The blue supergiant MN18 and its bipolar circumstellar nebula

Abstract

We report the results of spectrophotometric observations of the massive star MN18 revealed via discovery of a bipolar nebula around it with the Spitzer Space Telescope. Using the optical spectrum obtained with the Southern African Large Telescope, we classify this star as B1 Ia. The evolved status of MN18 is supported by the detection of nitrogen overabundance in the nebula, which implies that it is composed of processed material ejected by the star. We analysed the spectrum of MN18 by using the code CMFGEN, obtaining a stellar effective temperature of \approx 21 kK. The star is highly reddened, E(B-V)\approx 2 mag. Adopting an absolute visual magnitude of M_V=-6.8\pm0.5 (typical of B1 supergiants), MN18 has a luminosity of log L/Lsun \approx 5.42\pm0.30, a mass-loss rate of \approx (2.8-4.5)\times10^{-7} Msun/yr, and resides at a distance of \approx 5.6^{+1.5} _{-1.2} kpc. We discuss the origin of the nebula around MN18 and compare it with similar nebulae produced by other blue supergiants in the Galaxy (Sher 25, HD 168625, [SBW2007] 1) and the Large Magellanic Cloud (Sk-69 202). The nitrogen abundances in these nebulae imply that blue supergiants can produce them from the main sequence stage up to the pre-supernova stage. We also present a K-band spectrum of the candidate luminous blue variable MN56 (encircled by a ring-like nebula) and report the discovery of an OB star at \approx 17 arcsec from MN18. The possible membership of MN18 and the OB star of the star cluster Lynga 3 is discussed.

21 pages, 14 figures, accepted for publication in MNRAS

References in corpus (25)

• Binary interaction dominates the evolution of massive stars
• Pre-Supernova Evolution of Massive Single and Binary Stars
• The High Angular Resolution Multiplicity of Massive Stars
• UBVJHK synthetic photometry of Galactic O stars
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• First science with SALT: peering at the accreting polar caps of the eclipsing polar SDSS J015543.40+002807.2
• Luminous Blue Variables as the progenitors of supernovae with quasi-periodic radio modulations
• Luminous Blue Variables and superluminous supernovae from binary mergers
• Discovery of a nearby twin of SN1987A's nebula around the luminous blue variable HD168625: Was Sk--69 202 an LBV?
• The VLT-FLAMES Tarantula Survey III: A very massive star in apparent isolation from the massive cluster R136
• Multiple ring nebulae around blue supergiants
• The metallicity extremes of the Sagittarius dSph using SALT spectroscopy of PNe
• Interacting supernovae from photoionization-confined shells around red supergiant stars
• The Destruction of the Circumstellar Ring of SN 1987A
• And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and the Waists of Bipolar Nebulae
• Evolution of Collisionally Merged Massive Stars
• Time evolution of the line emission from the inner circumstellar ring of SN 1987A and its hot spots
• Radial dependence of line profile variability in seven O9--B0.5 stars
• On the H$\alpha$ Behaviour of Blue Supergiants: Rise and Fall over the Bi-stability Jump
• The blue supergiant Sher 25 and its intriguing hourglass nebula
• Photometry of seven overlooked open clusters in the First and Fourth Galactic Quadrants
• Sher 25: pulsating but apparently alone
• WS1: one more new Galactic bona fide luminous blue variable
• WR 120bb and WR 120bc: a pair of WN9h stars with possibly interacting circumstellar shells
• Discovery of a new Galactic bona fide luminous blue variable with Spitzer

Cited by in corpus (14)

• MN48: a new Galactic bona fide luminous blue variable revealed by Spitzer and SALT
• The multi-faceted Type II-L supernova 2014G from pre-maximum to nebular phase
• Dead or Alive? Long-term evolution of SN 2015bh (SNhunt275)
• The quest for blue supergiants: binary merger models for the evolution of the progenitor of SN 1987A
• Infrared Continuum and Line Evolution of the Equatorial Ring around SN 1987A
• The spectacular evolution of Supernova 1996al over 15 years: a low energy explosion of a stripped massive star in a highly structured environment
• Optical spectroscopy of the blue supergiant Sk-69 279 and its circumstellar shell with SALT
• PION: Simulating bow shocks and circumstellar nebulae
• Exploring the multifaceted circumstellar environment of the Luminous Blue Variable HR Carinae
• Unveiling the nitrogen-rich massive star in the metal-poor galaxy NGC 4068
• The Luminous Blue Variable RMC127 as seen with ALMA and ATCA
• UV spectroscopy of the blue supergiant SBW1: the remarkably weak wind of a SN 1987A analog
• Two circumstellar nebulae discovered with the Wide-field Infrared Survey Explorer and their massive central stars
• HD 93795: a late-B supergiant star with a square circumstellar nebula