Delayed outflows from black hole accretion tori following neutron star binary coalescence

By R. Fern'andez, B. Metzger. 2013

282 citations recorded by the source corpus.

Expulsion of neutron-rich matter following the merger of neutron star (NS) binaries is crucial to the radioactively-powered electromagnetic counterparts of these events and to their relevance as sources of r-process nucleosynthesis. Here we explore the long-term (viscous) evolution of remnant black hole accretion disks formed in such mergers by means of two-dimensional, time-dependent hydrodynamical simulations. The evolution of the electron fraction due to charged-current weak interactions is included, and neutrino self-irradiation is modeled as a lightbulb that accounts for the disk geometry and moderate optical depth effects. Over several viscous times (~1s), a fraction ~10% of the initial disk mass is ejected as a moderately neutron-rich wind (Y_e ~ 0.2) powered by viscous heating and nuclear recombination, with neutrino self-irradiation playing a sub-dominant role. Although the properties of the outflow vary in time and direction, their mean values in the heavy-element production region are relatively robust to variations in the initial conditions of the disk and the magnitude of its viscosity. The outflow is sufficiently neutron-rich that most of the ejecta forms heavy r-process elements with mass number A >130, thus representing a new astrophysical source of r-process nucleosynthesis, distinct from that produced in the dynamical ejecta. Due to its moderately high entropy, disk outflows contain a small residual fraction ~1% of helium, which could produce a unique spectroscopic signature.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a26758eb968d0354418719621d30172fd35dd3c4

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Citations in the corpus

r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE (2015, background): “…tidally (Lattimer et al. 1977; Freiburghaus et al. 1999), dynamically from the region where the two neutron stars collide (Bauswein et al. 2013; Hotokezaka et al. 2013a), or from the accretion disk that forms after the merger (Fernández & Metzger 2013; Perego et al. 2014; Just et al. 2015).”
RADIOACTIVITY AND THERMALIZATION IN THE EJECTA OF COMPACT OBJECT MERGERS AND THEIR IMPACT ON KILONOVA LIGHT CURVES (2016, background): “05 0.1– ) as a wind from an accretion torus (Fernández & Metzger 2013; Perego et al. 2014; Fernández et al. 2015; Just et al. 2015).”
A Magnetar Origin for the Kilonova Ejecta in GW170817 (2018, background): “1–1 s (e.g., Metzger et al. 2008b) or an accretion disk of lifetime ∼1 s (e.g., Fernández & Metzger 2013), and is not a unique prediction of a (failed or successful) ultrarelativistic jet (Gottlieb et al. 2018).”
Kilonova light curves from the disc wind outflows of compact object mergers (2014, methodology): “Viscous and nuclear heating during accretion can drive winds that unbind a significant fraction of the disc (Lee, Ramirez-Ruiz & López-Cámara 2009; Fernández & Metzger 2013a; Just et al. 2015).”
Constraining the Maximum Mass of Neutron Stars from Multi-messenger Observations of GW170817 (2017, background): “Furthermore, the predicted velocities of the disk winds ∼ 0.03 − 0.1c (e.g. Fernández & Metzger 2013; Just et al. 2015) are 4 lower than the velocities & 0.2 − 0.3c inferred for the blue KN of GW170817 (e.g. Nicholl et al. 2017).”
Red or blue? A potential kilonova imprint of the delay until black hole formation following a neutron star merger (2014, background): “The code contains modifications relative to the public version, aimed at investigating the viscous evolution of merger remnant accretion discs (Fernández 2012; Fernández & Metzger 2013b; FM13).”
RADIATIVE TRANSFER SIMULATIONS OF NEUTRON STAR MERGER EJECTA (2013, background): “These relatively light elements can be abundant if the wind or outflow from a black hole torus, which can subsequently occur after the NS merger, dominates the ejecta (Wanajo & Janka 2012; Fernández & Metzger 2013).”
The cocoon emission - an electromagnetic counterpart to gravitational waves from neutron star mergers (2017, background): “Numerical simulations (e.g. Rosswog et al. 1998; Hotokezaka et al. 2011; Fernández & Metzger 2013; Hotokezaka et al. 2013b; Bauswein et al. 2013; Rosswog 2013; Perego et al. 2014a; Siegel et al. 2014; Wanajo et al. 2014; Just et al. 2015) suggest that the mergers are accompanied by significant mass…”
Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817 (2017, background): “After the dynamical ejection, there may also be additional mass ejection (“postmerger” ejecta or “wind” ejecta) by viscous heating and neutrino heating (e.g., Dessart et al. 2009; Fernández & Metzger 2013; Perego et al. 2014; Shibata et al. 2017).”
Neutron-powered precursors of kilonovae (2014, background): “…consequence of the merger process appears to be the ejection of neutron rich matter, either during the early, short-lived dynamical phase (e.g. Goriely et al. 2011) or in delayed outflows from the remnant accretion torus (e.g. Fernández & Metzger 2013; Perego et al. 2014; Just et al. 2014).”
Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers (2017, methodology): “The BH accretion disk is such that the inner regions (r 107 cm) also approach beta equilibrium, but most of the material that reaches high Ye is accreted onto the BH (cf. Figure 6 of Fernández & Metzger 2013).”
Comprehensive nucleosynthesis analysis for ejecta of compact binary mergers (2014, methodology): “We ignore the effects of heavy-lepton neutrinos, which are of minor relevance during the torus evolution (e.g. Janka et al. 1999; Ruffert & Janka 1999; Deaton et al. 2013; Fernández & Metzger 2013; Foucart et al. 2014).”
Neutrino-driven winds from neutron star merger remnants (2014, background): “D, 88, 041503 Lattimer J. M., Schramm D. N., 1974, ApJ, 192, L145 Lattimer J. M., Schramm D. N., 1976, ApJ, 210, 549 Lattimer J. M., Mackie F., Ravenhall D. G., Schramm D. N., 1977, ApJ, 213, 225 Lee W. H., Ramirez-Ruiz E., 2007, New J. Phys., 9, 17 Lee W. H., Ramirez-Ruiz E., López-Cámara D., 200”
The long-term evolution of neutron star merger remnants – I. The impact of r-process nucleosynthesis (2013, background): “Recent work (Fernández & Metzger 2013) suggests that ∼ 10−2 M become unbound with Ye ∼ 0.2, in addition to the dynamic ejecta and the wind material.”
Neutron-star Radius Constraints from GW170817 and Future Detections (2017, background): “Also, the different nature of the merger remnant yields different amounts of secular ejecta (Fernández & Metzger 2013; Metzger & Fernández 2014; Perego et al. 2014; Siegel et al. 2014; Just et al. 2015).”
NEUTRINO-DRIVEN WINDS IN THE AFTERMATH OF A NEUTRON STAR MERGER: NUCLEOSYNTHESIS AND ELECTROMAGNETIC TRANSIENTS (2015, methodology): “In contrast to previous studies (i.e., Fernández & Metzger (2013); Just et al. (2015a)) with a black hole as central object, we assume a long-lived MNS.”