Research Information System
Astrophysical Journal, vol.1003, no.1, 2026 (SCI-Expanded, Scopus)
Nova-likes, such as BZ Cam, are high-state cataclysmic variables showing hard X-ray emission that can be characterized by advective hot flows in the inner accretion disk. We explore Chandra High Energy Transmission Grating observations of BZ Cam for detailed line diagnosis and ionization conditions in the X-ray regime. We mostly find H- and He-like emission lines of Mg, Si, S, and Fe. All He-like line components of forbidden, intercombination, and resonance lines are present. The R ratios of selected lines indicate plasma densities of a few ×1012−14 cm−3, and G ratios reveal temperatures of (3–6) × 106 K, where the Fe lines yield temperatures of (1–3) × 107 K. The H-to-He line ratios and the R and G ratios show that the plasma is in a nonequilibrium ionization condition, which is consistent with our previous X-ray results and the accretion flow in the X-ray region being an advection-dominated accretion flow-like (advective) hot flow. Simultaneous fits of the High Energy Grating (HEG) and Medium Energy Grating (MEG) spectra or the broadband joint spectra of ROSAT, Chandra zero order, and NuSTAR yield temperatures of 3.4–6.3 keV using a VNEI model of plasma emission (in XSPEC) or Bremsstrahlung emission. An additional power law is detected above the 98% CL in the broadband analysis. The orbital variations and the broadband spectra show dipping/veiling of the X-rays, and an additional warm absorber model with an ionization parameter log(ξ) = 2.7 is required at the 3σ level, along with the VNEI model, where the HEG and MEG simultaneous fits yield log(ξ) = 3.6.