The most massive stars in the Arches cluster

By Fabrice Martins, D. John Hillier, T. Paumard, F. Eisenhauer, T. Ott, R. Genzel. 2007

149 citations recorded by the source corpus.

Aims. We study a sample composed of 28 of the brightest stars in the Arches cluster. Our aim is to constrain their stellar and wind properties and to establish their nature and evolutionary status. Methods. We analyze K -band spectra obtained with the integral field spectrograph SINFONI on the VLT. Atmosphere models computed with the code CMFGEN are used to derive the effective temperatures, luminosities, stellar abundances, mass loss rates and wind terminal velocities. Results. We find that the stars in our sample are either H-rich WN7–9 stars (WN7–9h) or supergiants, where two are classified as OIf + . All stars are 2-4 Myr old. There is marginal evidence for a younger age among the most massive stars. The WN7-9h stars reach luminosities as high as 2 $\times$ 10 6  $L_{\odot}$, consistent with initial masses of ~120 $M_{\odot}$. They are still quite H-rich, but show both N enhancement and C depletion. They are thus identified as core H-burning objects showing products of the CNO equilibrium on their surface. Their progenitors are most likely supergiants of spectral types earlier than O4-6 and initial masses >60 $M_{\odot}$. Their winds follow a well-defined modified wind momentum – luminosity relation (WLR): this is a strong indication that they are radiatively driven. Stellar abundances tend to favor a slightly super-solar metallicity, at least for the lightest metals. We note, however, that the evolutionary models seem to under-predict the degree of N enrichment.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/9db3ee1e69a343886cf346417dbde672152d9a3e

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In Astronomy and Astrophysics

1. Selma de Mink
2. N. Langer
3. N. Smith
4. Michela Mapelli
5. P. Crowther
6. J. Vink
7. G. Meynet
8. W. Hamann

Citations in the corpus

• The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 M⊙ stellar mass limit (2010, methodology): “In Table 8 we provide the inferred properties of F6 and F9 on the basis of these photometric properties plus the stellar temperatures and K-band bolometric corrections derived by Martins et al. (2008).”
• The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of He II λ1640 in young star clusters (2016, background): “The short lifetime of such stars (2–3 Myr; Yusof et al. 2013) restricts suitable Milky Way star clusters to only a handful, including the Arches (Martins et al. 2008) and NGC 3603 (Schnurr et al. 2008), both of which are E-mail: Paul.crowther@sheffield.ac.uk highly reddened.”
• On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk (2014, background): “The above scenario concerning the iron abundance gradient of young stellar tracers shows a stark difference when compared with iron abundances of young stars (red supergiants, luminous blue variables, Wolf–Rayet and O-type stars) located either in the Nuclear Bulge or in the near end of the Galactic”
• Wind modelling of very massive stars up to 300 solar masses (2011, background): “As the O4-O6 supergiants from the Martins et al. (2008) analysis have e ff ective temperatures in the range 32-40 kK, we expect ∞ to fall in the range 2500-3500 km s − 1 (see Fig.”
• Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit (2008, background): “Also the bright WNL stars in the Arches cluster (Najarro et al. 2004; Martins et al. 2008) and in R 136a (de Koter et al. 1997) fall into the same category as WR 22 and WR 25 – extremely luminous H-rich WNL stars with relatively weak emission lines.”
• The Wolf-Rayet stars in the Large Magellanic Cloud - A comprehensive analysis of the WN class (2014, background): “While the LMC stars are represented by color-filled symbols, the open symbols in the background are the Galactic WN stars analyzed by HGL06, Martins et al. (2008), Liermann et al. (2010), and Barniske et al. (2008).”
• STAR FORMATION IN MASSIVE CLUSTERS VIA THE WILKINSON MICROWAVE ANISOTROPY PROBE AND THE SPITZER GLIMPSE SURVEY (2009, background): “Since many clusters harbor stars with mass in excessof 100M⊙, but neither paper models stars withM > 88M⊙, we have added the result of Martins et al. (2008), who findQ≈ 1050 for each of four WN7-8h stars with logL/L⊙ > 6.3 (all of which they model by stars withM & 120M⊙; see their table 2 and…”
• The relation between the most-massive star and its parental star cluster mass (2009, unknown): “This massive cluster (∼ 1.2 ·104 M⊙, Figer et al. 1999; Liermann et al. 2009) hosts the Pistol star which is one of the brightest and most massive stars in the Galaxy (150+ M⊙?) but is believed to be 4-6 Myr old and therefore too old for this study.”
• The Galactic WC stars Stellar parameters from spectral analyses indicate a new evolutionary sequence (2012, background): “Since we know WNL stars with very different hydrogen abundances (Hamann et al. 2006; Martins et al. 2008; Liermann et al. 2010), it is likely that there are multiple excursions between a quiet WNL stage and LBV eruptions, as indicated by the double-side arrow in Eq.”