Characterizing the Advective Hot Flows of Nova-Like Cataclysmic Variables in the X-rays: The case of BZ Cam and V592 Cas

Abstract

We present a joint spectral analysis of ROSAT PSPC, Swift XRT, and NuSTAR FPMA/B data of the nova-like (NL) cataclysmic variables (CVs), BZ Cam and V592 Cas in the 0.1-78.0 keV band. Plasma models of collisional equilibrium fail to model the 6.0-7.0 iron line complex and continuum with ${\chi }_{\nu }^2$ larger than 2.0. Our results show nonequilibrium ionization (NEI) conditions in the X-ray plasma with temperatures of 8.2-9.4 keV and 10.0-12.9 keV for BZ Cam and V592 Cas, respectively. The centroids of He-like and H-like iron ionization lines are not at their equilibrium values as expected from NEI conditions. We find power law spectral components that reveal the existence of scattering and Comptonization with a photon index of 1.50-1.87. We detect a P Cygni profile in the H-like iron line of BZ Cam translating to outflows of 4500-8700 km s${}^{-1}$ consistent with the fast winds in the optical and UV. This is the first time such a fast collimated outflow is detected in the X-rays from an accreting CV. An Iron K$\alpha$ line around 6.2-6.5 keV is found revealing the existence of reflection effects in both sources. We study the broadband noise and find that the optically thick disk truncates in BZ Cam and V592 Cas consistent with transition to an advective hot flow structure. V592 Cas also exhibits a quasi-periodic oscillation at 1.4${}_{-0.3}^{+2.6}$ mHz. In general, we find that the two NLs portray spectral and noise characteristics as expected from advective hot accretion flows at low radiative efficiency.

19 pages, 2 Tables, 5 Figures (13 individual); Astrophysical Journal in Press, subject to minor changes during the production process

References in corpus (13)

• Modelling the behaviour of accretion flows in X-ray binaries
• Advection-Dominated Accretion and the Black Hole Event Horizon
• Black hole-like hysteresis and accretion states in neutron star low mass X-ray binaries
• The jet-powered optical nebula of Cygnus X-1
• Accretion Flows in Nonmagnetic White Dwarf Binaries as Observed in X-rays
• Multi-Wavelength Coverage of State Transitions in the New Black Hole X-Ray Binary Swift J1910.2-0546
• X-ray observations of VY Scl type nova-like binaries in the high and low state
• The luminosity evolution of nova shells -- I. A new analysis of old data
• A Systematic X-ray Study of the Dwarf Novae Observed with Suzaku
• An Improved Model for the Spectra of Disks of Nova-like Variables
• Observations of V592 Cas - An Outflow at Optical Wavelengths
• A Search for the modern counterparts of the Far Eastern guest stars 369 CE, 386 CE, and 393 CE
• Peculiarities of the Accretion Flow in the System HL CMa

Cited by in corpus (3)

• Broad Observational Perspectives Achieved by the Accreting White Dwarf Sciences in the XMM-Newton and Chandra Eras
• XMM-Newton observation of V1504 Cyg as a probe for the existence of an evaporated corona
• Identification of Z Cam's Historical Counterpart: The Quest for an Ancient Nova