Caltech-NRAO Stripe 82 Survey (CNSS). III: The First Radio-discovered Tidal Disruption Event, CNSS J0019+00. (arXiv:1910.11912v2 [astro-ph.HE] UPDATED)

Caltech-NRAO Stripe 82 Survey (CNSS). III: The First Radio-discovered Tidal Disruption Event, CNSS J0019+00. (arXiv:1910.11912v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Anderson_M/0/1/0/all/0/1">M. M. Anderson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mooley_K/0/1/0/all/0/1">K. P. Mooley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hallinan_G/0/1/0/all/0/1">G. Hallinan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dong_D/0/1/0/all/0/1">D. Dong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Phinney_E/0/1/0/all/0/1">E. S. Phinney</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Horesh_A/0/1/0/all/0/1">A. Horesh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bourke_S/0/1/0/all/0/1">S. Bourke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cenko_S/0/1/0/all/0/1">S. B. Cenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frail_D/0/1/0/all/0/1">D. Frail</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kulkarni_S/0/1/0/all/0/1">S. R. Kulkarni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Myers_S/0/1/0/all/0/1">S. Myers</a>

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 $lesssim$1 yr, increasing in flux
density at 3 GHz from $<0.14$ mJy in 2014 February to $4.4pm0.1$ mJy in 2015
March, reaching a peak luminosity of $5times10^{28} text{erg s}^{-1}
text{Hz}^{-1}$ around 2015 October. The association of CNSS J0019+00 with the
nucleus (Gaia and our VLBI 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 $sim$15,000 km s$^{-1}$
outflow, having energy $sim$10$^{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, $R(>500 mu{rm Jy})$ of about
$2times10^{-3}$ 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.

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 $lesssim$1 yr, increasing in flux
density at 3 GHz from $<0.14$ mJy in 2014 February to $4.4pm0.1$ mJy in 2015
March, reaching a peak luminosity of $5times10^{28} text{erg s}^{-1}
text{Hz}^{-1}$ around 2015 October. The association of CNSS J0019+00 with the
nucleus (Gaia and our VLBI 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 $sim$15,000 km s$^{-1}$
outflow, having energy $sim$10$^{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, $R(>500 mu{rm Jy})$ of about
$2times10^{-3}$ 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.

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