Mass ejection from neutron star mergers: different components and expected radio signals

Hotokezaka, Kenta; Piran, Tsvi

doi:10.1093/mnras/stv620

Cited by 131 publications

(139 citation statements)

References 72 publications

(109 reference statements)

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“…The deceleration of this fast material by its shock interaction with the circumburst medium produces synchrotron emission peaking at MHz to GHz frequencies (Nakar & Piran 2011;Metzger & Bower 2014;Hotokezaka & Piran 2015). The synchrotron model provides a mapping from the flux densities to physical parameters of the magnetar and circumburst environment: the magnetar's rotational energy (E rot ), ejecta mass (M ej ), circumburst density (n), fractions of post-shock energy in radiating electrons (ò e ) and magnetic fields (ò B ), and the electron power-law distribution index (p) that describes the input distribution of electrons with…”

Section: Magnetar Modelmentioning

confidence: 99%

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Fong

Metzger

Berger

et al. 2016

ApJ

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The merger of a neutron star (NS) binary may result in the formation of a rapidly spinning magnetar. The magnetar can potentially survive for seconds or longer as a supramassive NS before collapsing to a black hole if, indeed, it collapses at all. During this process, a fraction of the magnetar's rotational energy of ∼10 53 erg is transferred via magnetic spin-down to the surrounding ejecta. The resulting interaction between the ejecta and the surrounding circumburst medium powers a year-long or greater synchrotron radio transient. We present a search for radio emission with the Very Large Array following nine short-duration gamma-ray bursts (GRBs) at rest-frame times of ≈1.3-7.6 yr after the bursts, focusing on those events that exhibit early-time excess X-ray emission that may signify the presence of magnetars. We place upper limits of 18-32 μJy on the 6.0 GHz radio emission, corresponding to spectral luminosities of (0.05-8.3)×10 39 erg s −1 . Comparing these limits to the predicted radio emission from a long-lived remnant and incorporating measurements of the circumburst densities from broadband modeling of short GRB afterglows, we rule out a stable magnetar with an energy of 10 53 erg for half of the events in our sample. A supramassive remnant that injects a lower rotational energy of 10 52 erg is ruled out for a single event, GRB 050724A. This study represents the deepest and most extensive search for long-term radio emission following short GRBs to date, and thus the most stringent limits placed on the physical properties of magnetars associated with short GRBs from radio observations.

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Section: Magnetar Modelmentioning

confidence: 99%

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Fong

Metzger

Berger

et al. 2016

ApJ

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“…Furthermore, follow-up observations with UV, optical, and infrared telescopes found a kilonova (Abbott et al 2017a;Arcavi et al 2017;Coulter et al 2017;Cowperthwaite et al 2017;Smartt et al 2017;Tanaka et al 2017;Valenti et al 2017) emitting from the mildly relativistic ejecta (Lattimer & Schramm 1974;Rosswog et al 1999;Hotokezaka et al 2013) as expected in advance (Li & Paczyński 1998;Metzger et al 2010;Tanaka & Hotokezaka 2013). The ejected material will form a shock propagating in the circumbinary medium (CBM), and electromagnetic signals on a timescale of a few years have been predicted (Nakar & Piran 2011;Piran et al 2013;Rosswog et al 2013;Takami et al 2014;Hotokezaka & Piran 2015;Hotokezaka et al 2016). Electrons are accelerated at the shock and emit nonthermal synchrotron photons from the radio to X-ray range, which is the mildly relativistic counterpart to the emission from the supernova remnant (nonrelativistic) or the gamma-ray burst (GRB) afterglow (ultrarelativistic).…”

Section: Introductionmentioning

confidence: 99%

Subsequent Nonthermal Emission Due to the Kilonova Ejecta in GW170817

Asano¹,

To²

2018

ApJ

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The ejected material at the binary neutron star merger GW 170817 was confirmed as a kilonova by UV, optical, and IR observations. This event provides a unique opportunity to investigate the particle acceleration at a mildly relativistic shock propagating in the circumbinary medium. In this paper, we simulate the nonthermal emission from electrons accelerated by the shock induced by the kilonova ejecta with a time-dependent method. The initial velocity and mass of the ejecta in the simulations are obtained from the kilonova observations in GW 170817. If the ambient density is high enough (≥ 10 −2 cm −3 ), radio, optical/IR, and X-ray signals will be detected in a few years, though the off-axis short gamma-ray burst models, accounting for the X-ray/radio counterpart detected at ∼ 10 days after the merger, implies low ambient density. We also demonstrate that the additional low-mass (∼ 10 −5 M ⊙ ) component with a velocity of 0.5c-0.8c can reproduce the early X-ray/radio counterpart. This alternative model allows a favorably high density to detect the nonthermal emission due to the kilonova ejecta. Even for a low ambient density such as ∼ 10 −3 cm −3 , depending on the microscopic parameters for the electron acceleration, we can expect a growth of radio flux of ∼ 0.1 mJy in a few years.

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“…Faber et al 2006;Nakar 2007;Giacomazzo et al 2013;Berger 2014;Ruiz et al 2016;Kathirgamaraju et al 2017), cocoon prompt emission (Gottlieb et al 2017a;Lazzati et al 2017a,b;Nakar & Piran 2017), jet/cocoon afterglows (e.g. Gottlieb et al 2017a;Lamb & Kobayashi 2017;Lazzati et al 2017a;Nakar & Piran 2017), and kilonovae (also referred to as "macronovae", Li & Paczyński 1998;Kulkarni 2005;Metzger et al 2010;Metzger & Berger 2012;Kasen et al 2013;Hotokezaka & Piran 2015;Gottlieb et al 2017a;Nakar & Piran 2017). A late-time (year-scaled) radio signal might originate from the ejectamedium interaction as the ejecta enters the Sedov-Taylor phase (Nakar & Piran 2011).…”

Section: Introductionmentioning

confidence: 99%

Afterglows and Kilonovae Associated with Nearby Low-luminosity Short-duration Gamma-Ray Bursts: Application to GW170817/GRB 170817A

Xiao

Liu

Dai

et al. 2017

ApJL

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Very recently, the gravitational wave (GW) event GW170817 was discovered to be associated with the short gamma-ray burst (GRB) 170817A. Multi-wavelength follow-up observations were carried out, and X-ray, optical and radio counterparts to GW170817 were detected. The observations undoubtedly indicate that GRB170817A originates from a binary neutron star (BNS) merger. However, the GRB falls into the low-luminosity class which could have a higher statistical occurrence rate and detection probability than the normal (high-luminosity) class. This implies a possibility that GRB170817A is intrinsically powerful but we are off-axis and only observe its side emission. In this paper, we provide a timely modeling of the multi-wavelength afterglow emission from this GRB and the associated kilonova signal from the merger ejecta, under the assumption of a structured jet, a two-component jet, and an intrinsically less-energetic quasi-isotropic fireball respectively. Comparing the afterglow properties with the multi-wavelength follow-up observations, we can distinguish between these three models. Furthermore, a few model parameters (e.g., the ejecta mass and velocity) can be constrained.

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Mass ejection from neutron star mergers: different components and expected radio signals

Cited by 131 publications

References 72 publications

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Subsequent Nonthermal Emission Due to the Kilonova Ejecta in GW170817

Afterglows and Kilonovae Associated with Nearby Low-luminosity Short-duration Gamma-Ray Bursts: Application to GW170817/GRB 170817A

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