456.01 - AT2018cow: a luminous millimeter transient(Anna Yen Qin Ho)

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Jan 10th at 9:00 AM until 10:00 AM

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Author(s): A.Y. Ho, S. Phinney, V. Ravi, S. Kulkarni, N. Kamraj, M. Kasliwal, Caltech, Pasadena, California, UNITED STATES|S.B. Cenko, Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, UNITED STATES|V. Ravi, G. Petitpas, R. Blundell, R. Howie, T. Sridharan, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, UNITED STATES|B. Emonts, I. Yoon, National Radio Astronomy Observatory, Charlottesville, Virginia, UNITED STATES|V. Bhalerao, Department of Physics, Indian Institute of Technology Bombay, Mumbai, Virginia, INDIA|S.B. Cenko, Joint Space-Science Institute, University of Maryland, College Park, Maryland, UNITED STATES|D. Dobie, T. Murphy, Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, New South Wales, AUSTRALIA|D. Dobie, ATNF, CSIRO Astronomy and Space Science, Epping, New South Wales, AUSTRALIA|D. Perley, Astrophysics Research Institute, Liverpool John Moores University, Liverpool, New South Wales, UNITED KINGDOM|
Institution(s): 1. Caltech, Pasadena, CA, United States. 2. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, United States. 3. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States. 4. National Radio Astronomy Observatory, Charlottesville, VA, United States. 5. Department of Physics, Indian Institute of Technology Bombay, Mumbai, India. 6. Joint Space-Science Institute, University of Maryland, College Park, MD, United States. 7. Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW, Australia. 8. ATNF, CSIRO Astronomy and Space Science, Epping, NSW, Australia. 9. Astrophysics Research Institute, Liverpool John Moores University, Liverpool, United Kingdom.
Contributing team(s): SMA staff, CSIRO Astronomy and Space Science (CASS) staff, ALMA staff
We present detailed submillimeter- through centimeter-wave observations of the extraordinary extragalactic transient AT2018cow. The apparent characteristics -- the high radio luminosity, the long-lived emission plateau at millimeter bands, and the sub-relativistic velocity -- have no precedent. A basic interpretation of the data suggests Ek > 1048 erg coupled to a fast but sub-relativistic (v ≈ 0.13c) shock in a dense (ne ≈ 3×105 cm−3) medium. We find that the X-ray emission is not naturally explained by an extension of the radio-submm synchrotron spectrum, nor by inverse Compton scattering of the dominant blackbody UVOIR photons by energetic electrons within the forward shock. By Δt ≈ 20 days, the X-ray emission shows spectral softening and erratic inter-day variability. Taken together, we are led to invoke an additional source of X-ray emission: the central engine of the event. Regardless of the nature of this central engine, this source heralds a new class of energetic transients shocking a dense medium, which at early times are most readily observed at millimeter wavelengths.

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