Radio Properties of Tidal Disruption Events

Alexander, K. D.; Velzen, S. van; Horesh, A.; Zauderer, B. A.

doi:10.1007/s11214-020-00702-w

Cited by 160 publications

(154 citation statements)

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“…We can also compare the rate of radio-selected TDEs (CNSS 0019+00-like events) with that of optically-selected TDEs, ∼50 Gpc −3 yr −1 (van Velzen & Farrar 2014). The radio TDE rate therefore represents ∼20% of the rate of optically-selected TDEs, despite probing the same approximate volume (within z=0.1), though we note that this discrepancy is not unexpected given the uncertainty in the radio luminosity function of thermal TDEs 12 (Alexander et al 2020;Stone et al 2020). Finally, we note that, given our rate of radio TDEs, we expect to find tens of events like CNSS J0019+00 in all-sky radio surveys being executed with the VLA (VLASS; Lacy et al 2020) and ASKAP (Murphy et al 2013)-more numerous than the number of TDEs expected previously.…”

Section: Summary and Discussionmentioning

confidence: 71%

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

Anderson

Mooley

Hallinan

et al. 2020

ApJ

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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.

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Section: Summary and Discussionmentioning

confidence: 71%

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

Anderson

Mooley

Hallinan

et al. 2020

ApJ

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“…However, it is clear that sub-mJy radio cores can conceal both strong SF and an active, low-brightness SMBH (Padovani 2016), even in a flaring or dimming stage of accretion, such as in the case of a TDE, as observed in our target NGC 3690 (Arp 299, Mattila et al 2018). Therefore, by eventually disentangling SF and SMBH activity and assessing the origin of the radio emission at the centre of our galaxies, the next LeMMINGs papers will make use of the optical and X-ray data along with our radio observations to address the following astrophysical open issues: the disc-jet connection in LLAGN (Merloni et al 2003), the contribution from SF (stellar processes and XRBs) in the GHz band and possible core variability due to transient phenomena (Mundell et al 2009;Alexander et al 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Radio core variability on a time scale of a few years, episodic accretion onto the BH and nuclear inactivity expected within a typical duty cycle of 10 8 years could also account for their current none detection (e.g. Mundell et al 2009;Morganti 2017;Alexander et al 2020). Future e-MERLIN 5 GHz observations of the LeMMINGs targets with higher resolution and sensitivity will be able to possibly pinpoint the core with higher accuracy than L-band data.…”

Section: Undetected Galaxiesmentioning

confidence: 96%

LeMMINGs – II. The e-MERLIN legacy survey of nearby galaxies. The deepest radio view of the Palomar sample on parsec scale

Baldi

Williams

McHardy

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the second data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 177 nearby galaxies from the Palomar sample, observed with the e-MERLIN array, as part of the LeMMINGs (Legacy e-MERLIN Multi-band Imaging of Nearby Galaxy Sample) survey. Together with the 103 targets of the first LeMMINGs data release, this represents a complete sample of 280 local active (LINER and Seyfert) and inactive galaxies (H ii galaxies and Absorption Line Galaxies, ALG). This large program is the deepest radio survey of the local Universe, ≳ 1017.6 W Hz−1, regardless of the host and nuclear type: we detect radio emission ≳0.25 mJy beam−1 for 125/280 galaxies (44.6 per cent) with sizes of typically ≲100 pc. Of those 125, 106 targets show a core which coincides within 1.2 arcsec with the optical nucleus. Although we observed mostly cores, around one third of the detected galaxies features jetted morphologies. The detected radio core luminosities of the sample range between ∼1034 and 1040 erg s−1. LINERs and Seyferts are the most luminous sources, whereas H ii galaxies are the least. LINERs show FR I-like core-brightened radio structures while Seyferts reveal the highest fraction of symmetric morphologies. The majority of H ii galaxies have single radio core or complex extended structures, which probably conceal a nuclear starburst and/or a weak active nucleus (seven of them show clear jets). ALGs, which are typically found in evolved ellipticals, although the least numerous, exhibit on average the most luminous radio structures, similar to LINERs.

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“…Such flares are now regularly discovered, at a rate exceeding a few per year, by the various wide-field time-domain surveys (e.g. Gezari et al 2012;Arcavi et al 2014;Holoien et al 2014;van Velzen et al 2020).…”

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confidence: 99%

“…Colliding streams, inflowing and outflowing gas, and a viewing-angle dependence on both the broad-band (Dai et al 2018) and spectroscopic (Nicholl et al 2019b) properties all contribute to a messy knot that must be untangled. One important clue comes from radio observations: although only a small (but growing) sample of TDEs has been detected in the radio, in such cases we can measure the properties (energy, velocity, and density) of an outflow directly (see recent review by Alexander et al 2020). In some TDEs this emission is from a relativistic jet (Bloom et al 2011;Burrows et al 2011;Zauderer et al 2011;Cenko et al 2012;Mattila et al 2018), which does not appear to be a common feature of TDEs, but other radio TDEs have launched subrelativistic outflows (Alexander et al 2016(Alexander et al , 2017van Velzen et al 2016;Anderson et al 2019) A number of radio-quiet TDEs have exhibited indirect evidence for slower outflows in the form of blueshifted optical/UV emission and absorption lines (Blanchard et al 2017;Roth & Kasen 2018;Hung et al 2019), suggesting that outflows may be common.…”

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confidence: 99%

An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz

Nicholl

Wevers

Oates

et al. 2020

Monthly Notices of the Royal Astronomical Society

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At 66 Mpc, AT2019qiz is the closest optical tidal disruption event (TDE) to date, with a luminosity intermediate between the bulk of the population and the faint-and-fast event iPTF16fnl. Its proximity allowed a very early detection and triggering of multiwavelength and spectroscopic follow-up well before maximum light. The velocity dispersion of the host galaxy and fits to the TDE light curve indicate a black hole mass ≈106 M⊙, disrupting a star of ≈1 M⊙. By analysing our comprehensive UV, optical, and X-ray data, we show that the early optical emission is dominated by an outflow, with a luminosity evolution L ∝ t2, consistent with a photosphere expanding at constant velocity (≳2000 km s−1), and a line-forming region producing initially blueshifted H and He ii profiles with v = 3000–10 000 km s−1. The fastest optical ejecta approach the velocity inferred from radio detections (modelled in a forthcoming companion paper from K. D. Alexander et al.), thus the same outflow may be responsible for both the fast optical rise and the radio emission – the first time this connection has been observed in a TDE. The light-curve rise begins 29 ± 2 d before maximum light, peaking when the photosphere reaches the radius where optical photons can escape. The photosphere then undergoes a sudden transition, first cooling at constant radius then contracting at constant temperature. At the same time, the blueshifts disappear from the spectrum and Bowen fluorescence lines (N iii) become prominent, implying a source of far-UV photons, while the X-ray light curve peaks at ≈1041 erg s−1. Assuming that these X-rays are from prompt accretion, the size and mass of the outflow are consistent with the reprocessing layer needed to explain the large optical to X-ray ratio in this and other optical TDEs, possibly favouring accretion-powered over collision-powered outflow models.

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Radio Properties of Tidal Disruption Events

Cited by 160 publications

References 130 publications

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

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

LeMMINGs – II. The e-MERLIN legacy survey of nearby galaxies. The deepest radio view of the Palomar sample on parsec scale

An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz

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