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Register a new userNew luminous blue variable candidates in the NGC 247 galaxy
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Y. Solovyeva
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We search for LBV stars in galaxies outside the Local Group. Here we present a study of two bright $Halpha$ 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 $Delta B = 0.74pm0.09^m$ and $Delta V = 0.88pm0.09^m$, 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 ($Delta V = 0.29pm0.09^m$). We obtained estimates of interstellar absorption, the photosphere temperature, as well as bolometric magnitudes $M_text{bol}=-10.5^{+0.5}_{-0.4}$ and $M_text{bol}=-10.8^{+0.5}_{-0.6}$, which corresponds to bolometric luminosities $log(L_text{bol}/L_{odot})=6.11^{+0.20}_{-0.16}$ and $6.24^{+0.20}_{-0.25}$ 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.
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We have found three new LBV candidates in the star-forming galaxy NGC 4736. They show typical well-known LBV spectra, broad and strong hydrogen lines, He I lines, many Fe II lines, and forbidden [Fe II] and [Fe III]. Using archival Hubble Space Telescope and ground-based telescope data, we have estimated the bolometric magnitudes of these objects from -8.4 to -11.5, temperatures, and reddening. Source NGC 4736_1 (Mv = -10.2 +/- 0.1 mag) demonstrated variability between 2005 and 2018 as Delta V = 1.1 mag and Delta B = 0.82 mag, the object belongs to LBV stars. NGC 4736_2 (Mv < -8.6 mag) shows P Cyg profiles and its spectrum has changed from 2015 to 2018. The brightness variability of NGC 4736_2 is Delta V = 0.5 mag and Delta B = 0.4 mag. In NGC 4736_3 (Mv = -8.2 +/- 0.2 mag), we found strong nebular lines, broad wings of hydrogen; the brightness variation is only 0.2 mag. Therefore, the last two objects may reside to LBV candidates.
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