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تسجيل مستخدم جديدRadio Observations of an Ordinary Outflow from the Tidal Disruption Event AT2019dsg
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We present detailed radio observations of the tidal disruption event (TDE) AT2019dsg, obtained with the Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA), and spanning $55-560$ days post-disruption. We find that the peak brightness of the radio emission increases until ~200 days and subsequently begins to decrease steadily. Using the standard equipartition analysis, including the effects of synchrotron cooling as determined by the joint VLA-ALMA spectral energy distributions, we find that the outflow powering the radio emission is in roughly free expansion with a velocity of $approx 0.07c$, while its kinetic energy increases by a factor of about 5 from 55 to 200 days and plateaus at $approx 5times 10^{48}$ erg thereafter. The ambient density traced by the outflow declines as $approx R^{-1.6}$ on a scale of $approx (1-4)times 10^{16}$ cm ($approx 6300-25000$ $R_s$), followed by a steeper decline to $approx 6times 10^{16}$ cm ($approx 37500$ $R_s$). Allowing for a collimated geometry, we find that to reach even mildly relativistic velocities ($Gamma=2$) the outflow requires an opening angle of $theta_japprox 2^circ$, which is narrow even by the standards of GRB jets; a truly relativistic outflow requires an unphysically narrow jet. The outflow velocity and kinetic energy in AT2019dsg are typical of previous non-relativistic TDEs, and comparable to those from Type Ib/c supernovae, raising doubts about the claimed association with a high-energy neutrino event.
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