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. Drout; D. Frederiks; C. Frohmaier; K. 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; D. Milisavljevic; K. Paterson; D. E. Reichart; B. Shappee; M. C. Stroh; S. Valenti; A. Zauderer; B. Zhang

doi:10.3847/2041-8213/ab8cc7

paper

A mildly relativistic outflow from the energetic, fast-rising blue optical transient CSS161010 in a dwarf galaxy

arXiv:2003.10503 · doi:10.3847/2041-8213/ab8cc7

Abstract

We present X-ray and radio observations of the Fast Blue Optical Transient (FBOT) CRTS-CSS161010 J045834-081803 (CSS161010 hereafter) at t=69-531 days. CSS161010 shows luminous X-ray ( $L_{x} \sim 5 \times 1 0^{39} erg s^{- 1}$ ) and radio ( $L_{ν} \sim 1 0^{29} erg s^{- 1} H z^{- 1}$ ) 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 blastwave. CSS161010 launched a mildly relativistic outflow with velocity $Γ β c \geq 0.55 c$ at ~100 days. This is faster than the non-relativistic AT2018cow ( $Γ β c \sim 0.1 c$ ) and closer to ZTF18abvkwla ( $Γ β c \geq 0.3 c$ at 63 days). The inferred initial kinetic energy of CSS161010 ( $E_{k} ≳ 1 0^{51}$ erg) is comparable to that of long Gamma Ray Bursts (GRBs), but the ejecta mass that is coupled to the mildly relativistic outflow is significantly larger ( $\sim 0.01 - 0.1 M_{⊙}$ ). This is consistent with the lack of observed gamma-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 $M_{*} \sim 1 0^{7} M_{⊙}$ and specific star formation rate $s S F R \sim 0.3 Gy r^{- 1}$ . 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.

arXiv commentAccepted to ApJL

A mildly relativistic outflow from the energetic, fast-rising blue optical transient CSS161010 in a dwarf galaxy

Abstract

References in corpus (111)

Cited by in corpus (80)