Hard X-ray Bursts from Collapse of the Super Massive Stars

TL;DR

This paper explores the potential observability of high-energy X-ray bursts from super massive star collapses, suggesting they could produce long-lasting, soft-spectrum gamma-ray bursts detectable with future long-term observations.

Contribution

It introduces the concept of observing X-ray bursts from super massive collapsars, detailing their energy output, duration, and spectral characteristics, which are distinct from typical gamma-ray bursts.

Findings

Jets with power up to 10^{51} erg/s can be produced.

Bursts could last around 10^5 seconds due to high redshift.

Event rate estimated at 0.03 per year, detectable with long-term monitoring.

Abstract

The very first stars in the Universe can be very massive, up to $10^6M_\odot$. They would leave behind massive black holes that could act as seeds for growing super massive black holes of active galactic nuclei. Given the anticipated fast rotation such stars would end their live as super massive collapsars and drive powerful magnetically-dominated jets. In this paper we investigate the possibility of observing the bursts of high-energy emission similar to the Long Gamma Ray Bursts associated with normal collapsars. We show that during the collapse of supercollapsars, the Blandford-Znajek mechanism can produce jets as powerful as few$\times10^{51}$erg/s and release up to $10^{56}$erg of the black hole rotational energy. Due to the higher intrinsic time scale and higher redshift the initial bright phase of the burst can last for about $10^5$ seconds whereas the central engine would remain active for about 10 days. Due to the high redshift the burst spectrum is expected to be soft, with the spectral energy distribution peaking at around 60keV. The peak total flux density is relatively low, few$\times 10^{-7}erg\, cm^{-2} s^{-1}$, but not prohibitive. The such events should be rear 0.03 year$^{-1}$, the observations needs long term program and could be done in future.