Modeling Emission Lines from Dwarf Novae in Quiescence

Ko, Yuan‐Kuen; Lee, Y. Paul; Schlegel, Eric M.; Kallman, T. R.

doi:10.1086/176736

Cited by 19 publications

(23 citation statements)

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“…The Gaussian fits to the emission lines showed no trend in the line width (Gaussian FWHM) with continuum or a Line flux and radial line emissivity predictions from the models of Ko et al (1996), labeled here for clarity as K96. Cases 8-10 invoke a two-component model for the photoionizing continuum.…”

Section: Variability In the Emission Lines And The Continuummentioning

confidence: 96%

“…For case 10, the soft component is a 5 ; 10 5 blackbody with L X ¼ 10 32 ergs s À1 . The UV line flux ratios have been taken from Table 7 of Ko et al (1996), while the radial power-law emissivity indices have been derived from the UV line fluxes in Table 4 of Ko et al (1996). b Power-law indices for models marked ¼ 0 have been derived from the observations under the assumption that the lines are optically thin.…”

Section: Variability In the Emission Lines And The Continuummentioning

confidence: 99%

“…In addition, they find that observed hard X-ray luminosities in DNe are too low to generate observed line fluxes using their model, and they postulate the existence of an additional EUV/soft X-ray component with L X k 10 32 ergs s À1 . In Table 4 we compare our observed emission-line flux ratios and radial surface brightness indices with those of the twocomponent models of Ko et al (1996). In their two-component models, the hard X-ray component is fixed while the luminosity and shape of the soft X-ray/EUV component are varied.…”

Section: The Uv Line Emissionmentioning

confidence: 99%

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Far‐Ultraviolet Spectroscopy of the Dwarf Novae SS Cygni and WX Hydri in Quiescence

Long

Froning

Knigge

et al. 2005

ApJ

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We present time-resolved FUV spectra of the dwarf novae SS Cyg and WX Hyi in quiescence from observations using the Hopkins Ultraviolet Telescope on the Astro-1 and Astro-2 space shuttle missions and the Goddard High Resolution Spectrograph on the Hubble Space Telescope. Both dwarf novae are characterized by blue continua that extend to the Lyman limit punctuated by broad emission lines including transitions of O vi, N v, Si iv, and C iv. The continuum of WX Hyi can be fitted with a white dwarf model with physically reasonable model parameters, but neither system actually shows unambiguous signatures of white dwarf emission. The shape and flux of the spectrum of SS Cyg cannot be self-consistently reconciled with a white dwarf providing all of the FUV continuum flux. Combination white dwarf /disk or white dwarf /optically thin plasma models improve the fit but still do not give physically reasonable model parameters for a quiescent dwarf nova. Assuming that the UV emission lines arise from the disk, the line shapes indicate that surface fluxes fall roughly as R À2 in both systems. Fits to the double-peaked line profiles in SS Cyg indicate that the FUV line-forming region is concentrated closer to the white dwarf than that of the optical lines and provide no evidence of a hole in the inner disk. Although the flux from SS Cyg was relatively constant during all of our observations, WX Hyi showed significant variability during the GHRS observations. In WX Hyi, the line and continuum fluxes are (with the exception of He ii) highly correlated, indicating a link between the formation mechanisms of the line and continuum regions.

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Section: Variability In the Emission Lines And The Continuummentioning

confidence: 96%

Section: Variability In the Emission Lines And The Continuummentioning

confidence: 99%

Section: The Uv Line Emissionmentioning

confidence: 99%

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Far‐Ultraviolet Spectroscopy of the Dwarf Novae SS Cygni and WX Hydri in Quiescence

Long

Froning

Knigge

et al. 2005

ApJ

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“…Unfortunately, there are few models for a hot component in a quiescent disk, the basic problem being of course that a hot portion of the disk should trigger the disk instability. One interesting possibility, recently investigated by Ko et al (1996) as an extension of their studies of disks in X-ray binaries, is that X-ray and EUV radiation from the vicinity of the WD photoionizes and heats a surface layer on the disk to produce a hot corona. [As discussed by Meyer & Meyer-Hofmeister (1990), X-ray illumination of a disk does not induce, but tends to stabilize against disk instabilities.]…”

Section: Dwarf Novae In Quiescencementioning

confidence: 99%

Far Ultraviolet Observations of Dwarf Novae made with the Hopkins Ultraviolet Telescope

Long

1996

International Astronomical Union Colloquium

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Abstract.Observations with the Hopkins Ultraviolet Telescope on the Astro-1 and Astro-2 space shuttle missions have provided the first set of moderate (3 A) resolution far ultraviolet (FUV) spectra of dwarf novae to include the wavelength range between Lya and the Lyman limit. Important lines which are detected in the HUT spectra of dwarf novae in this wavelength range include S vi AA933,945, C in A977, O vi AA1032,1038, P v AA1118,1128 and C m A1176, as well as the higher order Lyman lines. The observations confirm earlier IUE observations that two dwarf novae -U Gem and VW Hyi -have quiescent FUV spectra dominated by the white dwarf, but suggest that the quiescent FUV emission from three other dwarf novae -SS Cyg, WX Hyi and YZ Cnc -are dominated by emission from a hot portion of the disk or a disk corona. The spectra obtained of the dwarf novae Z Cam and EM Cyg in outburst and also of the nova-like variable IX Vel can be modeled reasonably successfully in terms of steady state disks constructed by adding appropriately-weighted stellar model spectra.

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“…Absorption lines are obtained from optically thick disk simulations under LTE while NLTE effects must be considered to simulate emission lines. Ko et al (1996) presented a model where the accretion disk vertical structure and NLTE effects are considered, where a chromosphere is superposed to a standard model disk. A selfconsistent model for accretion disk extended atmosphere is still an open issue.…”

Section: Introductionmentioning

confidence: 99%

Tomographic Simulations of Accretion Disks in Cataclysmic Variables – Flickering and Wind

Ribeiro

Diaz

2006

Astrophys Space Sci

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Both continuum and emission line flickering are phenomena directly associated with the mass accretion process. In this work we simulate accretion disk Doppler maps including the effects of winds and flickering flares. Synthetic flickering Doppler maps are calculated and the effect of the flickering parameters on the maps is explored. Jets and winds occur in many astrophysical objects where accretion disks are present. Jets are generally absent among the cataclysmic variables (CVs), but there is evidence of mass loss by wind in many objects. CVs are ideal objects to study accretion disks and consequently to study the wind associated with these disks. We also present simulations of accretion disks including the presence of a wind with orbital phase resolution. Synthetic Hα line profiles in the optical region are obtained and their corresponding Doppler maps are calculated. The effect of the wind simulation parameters on the wind line profiles is also explored. From this study we verified that optically thick lines and/or emission by diffuse material into the primary Roche lobe are necessary to generate single peaked line profiles, often seen in CVs. The future accounting of these effects is suggested for interpreting Doppler tomography reconstructions.

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Modeling Emission Lines from Dwarf Novae in Quiescence

Cited by 19 publications

References 0 publications

Far‐Ultraviolet Spectroscopy of the Dwarf Novae SS Cygni and WX Hydri in Quiescence

Far‐Ultraviolet Spectroscopy of the Dwarf Novae SS Cygni and WX Hydri in Quiescence

Far Ultraviolet Observations of Dwarf Novae made with the Hopkins Ultraviolet Telescope

Tomographic Simulations of Accretion Disks in Cataclysmic Variables – Flickering and Wind

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