The tidal disruption event AT2017eqx: spectroscopic evolution from hydrogen rich to poor suggests an atmosphere and outflow

Nicholl, M.; Blanchard, P. K.; Berger, E.; Gómez, Sebastián; Margutti, R.; Alexander, K. D.; Guillochon, James; Leja, Joel; Chornock, R.; Snios, Bradford; Auchettl, Katie; Bruce, Alastair; Challis, Peter; D’Orazio, Daniel J.; Drout, M. R.; Eftekhari, T.; Foley, R. J.; Graur, Or; Kilpatrick, C. D.; Lawrence, Andy; Piro, Anthony L.; Rojas-Bravo, C.; Ross, Nicholas P.; Short, P.; Smartt, S. J.; Smith, Kenneth; Stalder, B.

doi:10.1093/mnras/stz1837

Cited by 69 publications

(49 citation statements)

References 106 publications

(233 reference statements)

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“…We also plot the Xray light curve to highlight the X-ray to optical ratio, which is 10 −2.8 before peak. Since the X-rays appear to rise after the optical emission starts to fade, this ratio increases to ≈10 −2.0 − 10 −1.8 between 20-50 d after bolometric peak, and reaches ≈10 −1.4 beyond 50 d. (Gezari et al 2012;Arcavi et al 2014;Chornock et al 2014;Holoien et al 2014Holoien et al , 2016aBlagorodnova et al 2017;Leloudas et al 2019;Nicholl et al 2019b;van Velzen et al 2019;Gomez et al 2020) We plot the bolometric light curve compared to other wellobserved TDEs in Fig. 10.…”

Section: Bolometric Light Curvementioning

confidence: 99%

“…Arcavi et al 2014;Leloudas et al 2019). This prompted van to suggest three subclasses labelled TDE-H, TDE-He, and TDE-Bowen, though some TDEs defy a consistent classification by changing their apparent spectral type as they evolve (Nicholl et al 2019b).…”

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confidence: 99%

“…Inhibiting progress is the messy geometry of the debris. 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).…”

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confidence: 99%

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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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Section: Bolometric Light Curvementioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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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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“…The optical spectra of TDEs are usually dominated by very broad (FWHM 10 4 km s −1 ) H and/or He ii lines (e.g., Arcavi et al 2014). Usually, the relative strengths of H to He ii emission in an individual TDE are relatively constant, although there are counter examples: ASASSN-15oi had weak, transient H features (Holoien et al 2018), while AT 2017eqx transitioned from being H-dominated to being He ii-dominated (Nicholl et al 2019). Many TDEs also show optical emission lines attributable to N iii and O iii (Blagorodnova et al 2019;Leloudas et al 2019).…”

Section: Introductionmentioning

confidence: 99%

To TDE or not to TDE: the luminous transient ASASSN-18jd with TDE-like and AGN-like qualities

Neustadt

Holoien

Kochanek

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the discovery of ASASSN-18jd (AT 2018bcb), a luminous optical/UV/Xray transient located in the nucleus of the galaxy 2MASX J22434289-1659083 at z = 0.1192. Swift UVOT photometry shows the UV SED of the transient to be well modeled by a slowly shrinking blackbody with temperature T ∼ 2.5 × 10 4 K, a maximum observed luminosity of L max = 4.5 +0.6 −0.3 ×10 44 erg s −1 , and a total radiated energy of E = 9.6 +1.1 −0.6 × 10 51 erg. X-ray data from Swift XRT and XMM-Newton show a transient, variable X-ray flux with blackbody and power-law components. Optical spectra show strong, roughly constant broad Balmer emission as well as transient features attributable to He ii, N iii-v, O iii, and coronal Fe. While ASASSN-18jd shares similarities with Tidal Disruption Events (TDEs), it is also similar to the "rapid turn-on" events seen in quiescent galaxies and in faint Active Galactic Nuclei (AGNs).

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“…The Pantheon sample of Type Ia SNe is now the leading sample for cosmological constraints (Scolnic et al 2018a) and the Foundation Supernova Survey, a low redshift sample, has been recently published (Foley et al 2018). On the more exotic transient side, the Pan-STARRS project has made an impact in the discovery of tidal disruption events (Gezari et al 2012;Chornock et al 2014;Holoien et al 2019;Nicholl et al 2019) superluminous supernovae (SLSNe, Chomiuk et al 2011;McCrum et al 2015;Lunnan et al 2018), a population of 'fast-evolving' transients (Drout et al 2014), and outbursts of stars before core-collapse (Fraser et al 2013).…”

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confidence: 99%

PS15cey and PS17cke: prospective candidates from the Pan-STARRS Search for kilonovae

McBrien

Smartt

Huber

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Time domain astronomy was revolutionised with the discovery of the first kilonova, AT2017gfo, in August 2017 which was associated with the gravitational wave signal GW170817. Since this event, numerous wide-field surveys have been optimising search strategies to maximise their efficiency of detecting these fast and faint transients. With the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), we have been conducting a volume limited survey for intrinsically faint and fast fading events to a distance of D ≃ 200 Mpc. Two promising candidates have been identified from this archival search, with sparse data - PS15cey and PS17cke. Here we present more detailed analysis and discussion of their nature. We observe that PS15cey was a luminous, fast declining transient at 320 Mpc. Models of BH-NS mergers with a very stiff equation of state could possibly reproduce the luminosity and decline but the physical parameters are extreme. A more likely scenario is that this was an AT2018kzr-like merger event. PS17cke was a faint and fast declining event at 15 Mpc. We explore several explosion scenarios of this transient including models of it as a NS-NS and BH-NS merger, the outburst of a massive luminous star, and compare it against other known fast fading transients. Although there is uncertainty in the explosion scenario due to difficulty in measuring the explosion epoch, we find PS17cke to be a plausible kilonova candidate from the model comparisons.

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The tidal disruption event AT2017eqx: spectroscopic evolution from hydrogen rich to poor suggests an atmosphere and outflow

Cited by 69 publications

References 106 publications

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

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

To TDE or not to TDE: the luminous transient ASASSN-18jd with TDE-like and AGN-like qualities

PS15cey and PS17cke: prospective candidates from the Pan-STARRS Search for kilonovae

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