Optical spectroscopy of the blue supergiant Sk-69 279 and its circumstellar shell with SALT

Abstract

We report the results of optical spectroscopy of the blue supergiant Sk-69 279 and its circular shell in the Large Magellanic Cloud (LMC) with the Southern African Large Telescope (SALT). We classify Sk-69 279 as an O9.2 Iaf star and analyse its spectrum by using the stellar atmosphere code CMFGEN, obtaining a stellar temperature of \approx 30 kK, a luminosity of log(L_*/Lsun)=5.54, a mass-loss rate of log(\dot{M}/(Msun/yr))=-5.26, and a wind velocity of 800 km/s. We found also that Sk-69 279 possesses an extended atmosphere with an effective temperature of \approx 24 kK and that its surface helium and nitrogen abundances are enhanced, respectively, by factors of \approx 2 and 20--30. This suggests that either Sk-69 279 was initially a (single) fast-rotating (\ga 400 km/s) star, which only recently evolved off the main sequence, or that it is a product of close binary evolution. The long-slit spectroscopy of the shell around Sk-69 279 revealed that its nitrogen abundance is enhanced by the same factor as the stellar atmosphere, which implies that the shell is composed mostly of the CNO processed material lost by the star. Our findings support previous propositions that some massive stars can produce compact circumstellar shells and, presumably, appear as luminous blue variables while they are still on the main sequence or have only recently left it.

arXiv comment15 pages, 12 figures, accepted for publication in MNRAS

References in corpus (52)

• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• Binary interaction dominates the evolution of massive stars
• A new calibration of stellar parameters of Galactic O stars
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• Spitzer Survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (SAGE) I: Overview and Initial Results
• The VLT-FLAMES Tarantula Survey VIII. Multiplicity properties of the O-type star population
• The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars
• Presupernova Evolution of Rotating Massive Stars II: -- Evolution of the Surface Properties
• The Magellanic Clouds Photometric Survey: The Large Magellanic Cloud Stellar Catalog and Extinction Map
• The incidence of stellar mergers and mass gainers among massive stars
• Physical Parameters and Wind Properties of Galactic Early B Supergiants
• UBVJHK synthetic photometry of Galactic O stars
• The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars
• Bright OB stars in the Galaxy - III. Constraints on the radial stratification of the clumping factor in hot star winds from a combined Halpha, IR and radio analysis
• Spitzer SAGE Infrared Photometry of Massive Stars in the Large Magellanic Cloud
• The Missing Luminous Blue Variables and the Bistability Jump
• First science with SALT: peering at the accreting polar caps of the eclipsing polar SDSS J015543.40+002807.2
• Strong Emission Line HII Galaxies in the Sloan Digital Sky Survey. I. Catalog of DR1 Objects with Oxygen Abundances from Te easurements
• Ages and Luminosities of Young SMC/LMC Star Clusters and the recent Star Formation History of the Clouds
• L-band spectroscopy of Galactic OB-stars
• Spectrophotometry of Sextans A and B: Chemical Abundances of HII Regions and Planetary Nebulae
• On the nature of the prototype LBV AG Carinae I. Fundamental parameters during visual minimum phases and changes in the bolometric luminosity during the S-Dor cycle
• A Hidden Population of Massive Stars with Circumstellar Shells Discovered with the Spitzer Space Telescope
• MN48: a new Galactic bona fide luminous blue variable revealed by Spitzer and SALT
• The nature of B supergiants: clues from a steep drop in rotation rates at 22000 K. The possibility of Bi-stability braking
• Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars
• Chemical composition and origin of nebulae around Luminous Blue Variables
• Field O stars: formed in situ or as runaways?
• The metallicity extremes of the Sagittarius dSph using SALT spectroscopy of PNe
• 3-D radiative transfer in clumped hot star winds I. Influence of clumping on the resonance line formation
• On the Social Traits of Luminous Blue Variables
• A representative sample of Be Stars I: Sample Selection, Spectral Classification and Rotational Velocities
• A FUSE Survey of the Rotation Rates of Very Massive Stars in the Small and Large Magellanic Clouds
• Bona-fide, strong-variable galactic Luminous Blue Variable stars are fast rotators: detection of a high rotational velocity in HR Carinae
• The evolutionary status of Sher25 - implications for blue supergiants and the progenitor of SN1987A
• Massive runaway stars in the Large Magellanic Cloud
• On the formation of CIII 4647-50-51 and CIII 5696 in O star atmospheres
• Massive runaway stars in the Small Magellanic Cloud
• Classification of O Stars in the Yellow-Green: The Exciting Star VES 735
• Discovery of two new Galactic candidate luminous blue variables with WISE
• The blue supergiant Sher 25 and its intriguing hourglass nebula
• The ultraviolet and optical spectra of luminous B-type stars in the Small Magellanic Cloud
• The ISM Interactions of a Runaway LBV Nebula in the LMC
• The blue supergiant MN18 and its bipolar circumstellar nebula
• TYC 3159-6-1: a runaway blue supergiant
• Sher 25: pulsating but apparently alone
• WS1: one more new Galactic bona fide luminous blue variable
• Discovery of a new Wolf-Rayet star and a candidate star cluster in the Large Magellanic Cloud with Spitzer
• Tracing back the evolution of the candidate LBV HD168625

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• X-Shooting ULLYSES: massive stars at low metallicity. I. Project Description
• X-Shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive stars
• Short Term Variability of Evolved Massive Stars with TESS
• X-Shooting ULLYSES: Massive stars at low metallicity. IV. Spectral analysis methods and exemplary results for O stars
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• Unveiling the nitrogen-rich massive star in the metal-poor galaxy NGC 4068
• The contribution by luminous blue variable stars to the dust content of the Magellanic Clouds
• An unusually large gaseous transit in a debris disc
• X-Shooting ULLYSES: Massive Stars at Low Metallicity: XI. Pipeline-determined Physical Properties of Magellanic Cloud OB Stars
• HST/COS Spectra of the Wind Lines of VFTS 102 and 285
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