Synchrotron Afterglow Model for AT 2022cmc: Jetted Tidal Disruption Event or Engine-Powered Supernova?

Abstract

AT 2022cmc is a luminous optical transient ($\nu L_{\nu }\gtrsim 10^{45}$ erg s${}^{-1}$) accompanied by decaying non-thermal X-rays (peak duration $t_{\mathrm{X}}\lesssim$ days and isotropic energy $E_{\mathrm{X},\mathrm{iso}}\gtrsim 10^{53}$ erg) and a long-lived radio/mm synchrotron afterglow, which has been interpreted as a jetted tidal disruption event (TDE). Both an equipartition analysis and a detailed afterglow model reveals the radio/mm emitting plasma to be expanding mildly relativistically (Lorentz factor $\Gamma \gtrsim few$) with an opening angle ${\theta }_{\mathrm{j}}\simeq 0.1$ and roughly fixed energy $E_{\mathrm{j},\mathrm{iso}}\gtrsim few\times 10^{53}$ erg into an external medium of density profile $n\propto R^{-k}$ with $k\simeq 1.5-2$, broadly similar to that of the first jetted TDE candidate Swift J1644+57 and consistent with Bondi accretion at a rate $\sim 10^{-3}{\dot{M}}_{\mathrm{Edd}}$ onto a $10^6{M}_{\odot }$ black hole before the outburst. The rapidly decaying optical emission over the first days is consistent with fast-cooling synchrotron radiation from the same forward shock as the radio/mm emission, while the bluer slowly decaying phase to follow likely represents a separate thermal emission component. Emission from the reverse shock may have peaked during the first days, but whose non-detection in the optical band places an upper bound ${\Gamma }_{\mathrm{j}}\lesssim 100$ on the Lorentz factor of the unshocked jet. Although a TDE origin for AT 2022cmc is indeed supported by some observations, the vast difference between the short-lived jet activity phase $t_{\mathrm{X}}\lesssim$ days relative to the months-long thermal optical emission, also challenges this scenario. A stellar core-collapse event giving birth to a magnetar or black hole engine of peak duration $\sim 1$ day offers an alternative model also consistent with the circumburst environment, if interpreted as a massive-star wind.

11 pages, 9 figures, 2 tables, accepted for publication in MNRAS

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Cited by in corpus (6)

• Swift J1644+57 as an off-axis Jet
• Two-component off-axis jet model for radio flares of tidal disruption events
• Structured Jet Model for Multiwavelength Observations of the Jetted Tidal Disruption Event AT 2022cmc
• Revisiting X-ray Afterglows of Jetted Tidal Disruption Events with the External Reverse Shock
• Numerical Modeling of Relativistic Effects in Synchrotron-Emitting Shocks
• AT2024lhc and AT2024kmq in the landscape of featureless tidal disruption events