2018/01/22 by John A. Tomsick, Michael L. Parker, Javier A. Garcia +14 · 138 citations
Physics and Astronomy · #Accretion (finance) #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Binary number #Binary star #Cutoff #Electron density #RADIUS #Reflection (computer programming) #Spectral density #Spectral line #Stellar, planetary, and galactic studies #Thermal #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/aaaab1
published in The Astrophysical Journal 855(1), 3 (IOP Publishing) · 14 pages, accepted by ApJ
arxiv created 2018/01/22 · openalex created_date 2018/02/02 · openalex publication_date 2018/02/27 · arxiv updated 2018/03/14 · openalex updated_date 2026/08/06
Abstract Here we study a 1–200 keV energy spectrum of the black hole binary Cygnus X-1 taken with NuSTAR and Suzaku . This is the first report of a NuSTAR observation of Cyg X-1 in the intermediate state, and the observation was taken during the part of the binary orbit where absorption due to the companion’s stellar wind is minimal. The spectrum includes a multi-temperature thermal disk component, a cutoff power-law component, and relativistic and nonrelativistic reflection components. Our initial fits with publicly available constant density reflection models ( relxill and reflionx ) lead to extremely high iron abundances (>9.96 and times solar, respectively). Although supersolar iron abundances have been reported previously for Cyg X-1, our measurements are much higher and such variability is almost certainly unphysical. Using a new version of reflionx that we modified to make the electron density a free parameter, we obtain better fits to the spectrum even with solar iron abundances. We report on how the higher density ( cm −3 ) impacts other parameters such as the inner radius and inclination of the disk.