The University of Southampton
University of Southampton Institutional Repository

The observed vs total population of ULXs

The observed vs total population of ULXs
The observed vs total population of ULXs
We have analyzed how anisotropic emission of radiation affects the observed sample of ultraluminous X-ray sources (ULXs) by performing simulations of the evolution of stellar populations, employing recent developments in stellar and binary physics, and by utilizing a geometrical beaming model motivated by theory and observation. While ULXs harboring black hole accretors (BH ULXs) are typically emitting isotropically, the majority of ULXs with neutron star accretors (NS ULXs) are found to be beamed. These findings confirm previous assertions that a significant fraction of ULXs are hidden from view due to a substantial misalignment of the emission beam and the line of sight. We find the total number of NS ULXs in regions with constant star formation (SF), solar metallicity, and ages above $\sim 1\,\mathrm{Gyr}$ to be higher than the BH ULXs, although observationally both populations are comparable. For lower metallicities, BH ULX dominate both the total and observed ULX populations. As far as burst SF is concerned, young ULX populations are dominated by BH ULXs, but this changes as the population ages and, post SF, NS ULXs dominate both the observed and total ULX populations. We also compare our simulation output to a previous analytical prediction for the relative ratio of BH to NS ULXs in idealized flux-limited observations and find broad agreement for all but the lowest metallicities. In so doing, we find that in such surveys the observed ULX population should be heavily dominated by black hole systems rather than by systems containing neutron stars.
1538-3881
Wiktorowicz, Grzegorz
f2277210-4d99-4441-aa25-c5d324dfda2b
Lasota, Jean-Pierre
47fcca7a-1082-415e-94e0-df546c4f49fc
Middleton, Matthew
f91b89d9-fd2e-42ec-aa99-1249f08a52ad
Belczynski, Krzysztof
1c9afedb-121c-4151-af65-939932c3f4c5
Wiktorowicz, Grzegorz
f2277210-4d99-4441-aa25-c5d324dfda2b
Lasota, Jean-Pierre
47fcca7a-1082-415e-94e0-df546c4f49fc
Middleton, Matthew
f91b89d9-fd2e-42ec-aa99-1249f08a52ad
Belczynski, Krzysztof
1c9afedb-121c-4151-af65-939932c3f4c5

Wiktorowicz, Grzegorz, Lasota, Jean-Pierre, Middleton, Matthew and Belczynski, Krzysztof (2019) The observed vs total population of ULXs. The Astronomical Journal, 875 (1), [53]. (doi:10.3847/1538-4357/ab0f27).

Record type: Article

Abstract

We have analyzed how anisotropic emission of radiation affects the observed sample of ultraluminous X-ray sources (ULXs) by performing simulations of the evolution of stellar populations, employing recent developments in stellar and binary physics, and by utilizing a geometrical beaming model motivated by theory and observation. While ULXs harboring black hole accretors (BH ULXs) are typically emitting isotropically, the majority of ULXs with neutron star accretors (NS ULXs) are found to be beamed. These findings confirm previous assertions that a significant fraction of ULXs are hidden from view due to a substantial misalignment of the emission beam and the line of sight. We find the total number of NS ULXs in regions with constant star formation (SF), solar metallicity, and ages above $\sim 1\,\mathrm{Gyr}$ to be higher than the BH ULXs, although observationally both populations are comparable. For lower metallicities, BH ULX dominate both the total and observed ULX populations. As far as burst SF is concerned, young ULX populations are dominated by BH ULXs, but this changes as the population ages and, post SF, NS ULXs dominate both the observed and total ULX populations. We also compare our simulation output to a previous analytical prediction for the relative ratio of BH to NS ULXs in idealized flux-limited observations and find broad agreement for all but the lowest metallicities. In so doing, we find that in such surveys the observed ULX population should be heavily dominated by black hole systems rather than by systems containing neutron stars.

Text
The Observed versus Total Population of ULXs - Accepted Manuscript
Download (1MB)

More information

Accepted/In Press date: 11 March 2019
e-pub ahead of print date: 16 April 2019
Published date: 16 April 2019
Additional Information: arXiv document is AM

Identifiers

Local EPrints ID: 430986
URI: http://eprints.soton.ac.uk/id/eprint/430986
ISSN: 1538-3881
PURE UUID: 1badb350-5ead-4f55-93bd-a4e1d8b2b1d5

Catalogue record

Date deposited: 21 May 2019 16:30
Last modified: 07 Oct 2020 04:51

Export record

Altmetrics

Contributors

Author: Grzegorz Wiktorowicz
Author: Jean-Pierre Lasota
Author: Krzysztof Belczynski

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×