Caltech–NRAO Stripe 82 Survey (CNSS). III. The First Radio-discovered Tidal Disruption Event, CNSS J0019+00

Abstract

We present the discovery of a nuclear transient with the Caltech-NRAO Stripe 82 Survey (CNSS), a dedicated radio transient survey carried out with the Karl G.Jansky Very Large Array (VLA). This transient, CNSS J001947.3+003527, exhibited a turn-on over a timescale of 1 yr, increasing in flux density at 3 GHz from <0.14 mJy in 2014 February to 4.4±0.1 mJy in 2015 March, reaching a peak luminosity of-5 10 erg s Hz 28 1 1 around 2015 October. The association of CNSS J0019+00 with the nucleus (Gaia and our very-long baseline interferometry positions are consistent to within 1 pc) of a nearby S0 Seyfert galaxy at 77 Mpc, together with the radio spectral evolution, implies that this transient is most likely a tidal disruption event (TDE). Our equipartition analysis indicates the presence of a ∼15,000 km s −1 outflow, having energy ∼10 49 erg. We derive the radial density profile for the circumnuclear material in the host galaxy to be proportional to R −2.5. All of these properties suggest resemblance with radio-detected thermal TDEs like ASASSN-14li and XMMSL1 J0740-85. No significant X-ray or optical emission is detected from CNSS J0019+00, although this may simply be due to the thermal emission being weak during our late-time follow-up observations. From the CNSS survey we have obtained the first unbiased measurement of the rate of radio TDEs, R(>500μJy) of about 2×10 −3 deg −2 , or equivalently a volumetric rate of about 10 Gpc −3 yr −1. This rate implies that all-sky radio surveys such as the VLA Sky Survey and those planned with ASKAP, will find many tens of radio TDEs over the next few years.

Quasars That Have Transitioned from Radio-quiet to Radio-loud on Decadal Timescales Revealed by VLASS and FIRST

“…Tidal disruption events (TDEs; e.g., Komossa 2015, and references therein) occur when a star passes within the tidal radius of an SMBH and is ripped apart and partially accreted onto the SMBH. This leads to a multiwavelength flare, which in some cases includes the production of radio continuum emission associated with nonthermal jets or thermal outflows (van Velzen et al 2011(van Velzen et al , 2016Anderson et al 2020). The most radio luminous known TDE, Swift J1644+57, peaked at ∼10 32 ergs −1 Hz −1 (Eftekhari et al 2018), which is roughly in line with the radio luminosities of our sources.…”

Tidal Disruption Events and High-energy Neutrinos

“…ZTF alone is now finding TDEs at a rate > 1 per month, though ZTF is of course not operating alone. TDEs are also being discovered by other optical surveys including PanSTARRS [12], ASAS-SN [13], GAIA [14] and ATLAS [15], X-ray surveys such as eROSITA [16], as well as radio surveys such as CNSS [17] and FIRST/VLASS [18]. As can be seen in Figure 2, the sample of confirmed and probable TDEs has vastly increased to more than 70, a doubling since the 36th ICRC.…”

Tidal Disruption Events and High-Energy Neutrinos

“…ZTF alone is now finding TDEs at a rate > 1 per month, though ZTF is of course not operating alone. TDEs are also being discovered by other optical surveys including PanSTARRS [12], ASAS-SN [13], GAIA [14] and ATLAS [15], X-ray surveys such as eROSITA [16], as well as radio surveys such as CNSS [17] and FIRST/VLASS [18]. As can be seen in Figure 2, the sample of confirmed and probable TDEs has vastly increased to more than 70, a doubling since the 36th ICRC.…”