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A Mildly Relativistic Outflow from the Energetic, Fast-rising Blue Optical Transient CSS161010 in a Dwarf Galaxy

D. L. CoppejansCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]R. MarguttiCIFAR Azrieli Global Scholars program, CIFAR, Toronto, CanadaG. TerreranCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]A. J. NayanaDepartment of Physics, United Arab Emirates University, Al-Ain, 15551, UAEEric R. CoughlinDepartment of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USAT. LaskarDepartment of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UKK. D. AlexanderCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]M. F. BietenholzDepartment of Physics and Astronomy, York University, Toronto, M3J 1P3, Ontario, CanadaD. CaprioliDepartment of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USAP. ChandraNational Centre for Radio Astrophysics, Tata Institute of Fundamental Research, P.O. Box 3, Pune, 411007, IndiaM. R. DroutDepartment of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario, M5S 3H4, CanadaD. FrederiksIoffe Institute, Polytekhnicheskaya, 26, St. Petersburg, 194021, RussiaC. FrohmaierInstitute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UKK. HurleyUniversity of California at Berkeley, Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720, USAC. S. KochanekCenter for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USAMorgan MacLeodCenter for Astrophysics—Harvard and Smithsonian, 60 Garden Street, Cambridge, MA 02138, USAAaron MeisnerNSF’s National Optical-Infrared Astronomy Research Laboratory, 950 N Cherry Ave, Tucson, AZ 85719, USAP. NugentLawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USAA. RidnaiaIoffe Institute, Polytekhnicheskaya, 26, St. Petersburg, 194021, RussiaDavid SandSteward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USAD. SvinkinIoffe Institute, Polytekhnicheskaya, 26, St. Petersburg, 194021, RussiaC. WardDepartment of Astronomy, University of Maryland, College Park, MD 20742, USAS. YangDepartment of Physics, University of California, 1 Shields Avenue, Davis, CA 95616-5270, USAA. BaldeschiCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]I. V. ChilingarianCenter for Astrophysics—Harvard and Smithsonian, 60 Garden Street, Cambridge, MA 02138, USAY. DongDepartment of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USAC. EsquiviaCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]Wen‐fai FongCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]C. GuidorziDepartment of Physics and Earth Science, University of Ferrara, via Saragat 1, I-44122, Ferrara, ItalyPeter LundqvistDepartment of Astronomy, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, SwedenD. MilisavljevicDepartment of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USAK. PatersonCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]D. ReichartDepartment of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USAB. J. ShappeeInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAM. C. StrohCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; [email protected]Stefano ValentiDepartment of Physics, University of California, 1 Shields Avenue, Davis, CA 95616-5270, USAB. A. ZaudererNational Science Foundation, 2415 Eisenhower Ave., Alexandria, VA 22314, USABing ZhangDepartment of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA

2020en

ABI

Аннотация

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 ( L x ∼ 5 × 10 39 erg s −1 ) and radio ( L ν ∼ 10 29 erg s −1 Hz −1 ) 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 Γ βc ≥ 0.55 c at ∼100 days. This is faster than the non-relativistic AT 2018cow (Γ βc ∼ 0.1 c ) and closer to ZTF18abvkwla (Γ βc ≥ 0.3 c at 63 days). The inferred initial kinetic energy of CSS161010 ( E k ≳ 10 51 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 ( ). 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 dwarf galaxy with stellar mass M * ∼ 10 7 M ⊙ and specific star formation rate sSFR ∼ 0.3 Gyr −1 . This mass is 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 (rate < 0.4% of the local core-collapse supernova rate) H-rich transients that can launch mildly relativistic outflows.

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DOI: 10.3847/2041-8213/ab8cc7

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