Abstract
We present the results of long-term high-dispersion spectral observations (R = 20000) of the Ae Herbig star HD 36112 in the regions of the Ha emission line and the NaI D resonance doublet lines. They show that parameters of the Ha emission line demonstrate complicated variability on several time scales: 1) variability from night to night caused by inhomogeneity of the circumstellar envelope; 2) variability on a time scale of about 1200d characterized by a variation of the equivalent width, intensity, and other emission parameters; 3) variability on a time scale of more than 4000d observed as a many-year trend in variations of parameters of the Ha emission line.
 We associate these results with variability of physical and kinematic conditions in the inner regions of the accretion disk and wind. The most probable mechanism of this variability is a process of planet formation in the circumstellar disk.
Highlights
The star HD 36112 (MWC 758) is attributed to a group of young hot intermediate-mass stars or the Ae/Be Herbig stars
Accretion of the circumstellar (CS) matter on the star is known to occur in its inner regions, whereas the processes of gas–wind outflows are observed at high latitudes
The Ae/Be Herbig stars are characterized by the presence in their spectra of CS emission lines, which are formed in the gaseous envelope, as well as by the IR excesses associated with circumstellar dust radiation
Summary
The star HD 36112 (MWC 758) is attributed to a group of young hot intermediate-mass stars or the Ae/Be Herbig stars. The Ae/Be Herbig stars are characterized by the presence in their spectra of CS emission lines, which are formed in the gaseous envelope, as well as by the IR excesses associated with circumstellar dust radiation. This is true with regard to HD 36112. A detailed analysis of fast spectral variability of HD 36112 was carried out in Pogodin (1995) and Beskrovnaya et al (1999) The results of these studies showed that the CS emission lines in a spectrum have a P Cyg-type profile, which is characteristic of outflowing gas. Since the modeling data show that the planet formation process (coupled with binarity) is able to not just change the structure of disks but produce a variation of the accretion rate on a time scale that is equal to the orbital period (see Demidova, 2016, 2009), we attempted to ascertain the observed signatures of such variations using the data of many-year spectral monitoring of HD 36112 conducted at the Crimean Astrophysical Observatory
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