ASASSN-15oi: a rapidly evolving, luminous tidal disruption event at 216 Mpc

Holoien, T. W. S.; Kochanek, C. S.; Prieto, J. L.; Grupe, D.; Chen, Ping; Godoy-Rivera, D.; Stanek, K. Z.; Shappee, B. J.; Dong, Subo; Brown, J. S.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Carlson, Erika K.; Falco, E.; Johnston, Evelyn J.; Madore, Barry F.; Pojmański, G.; Seibert, Mark

doi:10.1093/mnras/stw2272

Cited by 165 publications

(118 citation statements)

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“…While this limit is significantly fainter than the luminous X-ray emission observed from ASASSN-14li (Holoien et al 2016b;van Velzen et al 2016a), it is comparable to the much fainter emission observed from ASASSN-15oi (L X = 4.8 × 10 41 erg s −1 ; Holoien et al 2016a). Furthermore,it is several orders of magnitude above the faint X-ray emission observed at the location of iPTF16fnl (L X = 2.4 × 10 39 erg s −1 ; Blagorodnova et al 2017).…”

Section: Swift Uvot and Xrt Photometrymentioning

confidence: 48%

“…We then compare its properties with 11 TDE candidates discovered in UV and optical sky surveys with well-sampled optical light curves: D1-9 and D3-13 from GALEX+CFHTLS (Gezari et al 2008), TDE1 and TDE2 from SDSS (van Velzen et al 2011), PTF09ge from PTF (Arcavi et al 2014), PS1-10jh (Gezari et al 2012), and PS1-11af (Chornock et al 2014) from GALEX+Pan-STARRS1, ASASSN-14ae (Holoien et al 2014), ASASSN-14li (Holoien et al 2016b), and ASASSN-15oi (Holoien et al 2016a) from ASASSN, and iPTF16fnl (Blagorodnova et al 2017). The luminosities, temperatures, and radii of the three ASASSN candidate TDEs (ASASSN-14ae, ASASSN-14li, ASASSN-15oi) are provided by T. Holoien via private communication.…”

Section: Discussionmentioning

confidence: 99%

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Revisiting Optical Tidal Disruption Events with iPTF16axa

Hung

Gezari

Blagorodnova

et al. 2017

ApJ

177

174

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We report the discovery by the intermediate Palomar Transient Factory (iPTF) of a candidate tidal disruption event (TDE) iPTF16axa at z=0.108 and present its broadband photometric and spectroscopic evolution from threemonths of follow-up observations with ground-based telescopes and Swift. The light curve is well fitted with a t −5/3 decay, and we constrain the rise time to peak to be <49 rest-frame days after disruption, which is roughly consistent with the fallback timescale expected for the ∼5×106 M e black hole inferred from the stellar velocity dispersion of the host galaxy. The UV and optical spectral energy distribution is well described by a constant blackbody temperature of T∼3×10 4 K over the monitoring period, with an observed peak luminosity of 1.1×10 44 erg s −1. The optical spectra are characterized by a strong blue continuum and broad He II and Hα lines, which are characteristic of TDEs. We compare the photometric and spectroscopic signatures of iPTF16axa with 11 TDE candidates in the literature with well-sampled optical light curves. Based on a single-temperature fit to the optical and near-UV photometry, most of these TDE candidates have peak luminosities confined between log(L [erg s 4 K during their power-law declines, implying blackbody radii on the order of 10 times the tidal disruption radius, that decrease monotonically with time. For TDE candidates with hydrogen and helium emission, the high helium-to-hydrogen ratios suggest that the emission arises from high-density gas, where nebular arguments break down. We find no correlation between the peak luminosity and the black hole mass, contrary to the expectations for TDEs to have M M BH 1 2 µ -.

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Section: Swift Uvot and Xrt Photometrymentioning

confidence: 48%

Section: Discussionmentioning

confidence: 99%

Revisiting Optical Tidal Disruption Events with iPTF16axa

Hung

Gezari

Blagorodnova

et al. 2017

ApJ

177

174

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“…(3) The light curve of iPTF 16bco shows a complex shape uncharacteristic of a TDE, with a month-long plateau, followed by a 2-week rise to another plateau. (4) The broad Balmer lines in iPTF 16bco are narrower and stronger than have been observed in TDEs, and iPTF 16bco does not have strong, broad He II l4686, which is characteristic of TDE spectra (Gezari et al 2012;Arcavi et al 2014;Holoien et al 2014Holoien et al , 2016aHoloien et al , 2016b. (5) Finally, the broad-line emission and X-ray continuum in iPTF 16bco are consistent with radio-quiet quasars in the "Eigenvector 1" parameter space: the FWHM velocity width of the broad Hβ line versus the ratio of the equivalent widths of the Fe II λ4570 complex to broad Hβ strength (R Fe II ) (Sulentic et al 2000) favors a change inṀ acc of a preexisting accretion disk, instead of a newly formed debris disk from a TDE.…”

