Modeling of the spectral energy distribution of the cataclysmic variable TT Ari and evaluation of the system parameters

TL;DR

This study models the spectral energy distribution of TT Ari using a steady-state accretion disc, deriving system parameters and fitting observed spectra to better understand the system's physical characteristics.

Contribution

It provides new estimates of system parameters of TT Ari, including white dwarf mass, inclination, and accretion rate, based on combined spectral modeling and observational data.

Findings

Derived white dwarf mass range: 0.57-1.2 M_sun

Estimated system inclination: 17-22.5 degrees

Fitted spectral model with additional thermal component

Abstract

The spectral energy distribution (SED) of the TT Ari system, which is well known from published IUE and optical photometric observations, was modeled by a steady-state accretion \alpha-disc around a white dwarf. Parameters of the system were derived from time-resolved optical spectral observations in the bright state that we obtained in Sep. 1998. The radial velocity semi-amplitude of the white dwarf (33.8 +/- 2.5 km/s) and corresponding mass function (f(M) = 5.5 +/- 1.2 *10^{-4}~ M_sun) were derived from the motion of the emission components of Balmer lines. The mass ratio q (\approx 0.315) was evaluated from the fractional period excess of the superhump period over the orbital period \epsilon (\approx 0.085), and a secondary mass range (0.18 - 0.38 M_sun) was estimated from the orbital period. Therefore, the white dwarf mass range is 0.57 - 1.2 M_sun and the inclination angle of the system to the line of sight is 17 - 22.5 degrees. The adopted distance to the system is 335 +/- 50 pc. To fit the observed SED it is necessary to add a thermal spectrum with T \approx 11600 K and luminosity \approx 0.4 L_disk to the accretion disc spectrum. This combined spectrum successfully describes the observed Balmer lines absorption components. Formally the best fit of the HeI 4471 line gives minimum masses of the components (M_RD = 0.18 M_sun and M_WD = 0.57 M_sun), with the corresponding inclination angle i = 22.1 deg and mass-accretion rate \dot M = 2.6 * 10^{17} g/s.