EVOLUTION OF MASSIVE PROTOSTARS VIA DISK ACCRETION

By T. Hosokawa, H. Yorke, K. Omukai. 2010

158 citations recorded by the source corpus.

Mass accretion onto (proto-)stars at high accretion rates 10^{-4}\, M_{\odot }\,{\rm yr}^{-1}$?> is expected in massive star formation. We study the evolution of massive protostars at such high rates by numerically solving the stellar structure equations. In this paper, we examine the evolution via disk accretion. We consider a limiting case of “cold” disk accretion, whereby most of the stellar photosphere can radiate freely with negligible backwarming from the accretion flow, and the accreting material settles onto the star with the same specific entropy as the photosphere. We compare our results to the calculated evolution via spherically symmetric accretion, the opposite limit, whereby the material accreting onto the star contains the entropy produced in the accretion shock front. We examine how different accretion geometries affect the evolution of massive protostars. For cold disk accretion at 10−3 M☉ yr−1, the radius of a protostar is initially small, R*≃ a few R☉. After several solar masses have accreted, the protostar begins to bloat up and for M* ≃ 10 M☉ the stellar radius attains its maximum of 30–400 R☉. The large radius ∼100 R☉ is also a feature of spherically symmetric accretion at the same accreted mass and accretion rate. Hence, expansion to a large radius is a robust feature of accreting massive protostars. At later times, the protostar eventually begins to contract and reaches the zero-age main sequence (ZAMS) for M* ≃ 30 M☉, independent of the accretion geometry. For accretion rates exceeding several 10−3 M☉ yr−1, the protostar never contracts to the ZAMS. The very large radius of several hundreds R☉ results in the low effective temperature and low UV luminosity of the protostar. Such bloated protostars could well explain the existence of bright high-mass protostellar objects, which lack detectable H ii regions.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ad9fea99cdc6ae00aa2437dd193b49cdc3a41267

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In Astronomy and Astrophysics

1. Volker Bromm
2. A. Stacy
3. Thomas Greif
4. Naoki Yoshida
5. Aaron T. Lee
6. T. Hosokawa
7. H. Yorke
8. K. Omukai

Citations in the corpus

• THE RED MSX SOURCE SURVEY: THE MASSIVE YOUNG STELLAR POPULATION OF OUR GALAXY (2013, background): “We also find a maximum luminosity for a massive YSO of about 2 × 105 L⊙, that is consistent with the Davies et al. and Hosokawa et al. (2010) models (Mottram et al. 2011b).”
• FORMATION OF MASSIVE PRIMORDIAL STARS: INTERMITTENT UV FEEDBACK WITH EPISODIC MASS ACCRETION (2015, background): “Varying the characteristics of the initial model (mass, radius, entropy, etc.) only affects the early evolution long before stellar UV feedback begins to operate (e.g., Hosokawa et al. 2010).”
• Disk-mediated accretion burst in a high-mass young stellar object (2016, background): “The inferred value is likely a lower limit, as the radius of a massive protostar should be several times larger than that of a main sequence star (24; 25).”
• FORMATION OF PRIMORDIAL SUPERMASSIVE STARS BY RAPID MASS ACCRETION (2013, methodology): “This abrupt expansion in the cold-accretion limit is related to the extension of a deuterium-burning layer in the stellar interior, which is studied in detail in Hosokawa et al. (2010).”
• Accretion disks in luminous young stellar objects (2015, background): “We ignore therefore the possibility that the objects are swollen up because of high accretion rates (Hosokawa et al., 2010).”
• Building up the Population III initial mass function from cosmological initial conditions (2016, methodology): “1 given a constant Ṁ = 10−3M⊙yr −1 and 10−4M⊙yr −1, allowing for direct comparison to the full calculation done by Hosokawa et al. (2010).”
• The First Stars: Mass Growth Under Protostellar Feedback (2011, methodology): “While Hosokawa et al. (2010) find that a massive (∼ 10 M⊙) accreting protostar will typically contract to the ZAMS radius on timescales of ∼ 104 yr, in our model we set our protostar to the ZAMS values much earlier.”
• 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).”
• ATLASGAL — towards a complete sample of massive star forming clumps ⋆ (2014, methodology): “This is consistent with the models of Hosokawa & Omukai (2009) and Hosokawa et al. (2010) described in the Introduction of this paper and, indeed, it is clear from the plots shown in Fig.”