Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Bayesian parameter constraints for neutron star masses and radii using X-ray timing observations of accretion-powered millisecond pulsars
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Tuorla Observatory, Department of Physics and Astronomy, 20014 University of Turku, Finland e-mail: thjsal@utu.fi; Space Research Institute of the Russian Academy of Sciences, Profsoyuznaya str. 84/32, 117997 Moscow, Russia .
2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 618, article id 33348Article in journal (Refereed) Published
Abstract [en]

We present a Bayesian method to constrain the masses and radii of neutron stars (NSs) using the information encoded in the X-ray pulse profiles of accreting millisecond pulsars. We model the shape of the pulses using "oblate Schwarzschild" approximation, which takes into account the deformed shape of the star together with the special and general relativistic corrections to the photon trajectories and angles. The spectrum of the radiation is obtained from an empirical model of Comptonization in a hot slab in which a fraction of seed black-body photons is scattered into a power-law component. By using an affine-invariant Markov chain Monte Carlo ensemble sampling method, we obtain posterior probability distributions for the different model parameters, especially for the mass and the radius. To test the robustness of our method, we first analysed self-generated synthetic data with known model parameters. Similar analysis was then applied for the observations of SAX J1808.4-3658 by the Rossi X-ray Timing Explorer (RXTE). The results show that our method can reproduce the model parameters of the synthetic data, and that accurate constraints for the radius can be obtained using the RXTE pulse profile observations if the mass is a priori known. For a mass in the range 1.5-1.8 M, the radius of the NS in SAX J1808.4-3658 is constrained between 9 and 13 km. If the mass is accurately known, the radius can be determined with an accuracy of 5% (68% credibility). For example, for the mass of 1.7 M the equatorial radius is Req = 11.9+0.5 -0.4 km. Finally, we show that further improvements can be obtained when the X-ray polarization data from the Imaging X-ray Polarimeter Explorer will become available.

Place, publisher, year, edition, pages
EDP Sciences , 2018. Vol. 618, article id 33348
Keywords [en]
Pulsars: individual: SAX J1808.4-3658, Stars: neutron, X-rays: binaries, X-rays: stars, Bayesian networks, Markov processes, Monte Carlo methods, Neutrons, Photons, Probability distributions, Pulsars, Timing circuits, Markov Chain Monte-Carlo, Parameter constraints, Pulsars: individuals, Relativistic correction, Stars: neutrons, X rays: stars, X-ray timing explorers, X rays
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-247153DOI: 10.1051/0004-6361/201833348ISI: 000448352600001Scopus ID: 2-s2.0-85056121372OAI: oai:DiVA.org:kth-247153DiVA, id: diva2:1313984
Note

QC 20190507

Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-05-07Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Nättilä, JoonasPoutanen, Juri

Search in DiVA

By author/editor
Nättilä, JoonasPoutanen, Juri
By organisation
Nordic Institute for Theoretical Physics NORDITA
In the same journal
Astronomy and Astrophysics
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf