The influence of circumnuclear environment on the radio emission from TDE jets

Abstract

Dozens of stellar tidal disruption events (TDEs) have been identified at optical, UV and X-ray wavelengths. A small fraction of these, most notably Swift J1644+57, produce radio synchrotron emission, consistent with a powerful, relativistic jet shocking the surrounding circumnuclear gas. The dearth of similar non-thermal radio emission in the majority of TDEs may imply that powerful jet formation is intrinsically rare, or that the conditions in galactic nuclei are typically unfavorable for producing a detectable signal. Here we explore the latter possibility by constraining the radial profile of the gas density encountered by a TDE jet using a one-dimensional model for the circumnuclear medium which includes mass and energy input from a stellar population. Near the jet Sedov radius of 10 18 cm, we find gas densities in the range of n 18 ∼ 0.1−1000 cm −3 across a wide range of plausible star formation histories. Using one-and two-dimensional relativistic hydrodynamical simulations, we calculate the synchrotron radio light curves of TDE jets (as viewed both on and off-axis) across the allowed range of density profiles. We find that bright radio emission would be produced across the plausible range of nuclear gas densities by jets as powerful as Swift J1644+57, and we quantify the relationship between the radio luminosity and jet energy. We use existing radio detections and upper limits to constrain the energy distribution of TDE jets. Radio follow up observations several months to several years after the TDE candidate will strongly constrain the energetics of any relativistic flow.

Long Fading Mid-Infrared Emission in Transient Coronal Line Emitters: Dust Echo of a Tidal Disruption Flare

“…Assuming a dust to gas ratio of 0.01, the amount of gas is 14, 76, 29, and 18 M e for J0748+4712, J0952+2143, J1342+0530, and J1350+2916, respectively. This is consistent with the recent theoretical works on the circumnuclear medium in quiescent galaxies (Generozov et al 2015(Generozov et al , 2016. Therefore, the dust and gas in the four TDEs with ECLs is about 1000-5000 times richer than the one in ASASSN-14li (Jiang et al 2016).…”

iPTF16fnl: A Faint and Fast Tidal Disruption Event in an E+A Galaxy

“…We compare our limits in 6 and 15 GHz with the analytical light curves for on-axis TDE radio emission from Generozov et al (2017). Figure 4 shows that our .…”

“…The spectroscopic data are made public via WISeREP Upper limits for our 6 GHz (small triangle) and 15 GHz (big triangles) observations. The lines show analytic light curves for different TDE on-axis jet energies (color-coded) from Generozov et al (2017). Solid lines represent the light curves for 15 GHz and dashed lines represent those for 6 GHz.…”

High-energy cosmic ray nuclei from tidal disruption events: Origin, survival, and implications

“…The CNM gas density in the galaxy nuclear region is still unclear. It can originate from the stellar winds, and their profile depends on the detailed distribution of stars and star formation history in the galaxy nuclear region [84,85]. We assume that the CNM density is constant in our analysis, which is reasonable for galaxy cores [84].…”