New luminous blue variable candidates in the NGC 247 galaxy. Issue 4 (26th August 2020)

• Record Type: Journal Article
• Authors: Solovyeva, Y; Vinokurov, A; Sarkisyan, A; Atapin, K; Fabrika, S; Valeev, A F; Kniazev, A; Sholukhova, O; Maslennikova, O
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 4(2020)
• Page Start: 4834
• Page End: 4842
• Publication Date: 2020-08-26
• Subjects: stars: emission-line, Be -- stars: massive -- stars: variables: S Doradus -- galaxies: individual: NGC 247; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa2117
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We search for luminous blue variable (LBV) stars in galaxies outside the Local Group. Here we present a study of two bright Hα sources in the NGC 247 galaxy. Object j004703.27–204708.4 ( MV = −9.08 ± 0.15 mag) 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 Δ B = 0.74 ± 0.09 mag and Δ V = 0.88 ± 0.09 mag, which makes it a reliable LBV candidate. The star j004702.18–204739.93 ( MV = −9.66 ± 0.23 mag) 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 did not reveal significant variations in brightness (Δ V = 0.29 ± 0.09 mag). 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 correspond to bolometric luminosities $\log (L_\text{bol}/{\rm L}_{\odot })=6.11^{+0.20}_{-0.16}$ 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 a B[e]-supergiant.