Browsing by Author "Schlegel, Eric M."

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Characterizing the Advective Hot Flows of Nova-Like Cataclysmic Variables in the X-Rays: the Case of Bz Cam and V592 Cas
(Iop Publishing Ltd, 2022) Balman, Solen; Schlegel, Eric M.; Godon, Patrick
We present a joint spectral analysis of ROSAT PSPC, Swift X-ray Telescope, and Nuclear Spectroscopic Telescope Array Focal Plane Module A/B (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(2)(nu), 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 Ka 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 quasiperiodic oscillation at 1.4(-0.3)(+2.6) In general, we find that the two NLs portray spectral and noise characteristics as expected from advective hot accretion flows at low radiative efficiency.
X-Ray Spectroscopy of the Dwarf Nova Z Chamaeleontis in Quiescence and Outburst Using the Xmm-Newton Observatory
(Iop Publishing Ltd, 2024) Balman, Solen; Schlegel, Eric M.; Godon, Patrick; Drake, Jeremy J.
We present X-ray spectroscopy of the SU UMa-type dwarf nova Z Chamaeleontis using the European Photon Imaging Camera and reflection grating spectrometer (RGS) instruments on board the XMM-Newton observatory. The quiescent system can be modeled by collisional equilibrium (CIE) or nonequilibrium plasma models, yielding a kT of 8.2-13.0 keV at a luminosity of (5.0-6.0) x 10(30) erg s(-1). The spectra yield better chi(nu)2 using partially covering absorbers of cold and/or photoionized nature. The ionized absorber has an equivalent N-H = (3.4-5.9) x 10(22) cm(-2) and a log(xi) = 3.5-3.7 with a (50-60)% covering fraction when the VNEI model (XSPEC) is used. The line diagnosis in quiescence shows no resonance lines, with only the forbidden lines of Ne, Mg, and Si detected. The H-like C, O, Ne, and Mg are detected. The strongest line is O viii, with (2.7-4.6) x 10(-14) erg s(-1) cm(-2). The quiescent X-ray-emitting plasma is not collisional and not in ionization equilibrium, which is consistent with hot ADAF-like accretion flows. The line diagnosis in the outburst shows He-like O and Ne, with intercombination lines being the strongest, along with weaker resonance lines. This indicates the plasma is more collisional and denser, but not yet in CIE, revealing ionization timescales of (0.97-1.4) x 10(11) s cm(-3). The R ratios in the outburst yield electron densities of (7-90) x 10(11) cm(-3) and the G ratios yield electron temperatures of (2-3) x 10(6) K. The outburst luminosity is (1.4-2.5) x 10(30) erg s(-1). The flow is inhomogeneous in density. All detected lines are narrow, with widths limited by the resolution of RGS, yielding Keplerian rotational velocities <1000 km s(-1). This is too low for boundary layers, consistent with the nature of ADAF-like hot flows.