The Long Term Evolution of ASASSN-14li

Brown, J. S.; Holoien, T. W. S.; Auchettl, Katie; Stanek, K. Z.; Kochanek, C. S.; Shappee, B. J.; Prieto, J. L.; Grupe, D.

doi:10.1093/mnras/stx033

Cited by 65 publications

(110 citation statements)

References 76 publications

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“…11). Also the optival/UV light curves of the TDFs in our sample are all consistent with a power-law decay rate; in all cases where monitoring observations cover more than one year of the light curve, an exponential decay rate can be ruled out Arcavi et al 2014;Gezari et al 2015;van Velzen et al 2016b;Brown et al 2016Brown et al , 2017. Note.…”

Section: Observed Tdfssupporting

confidence: 69%

On the Mass and Luminosity Functions of Tidal Disruption Flares: Rate Suppression due to Black Hole Event Horizons

Velzen

2018

ApJ

127

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The tidal disruption of a star by a massive black hole is expected to yield a luminous flare of thermal emission. About two dozen of these stellar tidal disruption flares (TDFs) may have been detected in optical transient surveys. However, explaining the observed properties of these events within the tidal disruption paradigm is not yet possible. This theoretical ambiguity has led some authors to suggest that optical TDFs are due to a different process, such as a nuclear supernova or accretion disk instabilities. Here we present a test of a fundamental prediction of the tidal disruption event scenario: a suppression of the flare rate due to the direct capture of stars by the black hole. Using a recently compiled sample of candidate TDFs with black hole mass measurements, plus a careful treatment of selection effects in this flux-limited sample, we confirm that the dearth of observed TDFs from high-mass black holes is statistically significant. All the TDF impostor models we consider fail to explain the observed mass function; the only scenario that fits the data is a suppression of the rate due to direct captures. We find that this suppression can explain the low volumetric rate of the luminous TDF candidate ASASSN-15lh, thus supporting the hypothesis that this flare belongs to the TDF family. Our work is the first to present the optical TDF luminosity function. A steep power law is required to explain the observed rest-frame g-band luminosity, dN/dL g ∝ L −2.5 g . The mean event rate of the flares in our sample is ≈ 1 × 10 −4 galaxy −1 yr −1 , consistent with the theoretically expected tidal disruption rate.

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Section: Observed Tdfssupporting

confidence: 69%

On the Mass and Luminosity Functions of Tidal Disruption Flares: Rate Suppression due to Black Hole Event Horizons

Velzen

2018

ApJ

127

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“…The fact that the object is still bright in the UV and X-rays years after the peak is also in line with what seen in other TDEs (e.g. Brown et al (2017);Jonker et al (2019)).…”

Section: Tidal Disruption Eventsupporting

confidence: 89%

Extreme variability in an active galactic nucleus: Gaia16aax

Cannizzaro

Fraser

Jonker

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the results of a multi-wavelength follow up campaign for the luminous nuclear transient Gaia16aax, which was first identified in January 2016. The transient is spatially consistent with the nucleus of an active galaxy at z=0.25, hosting a black hole of mass ∼ 6 × 10 8 M . The nucleus brightened by more than 1 magnitude in the Gaia G-band over a timescale of less than one year, before fading back to its preoutburst state over the following three years. The optical spectra of the source show broad Balmer lines similar to the ones present in a pre-outburst spectrum. During the outburst, the Hα and Hβ emission lines develop a secondary peak. We also report on the discovery of two transients with similar light curve evolution and spectra: Gaia16aka and Gaia16ajq. We consider possible scenarios to explain the observed outbursts. We exclude that the transient event could be caused by a microlensing event, variable dust absorption or a tidal encounter between a neutron star and a stellar mass black hole in the accretion disk. We consider variability in the accretion flow in the inner part of the disk, or a tidal disruption event of a star ≥ 1M by a rapidly spinning supermassive black hole as the most plausible scenarios. We note that the similarity between the light curves of the three Gaia transients may be a function of the Gaia alerts selection criteria.

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“…In order to derive upper limits on the X-ray flux, we adopt a characteristic Xray temperature of 5 × 10 5 K, as we found for ASASSN-14li (Brown et al 2016b). We correct for Galactic absorption assuming a column density of 5.6 × 10 20 cm −2 (Kalberla et al 2005).…”

Section: Photometric Analysismentioning

confidence: 99%

The ultraviolet spectroscopic evolution of the low-luminosity tidal disruption event iPTF16fnl

Brown

Kochanek

Holoien

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the ultraviolet (UV) spectroscopic evolution of a tidal disruption event (TDE) for the first time. After the discovery of the nearby TDE iPTF16fnl, we obtained a series of observations with the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST). The dominant emission features closely resemble those seen in the UV spectra of the TDE ASASSN-14li and are also similar to those of N-rich quasars. However, there is significant evolution in the shape and central wavelength of the line profiles over the course of our observations, such that at early times the lines are broad and redshifted, while at later times the lines are significantly narrower and peak near the wavelengths of their corresponding atomic transitions. Like ASASSN-14li, but unlike N-rich quasars, iPTF16fnl shows neither Mg ii λ2798Å nor C iii] λ1909Å emission features. We also present optical photometry and spectroscopy, which suggest that the complex He ii profiles observed in the optical spectra of many TDEs are in part due to the presence of N iii and C iii Wolf-Rayet features, which can potentially serve as probes of the far-UV when space-based observations are not possible. Finally, we use Swift XRT and UVOT observations to place strong limits on the X-ray emission and determine the characteristic temperature, radius, and luminosity of the emitting material. We find that iPTF16fnl is subluminous and evolves more rapidly than other optically discovered TDEs.

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The Long Term Evolution of ASASSN-14li

Cited by 65 publications

References 76 publications

On the Mass and Luminosity Functions of Tidal Disruption Flares: Rate Suppression due to Black Hole Event Horizons

On the Mass and Luminosity Functions of Tidal Disruption Flares: Rate Suppression due to Black Hole Event Horizons

Extreme variability in an active galactic nucleus: Gaia16aax

The ultraviolet spectroscopic evolution of the low-luminosity tidal disruption event iPTF16fnl

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