of synchrotron emission from an expanding blast wave. CSS161010 launched a mildly relativistic outflow with velocity Γβc 0.55c at ∼100 days. This is faster than the non-relativistic AT 2018cow (Γβc∼0.1c) and closer to ZTF18abvkwla 51 (Γβc 0.3c at 63 days). The inferred initial kinetic energy of CSS161010 (Ek10 erg) is comparable to that of long gamma-ray bursts, but the ejecta mass that is coupled to the mildly relativistic outflow is significantly larger (~0.01– 0.1 M). This is consistent with the lack of observed γ-rays. The luminous X-rays were produced by a different emission component to the synchrotron radio emission. CSS161010 is located at ∼150 Mpc in a 7 −1 dwarf galaxy with stellar mass M*∼10 Me and specific star formation rate sSFR∼0.3 Gyr .Thismassis among the lowest inferred for host galaxies of explosive transients from massive stars. Our observations of CSS161010 are consistent with an engine-driven aspherical explosion from a rare evolutionary path of a H-rich stellar progenitor, but we cannot rule out a stellar tidal disruption event on a centrally located intermediate-mass black hole. Regardless of the physical mechanism, CSS161010 establishes the existence of a new class of rare 36 Alfred P. Sloan Fellow. 37 Einstein Fellow. 1 The Astrophysical Journal Letters, 895:L23 (15pp), 2020 May 20 Coppejans et al. (rate<0.4% of the local core-collapse supernova rate) H-rich transients that can launch mildly relativistic outflows. Unified Astronomy Thesaurus concepts: Supernovae (1668); Accretion (14); Black holes (162); X-ray transient sources (1852); Radio transient sources (2008) Supporting material: machine-readable table 1. Introduction in Section 3 we infer the blast wave properties based on the radio and X-ray observations. In Sections 4 and 5 we Fast Blue Optical Transients (FBOTs), or alternatively Fast respectively model the host properties and discuss models for Evolving Luminous Transients, are a class of transients defined by CSS161010. Conclusions are drawn in Section 6. The optical an extremely rapid rise to maximum light (typically < ) ( 43 −1) observations and spectral evolution will be presented in 12 days , luminous optical emission 10 erg s , and blue S. Dong et al. (2020, in preparation). Time is reported relative colors. Due to their fast rise-times, they are difficult to detect and ( fi to the estimated explosion date MJD 57667 2016 October 6; have only been identi ed as a class since the recent advent of S. Dong et al. 2020, in preparation).1σ uncertainties are high-cadence optical surveys. Only a few tens of systems have ( σ2 ( reported unless stated otherwise where is the variance of the been found at optical wavelengths e.g., Matheson et al. 2000; underlying statistical distribution). Ofek et al. 2010; Poznanski et al. 2010; Drout et al.