Volume 625, May 2019
|Number of page(s)||6|
|Section||Letters to the Editor|
|Published online||01 May 2019|
Letter to the Editor
The origin of very massive stars around NGC 3603
Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile
2 Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
3 Armagh Observatory, College Hill, Armagh BT61 9DG, UK
4 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago, Chile
5 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
Accepted: 2 April 2019
The formation mechanism of the most massive stars in the Universe remains an unsolved problem. Are they able to form in relative isolation in a manner similar to the formation of solar-type stars, or do they necessarily require a clustered environment? In order to shed light on this important question, we study the origin of two very massive stars (VMS): the O2.5If*/WN6 star RFS7 (∼100 M⊙), and the O3.5If* star RFS8 (∼70 M⊙), found within ∼53 and 58 pc, respectively, of the Galactic massive young cluster NGC 3603, using Gaia data. The star RFS7 is found to exhibit motions resembling a runaway star from NGC 3603. This is now the most massive runaway star candidate known in the Milky Way. Although RFS8 also appears to move away from the cluster core, it has proper-motion values that appear inconsistent with being a runaway from NGC 3603 at the 3σ level (but with substantial uncertainties due to distance and age). Furthermore, no evidence for a bow-shock or a cluster was found surrounding RFS8 from available near-infrared photometry. In summary, whilst RFS7 is likely a runaway star from NGC 3603, making it the first VMS runaway in the Milky Way, RFS8 is an extremely young (∼2 Myr) VMS, which might also be a runaway, but this would need to be established from future spectroscopic and astrometric observations, as well as precise distances. If RFS 8 was still not found to meet the criteria for being a runaway from NGC 3603 from such future data, this would have important ramifications for current theories of massive star formation, as well as the way the stellar initial mass function is sampled.
Key words: stars: kinematics and dynamics / stars: formation
© ESO 2019
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