文章基本信息

标题：Limits on thickness and efficiency of Polish doughnuts in application to the ULX sources
本地全文：下载
作者：M. Wielgus ; M. Wielgus ; W. Yan 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2016
卷号：587
页码：1-7
DOI：10.1051/0004-6361/201527878
语种：English
出版社：EDP Sciences
摘要：Polish doughnuts (PDs) are geometrically thick disks that rotate with super-Keplerian velocities in their innermost parts, and whose long and narrow funnels along rotation axes collimate the emerging radiation into beams. In this paper we construct an extremal family of PDs that maximize both geometrical thickness and radiative efficiency. We then derive upper limits for these quantities and subsequently for the related ability to collimate radiation. PDs with such extreme properties may explain the observed properties of ultraluminous X-ray sources without the need for the black hole masses to exceed ~10 M⊙. However, we show that strong advective cooling, which is expected to be one of the dominant cooling mechanisms in accretion flows with super-Eddington accretion rates, tends to reduce the geometrical thickness and luminosity of PDs substantially. We also show that the beamed radiation emerging from the PD funnels corresponds to isotropic luminosities that obey Lcol ≈ 0.1Ṁc2 for Ṁ ≫ ṀEdd, and not the familiar and well-known logarithmic relation, L ~ lnṀ.
关键词：accretion, accretion disks;stars: jets;stars: black holes;black hole physics;X-rays: bursts;stars: neutron