Generalized equipartition method from an arbitrary viewing angle

Abstract

The equipartition analysis yields estimates of the radius and energy of synchrotron self-absorbed radio sources. Here we generalize this method to relativistic off-axis viewed emitters. We find that the Lorentz factor $\Gamma$ and the viewing angle $\theta$ cannot be determined independently but become degenerate along a trajectory of minimal energy solutions. The solutions are divided into on-axis and off-axis branches with the former reproducing the classical analysis. A relativistic source viewed off-axis can be disguised as an apparent Newtonian one. Applying this method to radio observations of several tidal disruption events (TDEs), we find that the radio flare of AT 2018hyz which was observed a few years after the optical discovery could have been produced by a relativistic off-axis jet with kinetic energy of $\sim 10^{53}\mathrm{erg}$ that was launched around the time of discovery.

13 pages, 11 figures, accepted for publication in MNRAS

References in corpus (25)

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Cited by in corpus (6)

• Swift J1644+57 as an off-axis Jet
• Interaction of an outflow with surrounding gaseous clouds as the origin of the late-time radio flares in TDEs
• Two-component off-axis jet model for radio flares of tidal disruption events
• Detection of disk-jet co-precession in a tidal disruption event
• Searching for Radio Transients with Inverted Spectra in Epoch 1 of VLASS and VCSS, and Identification of a Sample of Candidate Relativistic Nuclear Transients
• AT2019ijn: a fast-rising, slow-decaying blue optical transient with exceptionally bright radio emission