Simultaneous NICER and NuSTAR observations of the ultracompact x-ray binary 4u 1543-624

Ludlam RM, Jaodand AD, Garcia J, Degenaar N, Tomsick JA, Cackett EM, Fabian AC, Gandhi P, Buisson DJK, Shaw AW, Chakrabarty D (2021)

Publication Type: Journal article

Publication year: 2021

Journal

Astrophysical Journal American Astronomical Society

Book Volume: 911

Article Number: abedb0

Journal Issue: 2

DOI: 10.3847/1538-4357/abedb0

Abstract

We present the first joint NuSTAR and NICER observations of the ultracompact X-ray binary (UCXB) 4U 1543 -624 obtained in 2020 April. The source was at a luminosity of L0.5-50 keV = 4.9(D/7 kpc)2 × 1036 erg s-1 and showed evidence of reflected emission in the form of an O VIII line, Fe K line, and Compton hump within the spectrum. We used a full reflection model, known as XILLVERCO, that is tailored for the atypical abundances found in UCXBs, to account for the reflected emission. We tested the emission radii of the O and Fe line components and conclude that they originate from a common disk radius in the innermost region of the accretion disk (Rin . 1.07 RISCO). Assuming that the compact accretor is a neutron star (NS) and the position of the inner disk is the Alfvén radius, we placed an upper limit on the magnetic field strength to be B . 0.7(D/7 kpc) × 108 G at the poles. Given the lack of pulsations detected and position of Rin, it was likely that a boundary layer region had formed between the NS surface and inner edge of the accretion disk with an extent of 1.2 km. This implies a maximum radius of the neutron star accretor of RNS . 12.1 km when assuming a canonical NS mass of 1.4Me.

Authors with CRIS profile

Javier Garcia Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut

Involved external institutions

University of California, Berkeley US United States (USA) (US) California Institute of Technology (Caltech) US United States (USA) (US) University of Amsterdam NL Netherlands (NL) Wayne State University (WSU) US United States (USA) (US) University of Cambridge GB United Kingdom (GB) University of Southampton GB United Kingdom (GB) Massachusetts Institute of Technology (MIT) US United States (USA) (US) University of Nevada Las Vegas US United States (USA) (US)

How to cite

APA:

Ludlam, R.M., Jaodand, A.D., Garcia, J., Degenaar, N., Tomsick, J.A., Cackett, E.M.,... Chakrabarty, D. (2021). Simultaneous NICER and NuSTAR observations of the ultracompact x-ray binary 4u 1543-624. Astrophysical Journal, 911(2). https://dx.doi.org/10.3847/1538-4357/abedb0

MLA:

Ludlam, R. M., et al. "Simultaneous NICER and NuSTAR observations of the ultracompact x-ray binary 4u 1543-624." Astrophysical Journal 911.2 (2021).

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