Title: Relativistic Tidal Disruption and Nuclear Ignition of White Dwarf Stars by Intermediate-mass Black Holes

Abstract

We introduce results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate-mass black holes. We view the evolution of 0.2 M_⊙ and 0.6 M_⊙ stars on parabolic trajectories that approach 10³–10⁴ M_⊙ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect that tidal disruption has on thermonuclear reactions and the synthesis of intermediate-mass to heavy elements. These encounters create diverse thermonuclear environments that are characteristic of Type I supernovae and capable of producing both intermediate-mass and heavy elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths β ~ 2.6 and large periapsis radius R P ~ 28 Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium-group to iron-group elements and tidal strength, with β ≲ 5 producing predominantly calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium-group elements to <15% of available nuclear fuel. Iron-group elements, yet, continue to be produced in greater quantity and ratio with increasing tidal strength,more » peaking at ~60% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1–0.7 Hz and strain amplitudes from 0.5 × 10^–22 to 3.5 × 10^–22 at a source distance of 10 Mpc.« less

Authors:

Anninos, Peter ^[1]; Fragile, P. Chris  ^[2];

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Olivier, Samuel S. ^[3]; Hoffman, Robert ^[1]; Mishra, Bhupendra ^[4]; Camarda, Karen ^[5]

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+ Show Author Affiliations

1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. College of Charleston, SC (United States); Univ. of California, Santa Barbara, CA (United States)
3. Univ. of California, Berkeley, CA (United States)
4. Univ. of California, Santa Barbara, CA (United States); Univ. of Colorado, Boulder, CO (United States); National Inst. of Standards and Technology (NIST), Boulder, CO (United States)
5. Washburn Univ., Topeka, KS (United States)

Publication Date:

Mon Sep 17 00:00:00 EDT 2018

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)

OSTI Identifier:

1557032

Report Number(s):

LLNL-JRNL-752874
Journal ID: ISSN 1538-4357; 938505

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

The Astrophysical Journal (Online)

Additional Journal Information:

Journal Name: The Astrophysical Journal (Online); Journal Volume: 865; Journal Issue: 1; Journal ID: ISSN 1538-4357

Publisher:

Institute of Physics (IOP)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; black hole physics; hydrodynamics; nuclear reactions; nucleosynthesis; abundances; stars: black holes; white dwarfs