The variability of the spectrum of the optical component of the IR-source
IRAS01005+7910 was discovered for the first time in the BTA spectra .
Long-term monitoring of the object was carried out during 2002-2013 with
a high spectral resolution (R=60000). The following fundamental parameters
were determined: luminosity log L/L☼=3.6 and effective temperature
Teff=21500K of the central star, and the chemical composition
([Fe/H]=-0.3, C/O>1) of its atmosphere. The spectral features include
absorptions that form in near-photospheric layers, narrow envelope
emissions, and emission-absorption profiles that form in
photosphere-to-envelope transition layers (the wind). The presence of
forbidden emissions [NII] and [SII] in the spectrum indicates the onset
of the ionization of the circumstellar envelope and the nearing planetary
nebula stage. We show that the deviations of the wind from spherical
symmetry are small, which is in agreement with the shape of the
circumstellar envelope according to HST images (Fig.1). Figs. 2 and 3
show examples of variations of the form and position of the profiles.
The systemic velocity of the source, Vsys=-50.5 km/s, was determined
for the first time from the positions of symmetric and stable profiles
of forbidden emissions. The complex pattern of velocity-field variations
(see example in Fig.4) is determined by pulsations, hidden binarity of
the star, and variations of the absorption components of the profiles
due to variations of the wind-base geometry and kinematics. The spectrum
of the object is a unique natural laboratory for studying the physical
and kinematic features of the atmosphere, expanding envelope, and
intermediate structures. The relatively low wind velocity (27-74 km/s,
based on different observations) and the high intensity of the long
wavelength emission (up to 7 times higher than the continuum level, Fig.3)
are typical of hypergiants rather than supergiants. IRAS01005+7910 is an
example of a low-mass post-AGB star masquerading as a massive hypergiant.
Contact - Klochkova V.G.
1. V.G.Klochkova, M.V.Yushkin, A.S.Miroshnichenko, V.E.Panchuk,
K.Bjorkman. Discovery of spectral variation in the optical counterpart
of IRAS01005+7910. Astron.&Astrophys., 392, 143, 2002.
2. V.G.Klochkova, E.L.Chentsov, V.E.Panchuk, E.G.Sendzikas, M.V.Yushkin.
Spectral variability of the IR-source IRAS01005+7910 optical component.
Astrophys.Bull., 69, 439, 2014.
Images of IRAS01005+7910 obtained in different filters with the Hubble
Variations of the profiles of SiII 6347 Å, 4128+4130 Å
in the spectrum of IRAS01005+7910. Dashed line - envelope curve of all
the SiII 5979 Å profiles
Variations of Hα profiles in the spectra of IRAS01005+7910
(thin curve - 9.03.2004, thick curve - 18.01.2005). Dashed curve - envelope
emissions. Vertical dashed line - velocity based on forbidden emissions
Vr(r) dependence in the spectrum of IRAS01005+7910 from 29.05.2013.
Dots - forbidden emissions (r>1) and HeI and ion absorptions (r<1).
Open circles - emission (Vr <-60 km/s) and absorption (Vr > -40 km/s)
components of the FeIII line profiles