Section: Tidal Disruption Event (Tde)mentioning

confidence: 99%

“…In fact, the rapid rise and power-law decline of its light curve were interpreted as a signature of a TDE (Merloni et al 2015). However, the light curves of iPTF 16bco and the other changing-look quasars with archival photometry have large fluctuations that are inconsistent with the smooth, power-law decline observed in the optical light curves of known TDEs (e.g., Gezari et al 2008;van Velzen et al 2011;Gezari et al 2012;Arcavi et al 2014;Holoien et al 2014Holoien et al , 2016aHoloien et al , 2016b. The erratic intraburst behavior in the twostate (hot and cold) α instability models of Siemiginowska et al (1996) could be promising.…”

Section: Accretion Disk Instabilitiesmentioning

confidence: 99%

iPTF Discovery of the Rapid “Turn-on” of a Luminous Quasar

Gezari

Hung

Cenko

et al. 2017

ApJ

137

175

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We present a radio-quiet quasar at z=0.237 discovered "turning on" by the intermediate Palomar Transient Factory (iPTF). The transient, iPTF 16bco, was detected by iPTF in the nucleus of a galaxy with an archival Sloan Digital Sky Survey spectrum with weak narrow-line emission characteristic of a low-ionization nuclear emissionline region (LINER). Our follow-up spectra show the dramatic appearance of broad Balmer lines and a power-law continuum characteristic of a luminous ( » L 10 bol 45 erg s −1 ) type 1 quasar 12 yr later. Our photometric monitoring with PTF from 2009-2012 and serendipitous X-ray observations from the XMM-Newton Slew Survey in 2011 and 2015 constrain the change of state to have occurred less than 500 days before the iPTF detection. An enhanced broad Hα/[O III] λ5007 line ratio in the type 1 state relative to other changing-look quasars also is suggestive of the most rapid change of state yet observed in a quasar. We argue that the >10 increase in Eddington ratio inferred from the brightening in UV and X-ray continuum flux is more likely due to an intrinsic change in the accretion rate of a preexisting accretion disk than an external mechanism such as variable obscuration, microlensing, or the tidal disruption of a star. However, further monitoring will be helpful in better constraining the mechanism driving this change of state. The rapid "turn-on" of the quasar is much shorter than the viscous infall timescale of an accretion disk and requires a disk instability that can develop around a  M 10 8 black hole on timescales less than 1 yr.

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“…(Piran et al 2015 (P15); Roth et al 2016;Dai et al 2015;etc.). In some of the best-studied events, the optical/UV blackbody radius is much larger than the tidal radius, and the temperature remains roughly constant over much of the evolution (e.g., Chornock et al 2014;Holoien et al 2016b). Because TDFs are basically accreting supermassive black holes, the natural inclination is to expect the same mechanisms operating in AGN, namely, X-ray reprocessing, thermal emission from the inner radii of the accretion disk, etc., to also operate in TDFs.…”

Section: Introductionmentioning

confidence: 99%

Optical/UV-to-X-Ray Echoes from the Tidal Disruption Flare ASASSN-14li

Pasham

Cenko

Sądowski

et al. 2017

ApJL

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We carried out the first multi-wavelength (optical/UV and X-ray) photometric reverberation mapping of a tidal disruption flare (TDF) ASASSN-14li. We find that its X-ray variations are correlated with and lag the optical/UV fluctuations by 32±4 days. Based on the direction and the magnitude of the X-ray time lag, we rule out X-ray reprocessing and direct emission from a standard circular thin disk as the dominant source of its optical/UV emission. The lag magnitude also rules out an AGN disk-driven instability as the origin of ASASSN-14li and thus strongly supports the tidal disruption picture for this event and similar objects. We suggest that the majority of the optical/UV emission likely originates from debris stream self-interactions. Perturbations at the self-interaction sites produce optical/UV variability and travel down to the black hole where they modulate the X-rays. The time lag between the optical/UV and the X-rays variations thus correspond to the time taken by these fluctuations to travel from the self-interaction site to close to the black hole. We further discuss these time lags within the context of the three variants of the self-interaction model. High-cadence monitoring observations of future TDFs will be sensitive enough to detect these echoes and would allow us to establish the origin of optical/UV emission in TDFs in general.

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ASASSN-15oi: a rapidly evolving, luminous tidal disruption event at 216 Mpc

Cited by 165 publications

References 96 publications

Revisiting Optical Tidal Disruption Events with iPTF16axa

Revisiting Optical Tidal Disruption Events with iPTF16axa

iPTF Discovery of the Rapid “Turn-on” of a Luminous Quasar

Optical/UV-to-X-Ray Echoes from the Tidal Disruption Flare ASASSN-14li

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