The little-studied cluster Berkeley 90. I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Abstract

Context: It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find due to their low numbers throughout the Galaxy and the implied large distances and extinctions. AIMS: We want to study: [a] LS III +46 11, identified in this paper as a very massive binary; [b] another nearby massive system, LS III +46 12; and [c] the surrounding stellar cluster, Berkeley 90. Methods: Most of the data used in this paper are multi-epoch high-S/N optical spectra though we also use Lucky Imaging and archival photometry. The spectra are reduced with devoted pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results: LS III +46 11 is identified as a new very-early-O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 12 and derive minimum masses of 38.80$\pm$0.83 M_Sol and 35.60$\pm$0.77 M_Sol for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system, where the companion is currently undetected.

arXiv commentAccepted for publication in A&A

References in corpus (36)

• On the variation of the Initial Mass Function
• Correcting for the Effects of Interstellar Extinction
• Binary interaction dominates the evolution of massive stars
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• The WASP Project and the SuperWASP Cameras
• A new calibration of stellar parameters of Galactic O stars
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit
• Database of Geneva stellar evolution tracks and isochrones for UBVRIJHKLL'M, HST-WFPC2, Geneva and Washington photometric systems
• Northern Sky Variability Survey (NSVS): Public data release
• 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
• The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-Violet at R~2500
• The maximum stellar mass, star-cluster formation and composite stellar populations
• The Second Data Release of the INT Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS DR2)
• WR 20a is an Eclipsing Binary: Accurate Determination of Parameters for an Extremely Massive Wolf-Rayet System
• CHORIZOS: a CHi-square cOde for parameteRized modelIng and characteriZation of phOtometry and Spectrophotometry
• Spectral Classification of O2-3.5If*/WN5-7 stars
• The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars
• WR20a: a massive cornerstone binary system comprising two extreme early-type stars
• The VLT-FLAMES Tarantula Survey XIV. The O-Type Stellar Content of 30 Doradus
• IPHAS and the symbiotic stars. I. Selection method and first discoveries
• Visual/infrared interferometry of Orion Trapezium stars: Preliminary dynamical orbit and aperture synthesis imaging of the Theta 1 Orionis C system
• The very massive binary NGC3603-A1
• New very massive stars in Cygnus OB2
• Pismis 24-1: The Stellar Upper Mass Limit Preserved
• A search for counterparts to massive X-ray binaries using photometric catalogues
• Orbital and physical properties of the $\sigma$ Ori Aa,Ab,B triple system
• High-resolution imaging of Galactic massive stars with AstraLux. I. 138 fields with delta > -25 degrees
• Evidence for a physically bound third component in HD 150136
• The non-thermal radio emitter HD 93250 resolved by long baseline interferometry
• The VLT-FLAMES Tarantula Survey II: R139 revealed as a massive binary system
• Three-dimensional orbits of the triple-O stellar system HD 150136
• The Nearest Star of spectral type O3: A Component of the Multiple System HD 150136
• Direct Detection of the Tertiary Component in the Massive Multiple HD 150 136 with VLTI
• The IACOB spectroscopic database of Galactic OB stars

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• The Galactic O-Star Spectroscopic Survey (GOSSS). III. 142 additional O-type systems
• A search for Galactic runaway stars using Gaia Data Release 1 and Hipparcos proper motions
• MONOS: Multiplicity Of Northern O-type Spectroscopic systems. I. Project description and spectral classifications and visual multiplicity of previously known objects
• Optical-NIR dust extinction towards Galactic O stars
• The Villafranca catalog of Galactic OB groups. II. From Gaia DR2 to EDR3 and ten new systems with O stars
• The Arches cluster revisited: I. Data presentation and stellar census
• The Villafranca catalog of Galactic OB groups: I. Systems with O2-O3.5 stars
• Extreme infrared variables from UKIDSS - II. an end-of-survey catalogue of eruptive YSOs and unusual stars
• A close encounter of the massive kind
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• Gaia-ESO Survey: global properties of clusters Trumpler 14 and 16 in the Carina Nebula
• Stellar population of the superbubble N206 in the LMC I. Analysis of the Of-type stars
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• The Arches cluster revisited: IV. Observational constraints on the binary properties of very massive stars
• The little-studied cluster Berkeley 90. II. The foreground ISM
• The little-studied cluster Berkeley 90. III. Cluster parameters
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