Radio and X-Ray Observations of the Luminous Fast Blue Optical Transient AT 2020xnd

Journal Article · 16 February 2022 · The Astrophysical Journal

DOI: https://doi.org/10.3847/1538-4357/ac4506 · OSTI ID:1983220

Bright, Joe S.  ^[1]; Margutti, Raffaella  ^[1]; Matthews, David ^[1]; Brethauer, Daniel ^[1]; Coppejans, Deanne  ^[2]; Wieringa, Mark H.  ^[3]; Metzger, Brian D.  ^[4]; DeMarchi, Lindsay  ^[5]; Laskar, Tanmoy  ^[6]; Romero, Charles  ^[7]; Alexander, Kate D.  ^[5]; Horesh, Assaf  ^[8]; Migliori, Giulia  ^[9]; Chornock, Ryan  ^[10]; Berger, Edo  ^[11]; Bietenholz, Michael  ^[12]; Devlin, Mark J.  ^[13]; Dicker, Simon R.  ^[13]; Jacobson-Galán, Wynn V.  ^[1]; Mason, Brian S.  ^[14] ; Milisavljevic, Dan  ^[15]; Motta, Sara E.  ^[16]; Mroczkowski, Tony  ^[17]; Ramirez-Ruiz, Enrico  ^[18]; Rhodes, Lauren ^[19]; Sarazin, Craig L.  ^[20]; Sfaradi, Itai ^[8]; Sievers, Jonathan  ^[21]

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1. Univ. of California, Berkeley, CA (United States); Northwestern Univ., Evanston, IL (United States)
2. Northwestern Univ., Evanston, IL (United States); Univ. of Warwick, Coventry (United Kingdom)
3. Commonwealth Scientific and Industrial Research Organisation (CSIRO), Epping, NSW (Australia)
4. Columbia Univ., New York, NY (United States); Flatiron Institute, New York, NY (United States)
5. Northwestern Univ., Evanston, IL (United States)
6. Univ. of Bath (United Kingdom); Radboud Univ., Nijmegen (Netherlands)
7. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Green Bank Observatory, Green Bank, WV (United States); Univ. of Pennsylvania, Philadelphia, PA (United States)
8. Hebrew Univ. of Jerusalem (Israel)
9. Istituto Nazionale di Astrofisica (INAF), Bologna (Italy). Institute of Radio Astronomy
10. Univ. of California, Berkeley, CA (United States)
11. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
12. York Univ., Toronto, ON (Canada); South African Radio Astronomy Observatory, Krugersdorp (South Africa). Hartebeesthoek Radio Observatory
13. Univ. of Pennsylvania, Philadelphia, PA (United States)
14. National Radio Astronomy Observatory, Charlottesville, VA (United States)
15. Purdue Univ., West Lafayette, IN (United States)
16. Istituto Nazionale di Astrofisica (INAF), Merate (Italy). Osservatorio Astronomico di Brera; Univ. of Oxford (United Kingdom)
17. European Southern Observatory (ESO), München (Germany)
18. Univ. of California, Santa Cruz, CA (United States); Univ. of Copenhagen (Denmark)
19. Univ. of Oxford (United Kingdom); Max Planck Institute for Radio Astronomy, Bonn (Germany)
20. Univ. of Virginia, Charlottesville, VA (United States)
21. McGill Univ., Montreal, QC (Canada)

We present deep X-ray and radio observations of the fast blue optical transient (FBOT) AT 2020xnd/ZTF 20acigmel at z = 0.2433 from 13 days to 269 days after explosion. AT 2020xnd belongs to the category of optically luminous FBOTs with similarities to the archetypal event AT 2018cow. AT 2020xnd shows luminous radio emission reaching L_ν ≈ 8 × 10²⁹ erg s^-1 Hz^-1 at 20 GHz and 75 days post-explosion, accompanied by luminous and rapidly fading soft X-ray emission peaking at L_X ≈ 6 × 10⁴² erg s^-1. Interpreting the radio emission in the context of synchrotron radiation from the explosion's shock interaction with the environment, we find that AT 2020xnd launched a high-velocity outflow (v ~ 0.1c–0.2c) propagating into a dense circumstellar medium (effective $$\dot{M}\approx {10}^{-3}\,{M}_{\odot }$$ yr^-1 for an assumed wind velocity of v_w = 1000 km s^-1). Similar to AT 2018cow, the detected X-ray emission is in excess compared to the extrapolated synchrotron spectrum and constitutes a different emission component, possibly powered by accretion onto a newly formed black hole or neutron star. These properties make AT 2020xnd a high-redshift analog to AT 2018cow, and establish AT 2020xnd as the fourth member of the class of optically luminous FBOTs with luminous multiwavelength counterparts.

• Research Organization: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS)
• Sponsoring Organization: Heising-Simons Foundation; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE Office of Science (SC)
• OSTI ID: 1983220
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 2 Vol. 926; ISSN 0004-637X
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English