Swift spectra of AT2018cow: a white dwarf tidal disruption event?

Kuin, N. P. M.; Wu, Kinwah; Oates, S. R.; Lien, A. Y.; Emery, S. W. K.; Kennea, J. A.; Pasquale, M. de; Han, Qin; Brown, P. J.; Tohuvavohu, A.; Breeveld, A. A.; Burrows, D. N.; Cenko, S. B.; Campana, S.; Levan, A. J.; Markwardt, C. B.; Osborne, J. P.; Page, M. J.; Page, K. L.; Sbarufatti, B.; Siegel, M. H.; Troja, E.

doi:10.1093/mnras/stz053

Cited by 87 publications

(115 citation statements)

References 71 publications

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“…AT2018cow: A rapidly rising and luminous transient was discovered in the optical by Prentice et al (2018) and also detected in the X-ray, radio, and submillimeter (Rivera Sandoval et al 2018;Kuin et al 2019;Margutti et al 2018). A TDE involving a He-star and an IMBH was suggested by Ho et al (2019).…”

Section: Multi-wavelength Candidatesmentioning

confidence: 96%

Tidal Disruptions of White Dwarfs: Theoretical Models and Observational Prospects

et al. 2020

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White dwarf stars that enter the tidal radius of black holes with masses < ∼ 10 5 M are doomed to be ripped apart by tidal forces. Black holes in this mass range between stellar black holes and supermassive black holes have not been conclusively identified so the detection of a tidal disruption of a white dwarf would provide clear evidence for the existence of intermediatemass black holes. In this review, we present a theoretical and observational overview of the transient events that result from the tidal disruptions of white dwarfs by intermediate-mass black holes. This includes discussion of the latest simulations and predicted properties, the results of observational searches, as well as a summary of the potential for gravitational wave emission to be detected with upcoming missions.

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Section: Multi-wavelength Candidatesmentioning

confidence: 96%

Tidal Disruptions of White Dwarfs: Theoretical Models and Observational Prospects

et al. 2020

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“…In particular, the relativistic beaming induced by the marginally-relativistic velocity, and the prediction for the time over which the shock speed declines to sub-relativistic speeds, would yield correspondingly different break timescales for the lightcurve of the event and peaks in the synchrotron spectrum (e.g., Sari et al 1998;De Colle et al 2012). The event AT2018cow (Prentice et al 2018;Rivera Sandoval et al 2018;Ho et al 2019;Kuin et al 2019;Margutti et al 2019;Perley et al 2019), tentatively an extreme example of the class of fast-rising transients (Drout et al 2014), also provided evidence of a moderately relativistic outflow with speed ∼ 0.1c; the model presented here could be combined with current multiwavelength data to further constrain properties of the progenitor and surrounding medium. This work was supported by NASA through the Einstein Fellowship Program, Grant PF6-170170.…”

Section: Discussionmentioning

confidence: 99%

Energy-conserving Relativistic Corrections to Strong-shock Propagation

Coughlin

2019

ApJ

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Astrophysical explosions are accompanied by the propagation of a shock wave through an ambient medium. Depending on the mass and energy involved in the explosion, the shock velocity V can be non-relativistic (V ≪ c, where c is the speed of light), ultra-relativistic (V ≃ c), or moderately relativistic (V ∼ f ew × 0.1c). While self-similar, energy-conserving solutions to the fluid equations that describe the shock propagation are known in the non-relativistic (the Sedov-Taylor blastwave) and ultra-relativistic (the Blandford-McKee blastwave) regimes, the finite speed of light violates scale invariance and self-similarity when the flow is only mildly relativistic. By treating relativistic terms as perturbations to the fluid equations, here we derive the O(V 2 /c 2 ), energy-conserving corrections to the non-relativistic, Sedov-Taylor solution for the propagation of a strong shock. We show that relativistic terms modify the post-shock fluid velocity, density, pressure, and the shock speed itself, the latter being constrained by global energy conservation. We derive these corrections for a range of post-shock adiabatic indices γ (which we set as a fixed number for the post-shock gas) and ambient power-law indices n, where the density of the ambient medium ρ a into which the shock advances declines with spherical radius r as ρ a ∝ r −n . For Sedov-Taylor blastwaves that terminate in a contact discontinuity with diverging density, we find that there is no relativistic correction to the Sedov-Taylor solution that simultaneously satisfies the fluid equations and conserves energy. These solutions have implications for relativistic supernovae, the transition from ultra-to sub-relativistic velocities in gamma-ray bursts, and other high-energy phenomena.All of these explosion scenarios involve the formation and expansion of a shock wave into its surroundings, and this shock leaves in its wake a "sea" of post-shock fluid (as, of course, do explosion scenarios not initiated by the collapse of a massive star, such as compact object mergers; e.g., Li & Paczyński 1998;Levinson et al. 2002;Nakar & Piran 2011;Abbott et al. 2017). One of the most useful techniques for describing the spatial and temporal evolution of the post-shock gas and of the shock itself is self-similarity. This mathematical technique exploits the scale invariance of the fluid equations and, in the absence of any temporal or spatial scales of the ambient medium, the necessary scale invariance of the solutions to those equations (e.g., Ostriker & McKee 1988).Among the best-known examples of a self-similar solution to the fluid equations is the Sedov-Taylor (ST) blastwave (Sedov 1959;Taylor 1950). The ST blastwave describes the propagation of an energy-conserving, strong (Mach number much greater than one) shock into an ambient medium that possesses a power-law density profile. The conservation of energy implies that there is a unique shock speed V that can be directly related to the initial energy of the explosion, the impulsive injection of which initiated the e...

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“…AT 2018cow is the first FLBT observed in the local universe at z = 0.0139 (Prentice et al 2018;Kuin et al 2019;Perley et al 2019), which enabled multiwavelength follow-up observations. The transient was very bright L cow ∼ 10 10 L and rapid, with timescales of rising and declining are respectively t rise,1/2 ∼ 2.5 days and t decline,1/2 ∼ 3 days.…”

Section: Introductionmentioning

confidence: 93%

Fast Luminous Blue Transients in the Reionization Era and Beyond

Terasaki

Tsuna²,

Shigeyama³

2020

ApJL

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To determine the epoch of reionization precisely and to reveal the property of inhomogeneous reionization are some of the most important topics of modern cosmology. Existing methods to investigate reionization which use cosmic microwave background, Lyα emitters, quasars, or gamma ray bursts, have difficulties in terms of accuracy or event rate. We propose that recently discovered fast luminous blue transients (FLBTs) have potential as a novel probe of reionization. We study the detectability of FLBTs at the epoch of reionization with upcoming WFIRST Wide-Field Instruments (WFI), using a star formation rate derived from galaxy observations and an event rate of FLBTs proportional to the star formation rate. We find that if FLBTs occur at a rate of 1% of the core-collapse supernova rate, 2 (0.3) FLBTs per year per deg 2 at z > 6 (z > 8) can be detected by a survey with a limiting magnitude of 26.5 mag in the near-infrared band and a cadence of 10 days. We conclude that the WFIRST supernova deep survey can detect ∼ 20 FLBTs at the epoch of reionization in the near future.

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Swift spectra of AT2018cow: a white dwarf tidal disruption event?

Cited by 87 publications

References 71 publications

Tidal Disruptions of White Dwarfs: Theoretical Models and Observational Prospects

Tidal Disruptions of White Dwarfs: Theoretical Models and Observational Prospects

Energy-conserving Relativistic Corrections to Strong-shock Propagation

Fast Luminous Blue Transients in the Reionization Era and Beyond

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