A new calibration of stellar parameters of Galactic O stars

By Fabrice Martins, Daniel Schaerer, D. John Hillier. 2005

889 citations recorded by the source corpus.

We present new calibrations of stellar parameters of O stars at solar metallicity taking non-LTE, wind, and line-blanketing effects into account. Gravities and absolute visual magnitudes are derived from results of recent spectroscopic analyses. Two types of effective temperature scales are derived: one from a compilation based on recent spectroscopic studies of a sample of massive stars – the “observational scale” – and the other from direct interpolations on a grid of non-LTE spherically extended line-blanketed models computed with the code CMFGEN (Hillier & Miller 1998) – the “theoretical scale”. These T eff scales are then further used together with the grid of models to calibrate other parameters (bolometric correction, luminosity, radius, spectroscopic mass and ionising fluxes) as a function of spectral type and luminosity class. Compared to the earlier calibrations of Vacca et al. (1996) the main results are: 
[–] The effective temperature scales of dwarfs, giants and supergiants are cooler by 2000 to 8000 K, the theoretical scale being slightly cooler than the observational one. The reduction is the largest for the earliest spectral types and for supergiants.
[–] Bolometric corrections as a function of T eff are reduced by 0.1 mag due to line blanketing which redistributes part of the UV flux in the optical range. For a given spectral type the reduction of BC is larger for early types and for supergiants. Typically BCs derived using the theoretical T eff scale are 0.40 to 0.60 mag lower than that of Vacca et al. (1996), whereas the differences using the observational T eff scale are somewhat smaller.
[–] Luminosities are reduced by 0.20 to 0.35 dex for dwarfs, by ~0.25 for all giants and by 0.25 to 0.35 dex for supergiants. The reduction is essentially the same for both T eff scales. It is independent of spectral type for giants and supergiants and is slightly larger for late type than for early type dwarfs.
[–] Lyman continuum fluxes are reduced. Our theoretical values for the hydrogen ionising photon fluxes for dwarfs are 0.20 to 0.80 dex lower than those of Vacca et al. (1996), the difference being larger at late spectral types. For giants the reduction is of 0.25 to 0.55 dex, while for supergiants it is of 0.30 to 0.55 dex. Using the observational T eff scale leads to smaller reductions at late spectral types.
 
The present results should represent a significant improvement over previous calibrations, given the detailed treatment of non-LTE line-blanketing in the expanding atmospheres of massive stars.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/224510acd011f4da29e372ef08927d4b58fd7fd7

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In Astronomy and Astrophysics

1. N. Smith
2. N. Langer
3. Selma de Mink
4. S. Smartt
5. P. Crowther
6. Mark R. Krumholz
7. C. Conroy
8. J. Vink

In Education

1. A. Herrero
2. N. Murray
3. M. Povich
4. P. Crowther
5. J. Puls
6. S. Simón-Díaz
7. M. Moe
8. R. Di Stefano

In Instrumentation

1. N. Langer
2. Selma de Mink
3. N. Smith
4. J. Vink
5. S. Smartt
6. J. Puls
7. P. Crowther
8. F. Najarro

Citations in the corpus

• TOWARD A UNIFICATION OF STAR FORMATION RATE DETERMINATIONS IN THE MILKY WAY AND OTHER GALAXIES (2011, methodology): “O star masses based on Mspec in stellar models could therefore be underestimates, particularly for the earliest spectral types (Martins et al. 2005).”
• The VLT-FLAMES survey of massive stars: evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds (2007, background): “Martins et al. (2005) have produced observational effective temperature scales for Galactic O-type stars and their O9.”
• Lower mass loss rates in O-type stars: Spectral signatures of dense clumps in the wind of two Galactic O4 stars (2004, background): “…& Bianchi methodology yields temperatures that are systematically lower than all other recent analyses of optical and UV spectra of O stars (see Heap et al. (2005) and Martins et al. (2005) who provide a detailed comparison of these studies and who are led to exclude Garcia & Bianchi results).”
• TOWARD COMPLETE STATISTICS OF MASSIVE BINARY STARS: PENULTIMATE RESULTS FROM THE CYGNUS OB2 RADIAL VELOCITY SURVEY (2014, methodology): “Masses for OB stars are taken from Martins et al. (2005) for O stars and Hunter et al. (2008) for early B stars.”
• STAR FORMATION IN MASSIVE CLUSTERS VIA THE WILKINSON MICROWAVE ANISOTROPY PROBE AND THE SPITZER GLIMPSE SURVEY (2009, methodology): “Using the ionizing flux given by Martins et al. (2005), we can integrate over a Muench et al. (2002)-like IMF (eqn.”
• The relation between the most-massive star and its parental star cluster mass (2009, methodology): “Note that the new calibration by Martins et al. (2005) is only provided up to a spectral type of O3.”
• A LIBRARY OF THEORETICAL ULTRAVIOLET SPECTRA OF MASSIVE, HOT STARS FOR EVOLUTIONARY SYNTHESIS (2010, methodology): “These spectral types were derived using the observational scale of Martins et al. (2005a) for O stars and the B-star scale of Conti et al. (2008, p. 54).”
• O stars with weak winds: the Galactic case (2005, background): “Except for the faintest, they have luminosities in reasonable agreement with the new calibration Teff - Luminosity of Martins et al. (2005).”
• A census of the Wolf–Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy (2006, methodology): “We follow the approach of from Schild & Maeder (1984) and Massey et al. (2001), updated to account for the revised spectral type–Teff calibration of Martins et al. (2005) for O stars, Crowther et al. (2006) for B supergiants, plus the high mass-loss Meynet et al. (1994) solar metallicity isochrones.”
• Bright OB stars in the Galaxy. III. Constraints on the radial stratification of the clumping factor (2006, methodology): “Based on this investigation, and deriving new spectral-type–Teff and spectral-type–logg calibrations (see also Martins et al. 2005), Markova et al. (2004, “Paper I”) extended this sample considerably and obtained a “new” empirical wind-momentum–luminosity relationship1(WLR; Kudritzki et al. 1995;…”
• Clustered and Triggered Star Formation in W5: Observations with Spitzer (2008, positive): “Adopting stellar parameters from Martins et al. (2005), an O7V star will have ionizing flux L49 = 0.43.”
• Lidov–Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems (2016, background): “We assume that the same statistics hold for the population of stars with >M M25 as for the population of O-stars, even though the latter category is slightly more inclusive, as O-star masses can be as small as 16 M (Martins et al. 2005).”
• The most massive stars in the Arches cluster (2007, background): “But larger values are also found: f = 0.2 by Repolust et al. (2004) orf = 0.1 by Crowther et al. (2002b); Martins et al. (2005b).”
• Physical parameters and wind properties of galactic early B supergiants (2005, methodology): “The fit to the combined sample (solid line) connects well to the recent Martins et al. (2005) relation for O stars (dotted line). of McErlean et al. (1999), based on hydrostatic, plane-parallel model atmospheres and derived Hαmass-loss rates with the un- blanketed version of FASTWIND (Santolaya-Rey…”
• Rotating massive main-sequence stars: II. Simulating a population of LMC early B-type stars as a test of rotational mixing (2011, background): “…massive main-sequence stars are yet to be understood, such as the winds of massive stars with luminosities below ∼105.2 L (e.g. Bouret et al. 2003; Martins et al. 2004, 2005; Mokiem et al. 2007; Puls et al. 2008), intermittent discrete absorption components in UV absorption lines (Prinja &…”