An XMM-Newton and NuSTAR Study of IGR J18214-1318: A Non-pulsating High-mass X-Ray Binary with a Neutron Star

Journal Article · Sat May 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA6FF4· OSTI ID:22872697

Fornasini, Francesca M. ^[1]; Tomsick, John A.; Krivonos, Roman A. ^[2]; Bachetti, Matteo ^[3]; Fürst, Felix ^[4]; Natalucci, Lorenzo ^[5]; Pottschmidt, Katja ^[6]; Wilms, Jörn ^[7]

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1. Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720 (United States)
2. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 (United States)
3. INAF/Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047 Selargius (Italy)
4. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
5. Istituto di Astrofisica e Planetologia Spaziali, INAF, Via Fosso del Cavaliere 100, I-00133 Roma (Italy)
6. Department of Physics and Center for Space Science and Technology, University of Maryland Baltimore County, Baltimore, MD 21250 (United States)
7. Dr. Karl-Remeis-Sternwarte and ECAP, Sternwartstr. 7, D-96049 Bamberg (Germany)

IGR J18214-1318, a Galactic source discovered by the International Gamma-Ray Astrophysics Laboratory, is a high-mass X-ray binary (HMXB) with a supergiant O-type stellar donor. We report on the XMM-Newton and NuSTAR observations that were undertaken to determine the nature of the compact object in this system. This source exhibits high levels of aperiodic variability, but no periodic pulsations are detected with a 90% confidence upper limit of 2% fractional rms between 0.00003–88 Hz, a frequency range that includes the typical pulse periods of neutron stars (NSs) in HMXBs (0.1–10{sup 3} s). Although the lack of pulsations prevents us from definitively identifying the compact object in IGR J18214-1318, the presence of an exponential cutoff with e-folding energy ≲30 keV in its 0.3–79 keV spectrum strongly suggests that the compact object is an NS. The X-ray spectrum also shows a Fe Kα emission line and a soft excess, which can be accounted for by either a partial-covering absorber with N{sub H}≈10{sup 23} cm{sup −2}, which could be due to the inhomogeneous supergiant wind, or a blackbody component with kT=1.74{sub −0.05}{sup +0.04} keV and R{sub BB}≈0.3 km, which may originate from NS hot spots. Although neither explanation for the soft excess can be excluded, the former is more consistent with the properties observed in other supergiant HMXBs. We compare IGR J18214-1318 to other HMXBs that lack pulsations or have long pulsation periods beyond the range covered by our observations.

• OSTI ID: 22872697
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 841; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
BLACK HOLES
COMPARATIVE EVALUATIONS
EMISSION
GAMMA RADIATION
KEV RANGE
MASS
NEUTRON STARS
PERIODICITY
PULSATIONS
STELLAR WINDS
X-RAY SPECTRA