EVOLUTION OF MASSIVE PROTOSTARS WITH HIGH ACCRETION RATES

By T. Hosokawa, K. Omukai. 2008

271 citations recorded by the source corpus.

Formation of massive stars by accretion requires a high accretion rate of 10^{-4} M_{\odot }\, {\rm yr^{-1}}$?> to overcome the radiation pressure barrier of the forming stars. Here, we study evolution of protostars accreting at such high rates by solving the structure of the central star and the inner accreting envelope simultaneously. The protostellar evolution is followed starting from small initial cores until their arrival at the stage of the Zero-Age Main-Sequence (ZAMS) stars. An emphasis is put on evolutionary features different from those with a low accretion rate of , which is presumed in the standard scenario for low-mass star formation. With the high accretion rate of , the protostellar radius becomes very large and exceeds 100 R☉. Unlike the cases of low accretion rates, deuterium burning hardly affects the evolution, and the protostar remains radiative even after its ignition. It is not until the stellar mass reaches ≃40 M☉ that hydrogen burning begins and the protostar reaches the ZAMS phase, and this ZAMS arrival mass increases with the accretion rate. These features are similar to those of the first star formation in the universe, where high accretion rates are also expected, rather than to the present-day low-mass star formation. At a very high accretion rate of >3 × 10−3 M☉ yr-1, the total luminosity of the protostar becomes so high that the resultant radiation pressure inhibits the growth of the protostars under steady accretion before reaching the ZAMS stage. Therefore, the evolution under the critical accretion rate 3 × 10−3 M☉ yr-1 gives the upper mass limit of possible pre-main sequence stars at ≃60 M☉. The upper mass limit of MS stars is also set by the radiation pressure onto the dusty envelope under the same accretion rate at ≃250 M☉. We also propose that the central source enshrouded in the Orion KL/BN nebula has effective temperature and luminosity consistent with our model and is a possible candidate for such protostars growing under the high accretion rate.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/00e5ced7bfb3d8a03c470e0c5f0e987bd0a237c4

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Citations in the corpus

FORMATION OF MASSIVE PRIMORDIAL STARS: INTERMITTENT UV FEEDBACK WITH EPISODIC MASS ACCRETION (2015, methodology): “This differs from codes we used in HS11 and HR14, which employ shooting methods to solve the same equations (e.g., Omukai & Palla 2003; Hosokawa & Omukai 2009).”
Star formation rates and efficiencies in the Galactic Centre (2017, background): “…the accretion luminosity for low-mass young stars can be around an order of magnitude higher than the intrinsic stellar luminosity, whereas for high-mass stars the stellar luminosity dominates over the accretion luminosity for all reasonable accretion rates (>10 M ; e.g. Hosokawa & Omukai 2009).”
The RMS Survey: Ammonia and water maser analysis of massive star forming regions. ⋆ (2011, background): “Models suggest that high levels of accretion in the early stages of a massive star’s development lead to a ‘swelling up’ of theprotostellar core due to trapped entropy (e.g., Yorke & Bodenheimer 2008; Hosokawa & Omukai 2009; Hosokawa et al. 2010).”
CIRCUMVENTING THE RADIATION PRESSURE BARRIER IN THE FORMATION OF MASSIVE STARS VIA DISK ACCRETION (2010, methodology): “The upper mass limit of spherically symmetric accretion for our specific dust (Laor & Draine 1993) and stellar evolution model (Hosokawa & Omukai 2009) constrains the final stellar mass to be less than 40 M .”
THE MASS SPECTRUM OF THE FIRST STARS (2014, methodology): “The properties of a protostar are obtained based on the calculation by Hosokawa & Omukai (2009).”
EVOLUTION OF MASSIVE PROTOSTARS VIA DISK ACCRETION (2010, background): “In our previous work (Hosokawa & Omukai 2008; 2009, hereafter Paper I), we examined the evolution by numerically solving the interior structure of a protostar with a dusty accretion enve- lope under the assumption of spherical symmetry.”
FORMATION OF PRIMORDIAL SUPERMASSIVE STARS BY RAPID MASS ACCRETION (2013, methodology): “Recent theoretical work investigates how massive such primordial stars are, studying the late evolutionary stage whereby a protostar grows in mass via mass accretion from a surrounding envelope (e.g., 1 Department of Physics and Research Center for the Early Universe, The University of Tokyo, Tokyo ”
ONE HUNDRED FIRST STARS: PROTOSTELLAR EVOLUTION AND THE FINAL MASSES (2013, methodology): “The evolution of the protostar is calculated by numerically solving the interior structure with this accretion rate (e.g., Omukai & Palla 2003; Hosokawa & Omukai 2009).”
THE RED MSX SOURCE SURVEY: THE MASSIVE YOUNG STELLAR POPULATION OF OUR GALAXY (2013, background): “This deficit of ultraviolet photons is in agreement with models for massive YSOs which predict the star swells and cools as it accretes (eg Hosokawa & Omukai 2009).”
OUTFLOW FEEDBACK REGULATED MASSIVE STAR FORMATION IN PARSEC-SCALE CLUSTER-FORMING CLUMPS (2009, background): “In addition to overcoming the radiation pressure, a high accretion rate can also greatly modify the internal structure and appearance of a growing massive star (e.g., Hosokawa & Omukai 2009).”
SIMULATIONS ON A MOVING MESH: THE CLUSTERED FORMATION OF POPULATION III PROTOSTARS (2011, background): “During the early stages of protostellar evolution, Pop III stars grow rapidly in size from ≃ 10 to ≃ 100R⊙ (Hosokawa & Omukai 2009).”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “For more massive stars, it is essential to include accretion in the evolutionary calculations (Palla & Stahler 1992) and high accretion rates strongly affect the star’s evolution (Zinnecker & Yorke 2007; Hosokawa & Omukai 2009).”
RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: PROTOSTELLAR CORE FORMATION (2012, methodology): “…we have to modify our code, for example, by introducing the sink particle technique (Bate et al. 1995; Krumholz et al. 2004; Federrath et al. 2010) to replace the protostellar core with a subgrid stellar evolution model (e.g., Baraffe et al. 2002; Yorke & Bodenheimer 2008; Hosokawa & Omukai 2009).”
Formation and evolution of primordial protostellar systems (2012, background): “7, and are in the expected range of a few tens to 200 R (Hosokawa & Omukai 2009; Smith et al. 2011b).”
THE EFFECTS OF RADIATIVE TRANSFER ON LOW-MASS STAR FORMATION (2009, methodology): “The numerical parameters we use for the calculations in this paper are based on this calibration, but we note that after we began this work Hosokawa & Omukai (2009) published calculations suggesting that slightly different values would improve the model’s accuracy.”
H II REGIONS: WITNESSES TO MASSIVE STAR FORMATION (2010, methodology): “First, we use a ZAMS model to set the ionizing luminosity, while the models of Hosokawa & Omukai (2009) suggest that the protostellar radii of massive stars can be larger than the ZAMS value, leading to a smaller ionizing luminosity compared to the ZAMS value.”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, methodology): “Naively, the calculations discussed in the remainder of this paper using sink particles with accretion radii of 0.5 au underestimate the accretion luminosity by factors of 20–30 (taking protostellar accretion radii of 3–5 M ; Hosokawa & Omukai 2009).”
Physical Processes in the Interstellar Medium (2014, background): “As the radii of protostars usually are considerably larger than the radii of main sequence stars in the same mass range (Hosokawa & Omukai, 2009), this could be a viable option.”