Optical Spectrum of Distant OH/IR Star V1648 Aql (IRAS 19386+0155)

Аннотация

We present an optical spectrum of the star V1648 Aql (IRAS19386+0155) obtained at the 6-m SAO RAS telescope with a spectral resolution of R ≥ 60 000. Heliocentric radial velocity was measured from numerous metal absorptions is V_r = 10.18 ± 0.05 km s^-1 (V_LSR = 18.1 km s^-1). We determined the atmospheric, circumstellar, and interstellar components in the profile of the Na I D lines at V_r = 9.2, -3.4, and -12.8 km s^-1 respectively. The averaged over 20 identified DIBs velocity V_r = -12.5 ± 0.2 km s^-1 coincides with the interstellar Na I component. Weak emissions with an intensity of about 10% of the local continuum level were detected in the spectrum; they are identified as low-excitation metal lines. Their central position, V_r = 8.44 ± 0.28 km s^-1, points to the presence of a weak velocity gradient in the upper layers of the stellar atmosphere. Based on the spectroscopic data and taking into account the interstellar and circumstellar reddening, we estimated the star’s luminosity M_V ≈ -5^m and also obtained the lower estimate of distance d ≥ 1.8 kpc. Using the model atmosphere method, we determined the fundamental parameters and chemical abundances in the atmosphere confirming the status of a post-AGB star for V1648 Aql.