Hard X-Ray bursts in collapse of supermassive stars

• Published in: Astrophysical bulletin 2010-07, Vol.65 (3), p.217-222
• Main Author: Barkov, M. V.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Astrophysics and Cosmology; Gamma ray astronomy; Physics; Physics and Astronomy; Stars & galaxies; X-ray astronomy
• ISSN: 1990-3413; 1990-3421
• DOI: 10.1134/S1990341310030028

The first stars in the Universe were verymassive, with masses as large as 10 6 M ⊙ . They evolved into massive black holes (BH), which could have become the grains of the formation of supermassive BH in active galactic nuclei. If a supermassive star (SMS) rapidly rotates, it ends up as a supermassive collapsar and produces a magnetically accelerated jet. In this paper we discuss the possibility of the detection of hard X-ray bursts similar to gamma-ray bursts, which are associated with normal collapsars [1]. We demonstrate that in the process of the formation of a supecollapsar a jet may form via the Blandford-Znajek mechanism. The power of the jet may be as high as several 10 51 erg/s and the total energy of the outburst may amount to 10 56 erg. Due to the long time scales and large redshifts, the initial bright phase of the burstmay last for about 10 5 s, whereas the activity time of the central engine may be as long as 10 days. The large redshifts should make the spectrum softer compared to those of common gamma-ray bursts. The maximum of the spectral distribution should lie near 60 keV. The maximum flux is relatively small-on the order of several 10 −7 erg/(cm −2 s)-but quite detectable. Such events for SMS should be rather rare: their occurence frequency must be of about 0.03/yr. Observations are to be carried out as long-term programs and will possibly be made in the future.