First Look at the High-resolution X-Ray Spectra in the Highly Absorbed High-mass X-Ray Binary IGR J16318−4848 with Chandra

Pradhan P, Huenemoerder DP, Paul B, Amato R, Ballhausen R, Canizares C, Coley JB, Diez CM, Fürst F, Gandhi P, Grinberg V, Gunderson S, Ignace R, Kretschmar P, Lorenz M, Malacaria C, Manousakis A, Martínez-Núñez S, Pottschmidt K, Rodriguez J, Rothschild RE, Torrejón JM, Vander Meulen B, Wilms J (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Book Volume: 1004

Article Number: 215

Journal Issue: 2

DOI: 10.3847/1538-4357/ae5b71

Abstract

We present a comprehensive analysis of the X-ray spectrum of the highly obscured high-mass X-ray binary IGR J16318−4848 based on ∼250 ks Chandra/HETGS observations covering different orbital phases. We detected a strong narrow Fe Kα emission line and interpret our finding as the iron line originating in the stellar wind close to the compact object. We tentatively identify a Compton shoulder associated with the Fe Kα line. The ratio of the Compton-shoulder flux to that of the Fe Kα core exhibits orbital-phase variability, reaching a maximum of ∼10% around orbital phase ϕorb ≃ 0.33. In addition, we do not detect ionized lines, implying that the plasma in the system is predominantly cold. We preliminarily report that the Fe Kα line centroid exhibits an orbital modulation with an amplitude of 167 ± 32 km s⁻¹, adopting the best-known circular orbit in the source. This study presents the first detailed view of the high-resolution X-ray spectra of IGR J16318−4848 across different orbital phases, providing timely context for the newly taken XRISM observations of the source.

Authors with CRIS profile

Involved external institutions

Massachusetts Institute of Technology (MIT) United States (USA) (US) Howard University United States (USA) (US) European Space Astronomy Centre (ESAC) Spain (ES) University of Southampton United Kingdom (GB) European Space Research and Technology Centre (ESTEC, ESA) Netherlands (NL) Embry-Riddle Aeronautical University (ERAU) United States (USA) (US) Raman Research Institute (RRI) India (IN) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) Italy (IT) University of Maryland, College Park (UMD) United States (USA) (US) East Tennessee State University United States (USA) (US) University of Sharjah (UOS) / جامعة الشارقة United Arab Emirates (AE) Universidad de Cantabria (UC) Spain (ES) University of Maryland, Baltimore County (UMBC) United States (USA) (US) Université Paris-Saclay France (FR) University of California, San Diego (UC San Diego, UCSD) United States (USA) (US) University of Alicante / Universidad de Alicante / Universitat d'Alacant Spain (ES)

How to cite

APA:

Pradhan, P., Huenemoerder, D.P., Paul, B., Amato, R., Ballhausen, R., Canizares, C.,... Wilms, J. (2026). First Look at the High-resolution X-Ray Spectra in the Highly Absorbed High-mass X-Ray Binary IGR J16318−4848 with Chandra. Astrophysical Journal, 1004(2). https://doi.org/10.3847/1538-4357/ae5b71

MLA:

Pradhan, Pragati, et al. "First Look at the High-resolution X-Ray Spectra in the Highly Absorbed High-mass X-Ray Binary IGR J16318−4848 with Chandra." Astrophysical Journal 1004.2 (2026).

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