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

D. 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. SandD. Svinkin, C. Ward, S. Yang, A. Baldeschi, I. V. Chilingarian, Y. Dong, C. Esquivia, W. Fong, C. Guidorzi, P. Lundqvist, D. Milisavljevic, K. Paterson, D. E. Reichart, B. Shappee, M. C. Stroh, S. Valenti, B. A. Zauderer, B. Zhang

Research output: Contribution to journalArticle

1 Scopus citations

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 × 1039 erg s-1) and radio (L ν ∼ 1029 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 Γβc ≥ 0.55c at ∼100 days. This is faster than the non-relativistic AT 2018cow (Γβc ∼ 0.1c) and closer to ZTF18abvkwla (Γβc ≥ 0.3c at 63 days). The inferred initial kinetic energy of CSS161010 (E k ⪆ 1051 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 dwarf galaxy with stellar mass M * ∼ 107 M o&dot; 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.

Original languageEnglish (US)
Article numberL23
JournalAstrophysical Journal Letters
Volume895
Issue number1
DOIs
StatePublished - May 20 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    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., ... Zhang, B. (2020). A Mildly Relativistic Outflow from the Energetic, Fast-rising Blue Optical Transient CSS161010 in a Dwarf Galaxy. Astrophysical Journal Letters, 895(1), [L23]. https://doi.org/10.3847/2041-8213/ab8cc7