2017/09/05 by Renee M. Ludlam, R. M. Ludlam, Jon M. Miller +11 · 2 citations
Physics and Astronomy · #Accretion (finance) #Accretion disc #Astrophysical Phenomena and Observations #Binary star #Eddington luminosity #Gamma-ray bursts and supernovae #Magnetic field #Magnetosphere #Neutron star #Pulsars and Gravitational Waves Research #RADIUS #X-ray binary #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/aa8b1b
Accepted for publication in ApJ, 7 pages, 2 Tables, 5 Figures
arxiv created 2017/09/05 · openalex created_date 2017/09/15 · openalex publication_date 2017/10/01 · arxiv updated 2017/10/11 · openalex updated_date 2026/08/05
Abstract We perform a reflection study on a new observation of the neutron star (NS) low-mass X-ray binary Aquila X-1 taken with NuSTAR during the 2016 August outburst and compare with the 2014 July outburst. The source was captured at ∼32% L Edd , which is over four times more luminous than the previous observation during the 2014 outburst. Both observations exhibit a broadened Fe line profile. Through reflection modeling, we determine that the inner disk is truncated (where R g = GM / c 2 ) and (errors quoted at the 90% confidence level). Fiducial NS parameters ( M NS = 1.4 M ⊙ , R NS = 10 km) give a stellar radius of R NS = 4.85 R g ; our measurements rule out a disk extending to that radius at more than the 6 σ level of confidence. We are able to place an upper limit on the magnetic field strength of B ≤ 3.0–4.5 × 10 9 G at the magnetic poles, assuming that the disk is truncated at the magnetospheric radius in each case. This is consistent with previous estimates of the magnetic field strength for Aquila X-1. However, if the magnetosphere is not responsible for truncating the disk prior to the NS surface, we estimate a boundary layer with a maximum extent of and . Additionally, we compare the magnetic field strength inferred from the Fe line profile of Aquila X-1 and other NS low-mass X-ray binaries to known accreting millisecond X-ray pulsars.