Tidal Disruptions of Main-sequence Stars of Varying Mass and Age: Inferences from the Composition of the Fallback Material

Gallegos-Garcia, Monica; Law-Smith, Jamie A. P.; Ramírez-Ruiz, E.

doi:10.3847/1538-4357/aab5b8

Cited by 33 publications

(35 citation statements)

References 51 publications

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“…Additionally, mixing could be studied within the material stripped from the star. As suggested by Gallegos-Garcia et al (2018), compositional changes resulting from the fallback gas could be reflected in the TDE light curve, as well as the spectra. These features could be used to constrain the properties of the disrupted star.…”

Section: Discussionmentioning

confidence: 86%

Hydrodynamical moving-mesh simulations of the tidal disruption of stars by supermassive black holes

Goicovic

Springel

Ohlmann

et al. 2019

Monthly Notices of the Royal Astronomical Society

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When a star approaches a black hole closely, it may be pulled apart by gravitational forces in a tidal disruption event (TDE). The flares produced by TDEs are unique tracers of otherwise quiescent supermassive black holes (SMBHs) located at the centre of most galaxies. In particular, the appearance of such flares and the subsequent decay of the light curve are both sensitive to whether the star is partially or totally destroyed by the tidal field. However, the physics of the disruption and the fall-back of the debris are still poorly understood. We are here modelling the hydrodynamical evolution of realistic stars as they approach a SMBH on parabolic orbits, using for the first time the moving-mesh code AREPO, which is particularly well adapted to the problem through its combination of quasi-Lagrangian behaviour, low advection errors, and high accuracy typical of mesh-based techniques. We examine a suite of simulations with different impact parameters, allowing us to determine the critical distance at which the star is totally disrupted, the energy distribution and the fallback rate of the debris, as well as the hydrodynamical evolution of the stellar remnant in the case of a partial disruption. Interestingly, we find that the internal evolution of the remnant's core is strongly influenced by persistent vortices excited in the tidal interaction. These should be sites of strong magnetic field amplification, and the associated mixing may profoundly alter the subsequent evolution of the tidally pruned star.

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Section: Discussionmentioning

confidence: 86%

Hydrodynamical moving-mesh simulations of the tidal disruption of stars by supermassive black holes

Goicovic

Springel

Ohlmann

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The heavier nuclei exist for a main-sequence star with mass more than 1 M ⊙ as well as for a white dwarf (WD) case. Tidal disruption of such a massive star can show a significant enhancement of nitrogen to carbon ratio due to the CNO cycle Gallegos-Garcia et al 2018). These carbon/nitrogen anomalies should, therefore, be observational evidence for TDEs caused by the massive stars.…”

Section: Discussionmentioning

confidence: 99%

Neutrino Emissions from Tidal Disruption Remnants

Hayasaki

Yamazaki

2019

ApJ

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We study high-energy neutrino emissions from tidal disruption remnants around supermassive black holes (SMBHs). The neutrinos are produced by the decay of charged pions originated in ultra-relativistic protons which are accelerated there. In the standard theory of tidal disruption events (TDEs), there are four distinct phases from circularization of stellar debris to superand sub-Eddington accretion flows to radiatively inefficient accretion flows (RI-AFs). In addition, we consider the magnetically arrested disk (MAD) state in both the super-Eddington accretion and RIAF phases. We find that there are three promising cases to produce neutrino emissions: the super-Eddington accretion phase with the MAD state and the RIAF phase with both non-MAD and MAD states. In the super-Eddington MAD state, the enhanced magnetic field makes it possible to accelerate the protons up to an energy of E p,max ∼ 0.35 PeV (M bh /10 7.7 M ⊙ ) 41/48 with the other given appropriate parameters. The neutrino energy estimated at the peak of the energy spectrum is then E ν,pk ∼ 67 TeV (M bh /10 7.7 M ⊙ ) 41/48 . For M bh 10 7.7 M ⊙ , the neutrino light curve is proportional to t −65/24 , while it follows the standard t −5/3 decay rate for M bh < 10 7.7 M ⊙ . In both cases, the neutrino luminosity is nearly Eddington. Such a high luminosity and characteristic light curve diagnose the MAD state in TDEs. In the RIAF phase, we find E p,max ∼ 0.45 PeV (M bh /10 7 M ⊙ ) 5/3 and E ν,pk ∼ 0.35 PeV (M bh /10 7 M ⊙ ) 5/3 , and its light curve is proportional to t −10/3 . This indicates one can identify if the existed RIAFs are the TDE origin or not.Although E p,max ∼ 25 PeV (M bh /10 7 M ⊙ ) −1/12 in the RIAF with the MAD state, the resultant neutrino luminosity is too weak to be detected with IceCube. The tidal disruption remnants are potentially a population of hidden neutrino sources invisible in gamma rays.

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“…Kochanek (2016) predicted abundance anomalies in TDEs resulting from evolved stars. Gallegos-Garcia et al (2018) developed a simple framework, based on the work of Lodato et al (2009) and Kochanek (2016), to calculate the mass fallback rate for the disruption of stars of many masses and ages and to track the composition of the mass fallback. This is a useful framework that can be used to interpret spectroscopic observations of TDEs, but, as we discuss here, the simulations presented in this Letter make several different predictions from it.…”

Section: Introductionmentioning

confidence: 99%

“…The panels from left to right show full disruptions of a middle-age Sun, a TAMS Sun, and a TAMS 3M star. Solid lines are hydrodynamic simulation results and dashed lines are analytic results fromGallegos-Garcia et al (2018).…”

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confidence: 99%

The Tidal Disruption of Sun-like Stars by Massive Black Holes

Law-Smith

Guillochon

Ramírez-Ruiz

2019

ApJL

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We present the first simulations of the tidal disruption of stars with realistic structures and compositions by massive black holes (BHs). We build stars in the stellar evolution code MESA and simulate their disruption in the 3D adaptive-mesh hydrodynamics code FLASH, using an extended Helmholtz equation of state and tracking 49 elements. We study the disruption of a 1M star and 3M star at zero-age main sequence (ZAMS), middle-age, and terminal-age main sequence (TAMS). The maximum BH mass for tidal disruption increases by a factor of ∼2 from stellar radius changes due to MS evolution; this is equivalent to varying BH spin from 0 to 0.75. The shape of the mass fallback rate curves is different from the results for polytropes of Guillochon & Ramirez-Ruiz (2013). The peak timescale t peak increases with stellar age, while the peak fallback rateṀ peak decreases with age, and these effects diminish with increasing impact parameter β. For a β = 1 disruption of a 1M star by a 10 6 M BH, from ZAMS to TAMS, t peak increases from 30 to 54 days, whileṀ peak decreases from 0.66 to 0.14 M /yr. Compositional anomalies in nitrogen, helium, and carbon can occur before the peak timescale for disruptions of MS stars, which is in contrast to predictions from the "frozen-in" model. More massive stars can show stronger anomalies at earlier times, meaning that compositional constraints can be key in determining the mass of the disrupted star. The abundance anomalies predicted by these simulations provide a natural explanation for the spectral features and varying line strengths observed in tidal disruption events.

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Tidal Disruptions of Main-sequence Stars of Varying Mass and Age: Inferences from the Composition of the Fallback Material

Cited by 33 publications

References 51 publications

Hydrodynamical moving-mesh simulations of the tidal disruption of stars by supermassive black holes

Hydrodynamical moving-mesh simulations of the tidal disruption of stars by supermassive black holes

Neutrino Emissions from Tidal Disruption Remnants

The Tidal Disruption of Sun-like Stars by Massive Black Holes

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