Probing the tidal disruption event iPTF16axa with CLOUDY and disc-wind models

Abstract

We present both a disc-wind model on the optical/UV emission continuum and CLOUDY modelling on the spectral lines of the tidal disruption event (TDE) iPTF16axa to understand the disc-wind emission and the properties of the atmosphere that impacts the line luminosity of the TDE. Assuming the optical/UV emission from the wind due to the disc super-Eddington phase, we use the steady structured disc-wind model with a spherical wind with constant velocity to fit the observations on multiple days. The extracted parameters are stellar-mass $M_{\star }=6.20\pm 1.19M_{\odot }$, disc radiative efficiency ${\log }_{10}(\eta )=-1.22\pm 1.327$, wind inner radius $r_l=(2.013\pm 0.551)\times 10^{14}\mathrm{cm}$ and velocity $v_w=18999.4\pm 1785.1\mathrm{km}{\mathrm{s}}^{-1}$. The photosphere temperature for wind emission is $\sim 2\times 10^4\mathrm{K}$ and the disc single blackbody temperature is $\sim 0.995\times 10^5\mathrm{K}$. We also perform CLOUDY modelling to explain the observed He and H line luminosities that estimate a wind inner radius $r_l=7.07\times 10^{14}\mathrm{cm}$ and velocity $v_w=1.3\times 10^4\mathrm{km}{\mathrm{s}}^{-1}$. The independent analyses of iPTF16axa using CLOUDY and disc-wind models show comparable results that agree with observations. The CLOUDY modelling finds that both the super solar abundance of He and a smaller He II line optical depth is responsible for the enhancement of He II line luminosity over the H$\alpha$ line luminosity. The super-solar abundance of He II agrees with a relatively large stellar mass and suggests that the disrupted star might have been a red giant.

12 pages, 5 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

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Cited by in corpus (1)

• Radiative hydrodynamical simulations of super-Eddington accretion flow in tidal disruption event: the accretion flow and wind