Could kilomasers pinpoint supermassive stars?

Abstract

A strong nuclear kilomaser, W1, has been found in the nearby galaxy NGC 253, associated with a forming super star cluster. Kilomasers could arise from the accretion disc around supermassive stars (>10^3 Msun), hypothetical objects that have been proposed as polluters responsible for the chemical peculiarities in globular clusters. The supermassive stars would form via runaway collisions, simultaneously with the cluster. Their discs are perturbed by stellar flybys, inspiralling and colliding stars. This raises the question if an accretion disc would at all be able to survive in such a dynamic environment and mase water lines. We investigated what the predicted maser spectrum of such a disc would look like using 2D hydrodynamic simulations and compared this to the W1 kilomaser. We derived model maser spectra from the simulations by using a general maser model for appropriate disc temperatures. All our model discs survived. The model maser spectra for the most destructive case for the simulations of M = 1000 Msun are a reasonable match with the W1 kilomaser spectrum in terms of scaling, flux values and some of the signal trends. Details in the spectrum suggest that a star of a few 1000 Msun might fit even better, with 10,000 Msun clearly giving too large velocities. Our investigations thus support the hypothesis that kilomasers could pinpoint supermassive stars.

14 pages, 7 figures

References in corpus (25)

• PLUTO: a Numerical Code for Computational Astrophysics
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Stellar Models and Yields of Asymptotic Giant Branch Stars
• Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
• Studying the YMC population of M83: how long clusters remain embedded, their interaction with the ISM and implications for GC formation theories
• A General Abundance Problem for All Self-Enrichment Scenarios for the Origin of Multiple Populations in Globular Clusters
• Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
• The Physics of Star Cluster Formation and Evolution
• CNO abundances in the globular clusters NGC 1851 and NGC 6752
• The Megamaser Cosmology Project. VI. Observations of NGC 6323
• The Parsec-scale Accretion Disk in NGC 3393
• The Chemical Evolution of Helium in Globular Clusters: Implications for the Self-Pollution Scenario
• The primordial and evolutionary abundance variations in globular-cluster stars: a problem with two unknowns
• The Megamaser Cosmology Project.IX. Black hole masses for three maser galaxies
• Revisiting nucleosynthesis in globular clusters: the case of NGC 2808 and the role of He and K
• The evolution of protoplanetary discs in star formation and feedback simulations
• Multiple stellar populations and their evolution in globular clusters: A nucleosynthesis perspective
• Evidence of a pure starburst nature of the nuclear region of NGC 253
• Maximally accreting supermassive stars: a fundamental limit imposed by hydrostatic equilibrium
• Formation of freely floating sub-stellar objects via close encounters
• Spectral properties and detectability of supermassive stars in protoglobular clusters at high redshift
• Ubiquitous Water Masers in Nearby Star-Forming Galaxies
• ALMA observations of the Extended Green Object G19.01$-$0.03: I. A Keplerian disc in a massive protostellar system
• The inner circumstellar disk of the UX Ori star V1026 Sco