New luminous blue variable candidates in the NGC 247 galaxy

Abstract

We search for LBV stars in galaxies outside the Local Group. Here we present a study of two bright $H\alpha$ sources in the NGC 247 galaxy. Object j004703.27-204708.4 ($M_V=-9.08\pm 0.15^m$) shows the spectral lines typical for well-studied LBV stars: broad and bright emission lines of hydrogen and helium He I with P Cyg profiles, emission lines of iron Fe II, silicon Si II, nitrogen N II and carbon C II, forbidden iron [Fe II] and nitrogen [N II] lines. The variability of the object is $\Delta B=0.74\pm 0.09^m$ and $\Delta V=0.88\pm 0.09^m$, which makes it reliable LBV candidate. The star j004702.18-204739.93 ($M_V=-9.66\pm 0.23^m$) shows many emission lines of iron Fe II, forbidden iron lines [Fe II], bright hydrogen lines with broad wings, and also forbidden lines of oxygen [O I] and calcium [Ca II] formed in the circumstellar matter. The study of the light curve of this star also did not reveal significant variations in brightness ($\Delta V=0.29\pm 0.09^m$). We obtained estimates of interstellar absorption, the photosphere temperature, as well as bolometric magnitudes $M_{\text{bol}}=-10.5_{-0.4}^{+0.5}$ and $M_{\text{bol}}=-10.8_{-0.6}^{+0.5}$, which corresponds to bolometric luminosities $\log (L_{\text{bol}}/L_{\odot })=6.11_{-0.16}^{+0.20}$ and $6.24_{-0.25}^{+0.20}$ for j004703.27-204708.4 and j004702.18-204739.93 respectively. Thus, the object j004703.27-204708.4 remains a reliable LBV candidate, while the object j004702.18-204739.93 can be classified as B[e]-supergiant.

Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal 2020 July 15

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