Chandra HETG line spectroscopy of the Non-magnetic Cataclysmic Variable SS Cyg

Abstract

We present {\it Chandra} HETG observations of SS Cygni in quiescence and outburst. The spectra are characterized by He-like and H-like Ka emission lines from O to Fe, as well as L-shell emission lines from Fe. In quiescence, the spectra are dominated by the H-like Ka lines, whereas in outburst the He-like lines are as intense as the H-like lines. In outburst, the H-like Ka lines from O to Si are broad, with widths of 4--14 eV in Gaussian $\sigma$ (1800--2300$\mathrm{km}{\mathrm{s}}^{-1}$). The large line widths, together with line profiles, indicate that the line-emitting plasma is associated with the Keplerian disk and still retains the azimuthal bulk motion. In quiescence, the emission lines are narrower, with a Gaussian $\sigma$ of 1--3 eV (420--620$\mathrm{km}{\mathrm{s}}^{-1}$). A slightly larger velocity for lighter elements suggests that the lines in quiescence are emitted from an ionizing plasma at the entrance of the boundary layer, where the bulk motion of the optically thick accretion disk is converted into heat due to friction. Using the line intensity ratio of He-like and H-like Ka lines for each element, we have also investigated the temperature distribution in the boundary layer both in quiescence and outburst. The distribution of SS Cyg is found to be consistent with other dwarf novae investigated systematically with {\it ASCA} data.

arXiv comment23 pages, 10 figures, accepted for publication in the Astrophysical Journal

References in corpus (9)

• The disc instability model of dwarf-novae and low-mass X-ray binary transients
• The Chandra High Energy Transmission Grating: Design, Fabrication, Ground Calibration and Five Years in Flight
• The complete set of ASCA X-ray observations of non-magnetic cataclysmic variables
• Two Types of X-ray Spectra in Cataclysmic Variables
• The X-ray and extreme-ultraviolet flux evolution of SS Cygni throughout outburst
• The X-ray Spectrum of the Dwarf Nova SS Cyg in quiescence and outburst
• Spectroscopic observations of the candidate sgB[e]/X-ray binary CI Cam
• Study of Fe K-alpha lines in Non-magnetic Cataclysmic Variables using Chandra HEG data
• Chandra Low Energy Transmission Grating Spectrum of SS Cygni in Outburst

Cited by in corpus (5)

• SWIFT XRT Observations of the Nova-like Cataclysmic Variables MV Lyr, BZ Cam and V592 Cas
• Accretion Flows in Nonmagnetic White Dwarf Binaries as Observed in X-rays
• X-ray spectroscopy in the microcalorimeter era 4: Optical depth effects on the soft X-rays studied with CLOUDY
• Pre-outburst $Chandra$ Observations of the Recurrent Nova T Pyxidis
• X-ray properties of dwarf nova EY Cyg and the companion star using an XMM-Newton observation