The Double-Lined Spectrum of LBV 1806-20

Abstract

Despite much theoretical and observational progress, there is no known firm upper limit to the masses of stars. Our understanding of the interplay between the immense radiation pressure produced by massive stars in formation and the opacity of infalling material is subject to theoretical uncertainties, and many observational claims of ``the most massive star'' have failed the singularity test. LBV 1806-20 is a particularly luminous object, L~10^6 Lsun, for which some have claimed very high mass estimates (M_initial>200 Msun), based, in part, on its similarity to the Pistol Star. We present high-resolution near-infrared spectroscopy of LBV 1806-20, showing that it is possibly a binary system with components separated in velocity by ~70 kms. If correct, then this system is not the most massive star known, yet it is a massive binary system. We argue that a binary, or merged, system is more consistent with the ages of nearby stars in the LBV 1806-20 cluster. In addition, we find that the velocity of V_LSR=36 kms is consistent with a distance of 11.8 kpc, a luminosity of 10^6.3 Lsun, and a system mass of ~130 Msun.

arXiv commentApJL, accepted

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• Massive Stars in the SGR 1806-20 Cluster
• Periastron Passage Triggering of the 19th Century Eruptions of Eta Carinae
• Pulsar-wind nebulae and magnetar outflows: observations at radio, X-ray, and gamma-ray wavelengths
• The distances of short-hard GRBs and the SGR connection
• Pure and loaded fireballs in SGR giant flares
• SGRs in nearby galaxies: rate, luminosity function and fraction among short GRBs
• Proper Motions and Origins of SGR 1806-20 and SGR 1900+14
• The first X-ray survey of Galactic Luminous Blue Variables
• Constraints on the distance to SGR 1806-20 from HI absorption
• Extended VHE gamma-ray emission towards SGR1806-20, LBV1806-20, and stellar cluster Cl*1806-20
• Luminous blue variables: An imaging perspective on their binarity and near environment
• SGR 1806-20 distance and dust properties in molecular clouds by analysis of a flare x-ray echoes
• A deep near-infrared spectroscopic survey of the Scutum-Crux arm for Wolf-Rayet stars
• Contamination of short GRBs by giant magnetar flares: Significance of downward revision in distance to SGR 1806-20
• VVV analysis of star clusters towards the W31 star-forming complex
• The Stellar Initial Mass Function in the Galactic Center
• The Outcome of the Protoplanetary Disk of Very Massive Stars