The incidence of LBV variability in the LMC

Abstract

Luminous blue variables (LBVs) exhibit unique variability features, characterized by episodic outbursts ($>$1 mag) accompanied by spectroscopic changes (S Dor variables). It is debated if all massive stars undergo an LBV-like phase during their evolution, or instead LBVs are exotic phenomena. We aim to quantify the incidence of LBV-like variability in the blue supergiant (BSgs) population of the Large Magellanic Cloud (LMC) using the OGLE survey. Here, we extend previous work in the Small Magellanic Cloud to the LMC, where we examine the light curves of 87 B Supergiants (BSgs) (out of 254 known BSgs) spanning timescales of twenty years, and 37 objects across a three year timescale for aperiodic variations resembling known S Dor variables. One blue supergiant, [ST92] 4-13 shows S Dor type photometric variations. New spectra of this object reveals a potential change in spectral type compared to the literature classification. However, based on its spectral characteristics and low luminosity and mass, we do not currently classify it as an LBV. Our study highlights the need to classify bona fide LBVs as stars undergoing both photometric and spectroscopic variations. Based on currently known stellar population of S Dor variables in the LMC, the lifetime of the S Dor phase is at most $\sim$10${}^3$ yrs, in agreement with our duty cycle study based on OGLE data in the SMC. This is orders of magnitude shorter than assumed in literature. Our discovery of LBV-like variability at low luminosities may suggest that S Dor variations could arise from Eddington limit related physics over a wide range of stellar masses, rather than being linked to a unique evolutionary stage.

Accepted for publication in A&A; 11 pages, 8 figures. Comments/suggestions welcome

References in corpus (18)

• Gaia Data Release 3: Summary of the content and survey properties
• A distance to the Large Magellanic Cloud that is precise to one per cent
• Spitzer SAGE Infrared Photometry of Massive Stars in the Large Magellanic Cloud
• The VLT-FLAMES survey of massive stars: Evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds
• A Survey of Local Group Galaxies Currently Forming Stars: III. A Search for Luminous Blue Variables and Other H-alpha Emission-Lined Stars
• Luminous Blue Variables as the progenitors of supernovae with quasi-periodic radio modulations
• Luminous Blue Variables and superluminous supernovae from binary mergers
• Gaia Data Release 3. Summary of the variability processing and analysis
• SN 2005 gj: Evidence for LBV supernovae progenitors?
• Comparative performance of selected variability detection techniques in photometric time series
• Gaia Data Release 3: Gaia scan-angle dependent signals and spurious periods
• Simulating the formation of $\eta$ Carinae's surrounding nebula through unstable triple evolution and stellar merger-induced eruption
• Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, and the B[e] Supergiants; How to Tell Them Apart
• Wind-envelope interaction as the origin of the slow cyclic brightness variations of luminous blue variables
• Luminous and Variable Stars in M31 and M33 V. The Upper HR Diagram
• Binarity at Low Metallicity (BLOeM) -- Multiplicity properties of Oe and Be stars
• Galactic Twins of the Nebula Around SN 1987A: Hints that LBVs may be supernova progenitors
• A search for Be stars in multiple systems within the solar neighborhood