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تسجيل مستخدم جديدSpectroscopic and photometric monitoring of a poorly known high-luminous OH/IR star: IRAS 18278+0931
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We present the time-dependent properties of a poorly known OH/IR star $-$ IRAS 18278+0931 (hereafter, IRAS 18+09) towards the Ophiuchus constellation. We have carried out long-term optical/near-infrared (NIR) photometric and spectroscopic observations to study the object. From optical $R$- and $I$-band light curves, the period of IRAS 18+09 is estimated to be 575 $pm$ 30 days and the variability amplitudes range from $Delta$R $sim$ 4.0 mag to $Delta$I $sim$ 3.5 mag. From the standard Period-Luminosity (PL) relations, the distance ($D$) to the object, 4.0 $pm$ 1.3 kpc, is estimated. Applying this distance in the radiative transfer model, the spectral energy distribution (SED) are constructed from multi-wavelength photometric and IRAS-LRS spectral data which provides the luminosity, optical depth, and gas mass-loss rate (MLR) of the object to be 9600 $pm$ 500 $L_{odot}$, 9.1 $pm$ 0.6 at 0.55 $mu$m and 1.0$times$10$^{-6}$ M$_odot$ yr$^{-1}$, respectively. The current mass of the object infers in the range 1.0 $-$ 1.5 $M_odot$ assuming solar metallicity. Notably, the temporal variation of atomic and molecular features (e.g., TiO, Na I, Ca I, CO, H$_2$O) over the pulsation cycle of the OH/IR star illustrates the sensitivity of the spectral features to the dynamical atmosphere as observed in pulsating AGB stars.
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