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