Constraints on the ejecta of the GW170817 neutron star merger from its electromagnetic emission

Waxman, Eli; Ofek, E. O.; Kushnir, Doron; Gal‐Yam, A.

doi:10.1093/mnras/sty2441

Cited by 179 publications

(209 citation statements)

References 79 publications

Supporting

Mentioning

189

Contrasting

Order By: Relevance

“…It also does not conflict with the estimation of M ej ∼10 −3 -10 −2 M e for the dynamical ejecta of GW170817 (Abbott et al 2017d;Utsumi et al 2017;Tanaka et al 2017;Matsumoto et al 2018). In a few recent studies, a more precise ejecta mass of M ej ∼0.05M e was estimated when modeling the GW170817 kilonova (Cowperthwaite et al 2017;Drout et al 2017;Kasliwal et al 2017;Kasen et al 2017;Villar et al 2017;Waxman et al 2017). These studies also support the idea that there is enough material being ejected during the NS-NS merger.…”

Section: Numerical Resultssupporting

confidence: 59%

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

Huang

et al. 2018

ApJL

View full text Add to dashboard Cite

The brightness of the multi-wavelength afterglow of GRB 170817A is increasing unexpectedly even ∼160 days after the associated gravitational burst. Here we suggest that the brightening can be caused by a late-time energy injection process. We use an empirical expression to mimic the evolution of the injection luminosity, which consists of a power-law rising phase and a power-law decreasing phase. It is found that the power-law indices of the two phases are 0.92 and −2.8, respectively, with the peak time of the injection being ∼110days. The energy injection could be due to some kind of accretion, with the total accreted mass being ∼0.006M e . However, normal fall-back accretion, which usually lasts for a much shorter period, cannot provide a natural explanation. Our best-fit decay index of −2.8 is also at odds with the expected value of −5/3 for normal fall-back accretion. Noting that the expansion velocities of the kilonova components associated with GW170817 are 0.1-0.3 c, we argue that there should also be some ejecta with correspondingly lower velocities during the coalescence of the double neutron star (NS) system. They are bound by the gravitational well of the remnant central compact object and might be accreted at a timescale of about 100 days, providing a reasonable explanation for the energy injection. Detailed studies on the long-lasting brightening of GRB 170817A thus may provide useful information on matter ejection during the merger process of binary neutron stars.

show abstract

Section: Numerical Resultssupporting

confidence: 59%

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

Huang

et al. 2018

ApJL

View full text Add to dashboard Cite

show abstract

“…Several comments are in place here regarding the differences between the Ia SN case discussed in this paper and the kilonova case discussed by Waxman, et al (2018); Waxman, Ofek & Kushnir (2019). First, the characteristic density of the ejecta is some four orders of magnitude lower in the kilonave case, due to the smaller ejecta mass and its higher velocity.…”

Section: Summary and Discussionmentioning

confidence: 77%

Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light-curve flattening

Kushnir

Waxman

2020

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

The finite time, τ dep , over which positrons from β + decays of 56 Co deposit energy in type Ia supernovae ejecta lead, in case the positrons are trapped, to a slower decay of the bolometric luminosity compared to an exponential decline. Significant light-curve flattening is obtained when the ejecta density drops below the value for which τ dep equals the 56 Co lifetime. We provide a simple method to accurately describe this "delayed deposition" effect, which is straightforward to use for analysis of observed light curves. We find that the ejecta heating is dominated by delayed deposition typically from 600 to 1200 day, and only later by longer lived isotopes 57 Co and 55 Fe decay (assuming solar abundance). For the relatively narrow 56 Ni velocity distributions of commonly studied explosion models, the modification of the light curve depends mainly on the 56 Ni mass-weighted average density, ρ t 3 . Accurate late-time bolometric light curves, which may be obtained with JWST far-infrared (far-IR) measurements, will thus enable to discriminate between explosion models by determining ρ t 3 (and the 57 Co and 55 Fe abundances). The flattening of light curves inferred from recent observations, which is uncertain due to the lack of far-IR data, is readily explained by delayed deposition in models with ρ t 3 ≈ 0.2 M ⊙ (10 4 km s −1 ) −3 , and does not imply supersolar 57 Co and 55 Fe abundances.

show abstract

“…We use the complete stopping cross section formula, with the logarithmic factor (see figure 2); therefore, the time dependence of our late-time electron heating rate agrees with that obtained by Waxman et al (2019). Waxman et al (2018) interpret a break in the observed bolometric light curve of the GW170817 macronova around ∼ 6 days as the thermalization break, which is a transition of the electron heating rate from the regime ofQ th,e ∝ t −1.3 to ∝ t −2.8 . This scenario requires that the thermalization break occurs at relatively early time and that it is rather sharp.…”

Section: Thermalizationmentioning

confidence: 97%

Radioactive Heating Rate of r-process Elements and Macronova Light Curve

Hotokezaka

Nakar

2020

ApJ

100

View full text Add to dashboard Cite

We study the heating rate of r-process nuclei and thermalization of decay products in neutron star merger ejecta and macronova (kilonova) light curves. Thermalization of charged decay products, i.e., electrons, α-particles, and fission fragments is calculated according to their injection energy. The γ-ray thermalization processes are also properly calculated by taking the γ-ray spectrum of each decay into account. We show that the β-decay heating rate at later times approaches a powerlaw decline as ∝ t −2.8 , which agrees with the result of Waxman et al. (2019). We present a new analytic model to calculate macronova light curves, in which the density structure of the ejecta is accounted for. We demonstrate that the observed bolometric light curve and temperature evolution of the macronova associated with GW170817 are reproduced well by the β-decay heating rate with the solar r-process abundance pattern. We interpret the break in the observed bolometric light curve around a week as a result of the diffusion wave crossing a significant part of the ejecta rather than a thermalization break. We also show that the time-weighted integral of the bolometric light curve (Katz integral) is useful to provide an estimate of the total r-process mass from the observed data, which is independent of the highly uncertain radiative transfer. For the macronova in GW170817, the ejecta mass is robustly estimated as ≈ 0.05M for A min ≤ 72 and 85 ≤ A min ≤ 130 with the solar r-process abundance pattern. The code for computation of the heating rate and light curve for given initial nuclear abundances is publicly available.

show abstract

Constraints on the ejecta of the GW170817 neutron star merger from its electromagnetic emission

Cited by 179 publications

References 79 publications

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light-curve flattening

Radioactive Heating Rate of r-process Elements and Macronova Light Curve

Contact Info

Product

Resources

About