Probing Electron-Capture Supernovae: X-Ray Binaries in Starbursts

Abstract

We develop population models of high-mass X-ray binaries (HMXBs) formed after bursts of star formation and we investigate the effect of electron-capture supernovae (ECS) of massive ONeMg white dwarfs and the hypothesis that ECS events are associated with typically low supernova kicks imparted to the nascent neutron stars. We identify an interesting ECS bump in the time evolution of HMXB numbers; this bump is caused by significantly increased production of wind-fed HMXBs 20-60 Myr post-starburst. The amplitude and age extent of the ECS bump depend on the strength of ECS kicks and the mass range of ECS progenitors. We also find that ECSHMXBs form through a specific evolutionary channel that is expected to lead to binaries with Be donors in wide orbits. These characteristics, along with their sensitivity to ECS properties, provide us with an intriguing opportunity to probe ECS physics and progenitors through studies of starbursts of different ages. Specifically, the case of the Small Magellanic Cloud, with a significant observed population of Be-HMXBs and starburst activity 30-60 Myr ago, arises as a promising laboratory for understanding the role of ECS in neutron star formation.

ON THE SPIN PERIOD DISTRIBUTION IN Be/X-Ray BINARIES

“…To examine the influence of different kinds of SNe on the orbital period distribution, we employ a Monte-Carlo method to simulate the formation of BeXBs. We adopt the binary population synthesis (BPS) code developed by Hurley et al (2000Hurley et al ( , 2002 to calculate the evolutions of a large number of the primordial binaries, which is similar to the code StarTrack used by Linden et al (2009). We consider solar abundance for the stars, with most of the input parameters (i.e., the distributions of the orbital separation, mass ratio, the initial mass function of the mass of the primary star) to be the same as the standard ones described by Hurley et al (2002).…”

Double and single recycled pulsars: an evolutionary puzzle?

“…The notion of electron‐capture SNe, which naturally produce such NSs with lower velocity kicks was subsequently introduced by Podsiadlowski et al (2004). More recent evidence for low‐velocity kicks in binary systems has been inferred from the spin–eccentricity correlation seen in DNS binaries (Dewi, Podsiadlowski & Pols 2005; Faulkner et al 2005) and in a starburst activity of high‐mass X‐ray binaries in the Small Magellanic Cloud (Linden et al 2009).…”

The Effect of Starburst Metallicity on Bright X-Ray Binary Formation Pathways

“…This cutoff corresponds both to the first appearances of electron-capture supernovae (ECS; Nomoto 1984;Poelarends et al 2008) in our simulations as well as the last ironcore collapse SN. In Linden et al (2009), we have found that ECS are highly associated with the production of Be-HMXBs. Regardless of the accuracy of this association, we note that McSwain & Gies (2005) found the observed number of Be-HMXBs to be greatest between 25 and 100 Myr after star formation, relegating the vast majority of Be-HMXB activity until after the end of the simulations and the questions considered here.…”