2017/08/31 by Benjamin M. Coughenour, Edward M. Cackett, Jon M. Miller +1 · 28 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Binary number #Emission spectrum #Gamma-ray bursts and supernovae #Line (geometry) #Neutron star #RADIUS #Reflection (computer programming) #Spectral line #TRACE (psycholinguistics) #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/aae098
published in The Astrophysical Journal 867(1), 64 (IOP Publishing) · 12 pages, 7 figures, accepted by ApJ
openalex created_date 2017/08/17 · arxiv created 2018/09/11 · openalex publication_date 2018/10/31 · arxiv updated 2018/11/07 · openalex updated_date 2026/08/05
Abstract Although the most luminous class of neutron star (NS) low-mass X-ray binaries, known as Z sources, have been well studied, their behavior is not fully understood. In particular, what causes these sources to trace out the characteristic Z-shaped pattern on color–color or hardness–intensity diagrams (HIDs) is not well known. By studying the physical properties of the different spectral states of these sources, we may better understand such variability. With that goal in mind, we present a recent NuSTAR observation of the Z source GX 349+2, which spans approximately 2 days and covers all its spectral states. By creating an HID we were able to extract five spectra and trace the change in spectral parameters throughout the Z-track. GX 349+2 shows a strong, broad Fe K α line in all states, regardless of the continuum model used. Through modeling of the reflection spectrum and Fe K α line we find that in most states the inner disk radius is consistent with remaining unchanged at an average radius of 17.5 R g or 36.4 km for a canonical 1.4 M ⊙ NS. During the brightest flaring branch, however, the inner disk radius from reflection is not well constrained.