The Broadband Spectral Variability of Holmberg IX X-1

摘要: We present results from four new broadband X-ray observations of the extreme ultraluminous source Holmberg IX X-1 (L_X > 10^(40) erg s^(−1)), performed by Suzaku and NuSTAR in coordination. Combined with archival data, we now have this remarkable six separate epochs. Two these probe lower fluxes than seen previously, allowing us to extend our knowledge spectral variability exhibited. The spectra are well fit two thermal blackbody components that dominate emission below 10 keV, as a steep (Γ ~ 3.5) power-law tail dominates above ~15 keV. Remarkably, while 0.3–10.0 keV flux varies factor ~3 between all epochs, 15–40 only ~20%. Although is strongest ~1–10 band, both required vary when epochs considered. also revisit search for iron absorption features leveraging high-energy data improve sensitivity velocity outflows light ultra-fast outflow recently detected NGC 1313 X-1. Iron similar along line sight can be ruled out case. discuss context super-Eddington accretion models invoke funnel-like geometry inner flow, propose scenario which an almost face-on view funnel expands larger radii increasing flux, resulting degree geometrical collimation intermediate-temperature regions.