Kilonova rates from spherical and axisymmetrical models

Abstract

Detecting the thermal emission from double neutron star merger events is a challenging task because of the quick fading of the observed flux. In order to create an efficient observing strategy for their observing method, it is crucial to know their intrinsic rate. Unfortunately, the numerous models existing today predict this rate on a very wide range. Hence, our goal in this paper is to investigate the effect of different levels of approximations on the relative rate predictions. Also, we study the effect of distinct ejecta mass layouts on the light curve. We find that the ratio of the expected kilonova detections of the spherical to axisymmetrical models is 6:1 (or 2:1, depending on the input parameter set applied in our work). Nevertheless, the light-curve shape is only slightly affected by the various ejecta alignments. This means that different ejecta layouts can produce light curves with similar shapes making it a challenging task to infer the structure of the matter outflow. Thus, we conclude that the uncertainty in the rate predictions arising from the various ejecta mass distribution models is negligible compared to the errors present in other input parameters (e.g. binary neutron star merger rate). In addition, we show that up to moderate redshifts (z ≲ 0.2) the redshift distribution type (observed or uniform in volume) does not affect the expected relative rate estimations.

Kilonova Emission From Black Hole-Neutron Star Mergers. II. Luminosity Function and Implications for Target-of-opportunity Observations of Gravitational-wave Triggers and Blind Searches

“…Overall, the comprehensive characteristics of a kilonova depend on many factors, including the central remnant after the merger, physical properties of the ejected material, and potential additional energy injection. The asymmetric geometry of the ejecta also provides viewing-angle-dependent properties of kilonova lightcurves and polarization properties (Kasen et al 2015;Bulla et al 2019Bulla et al , 2020Kawaguchi et al 2020;Korobkin et al 2020;Zhu et al 2020;Darbha & Kasen 2020;Kóbori et al 2020).…”

Estimating GRBs' cosmological distances

“…The collapsing events are typically longer and softer than the star merging ones. A third group was identified by Horváth (1998) based on the duration-hardness plane (Horváth et al, 2004(Horváth et al, , 2006Kóbori et al, 2020). The physical model of this intermediate group could not be perfectly determined but it seems that the X-ray flash events could have a connection to the intermediate GRBs (Horváth et al, 2010;Veres et al, 2010;Pinter et al, 2017;Bi et al, 2018).…”

Comparing inclination dependent analyses of kilonova transients

“…In this paper, we will use several different KN geometries and the radiative transfer code POSSIS developed by Bulla (2019) to understand how inclination constraints on GW170817/AT2017gfo depend on the underlying geometry assumed, extending the work of Dhawan et al (2019) and complementary to the work of Kóbori et al (2020). In Section 2, we discuss the creation of surrogate models based on KN geometries inspired by Kasen et al (2017), Wollaeger et al (2018) and Bulla (2019).…”