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Title: RAPIDLY ACCRETING SUPERGIANT PROTOSTARS: EMBRYOS OF SUPERMASSIVE BLACK HOLES?

Abstract

Direct collapse of supermassive stars (SMSs) is a possible pathway for generating supermassive black holes in the early universe. It is expected that an SMS could form via very rapid mass accretion with M-dot{sub *} {approx} 0.1-1 M{sub Sun} yr{sup -1} during the gravitational collapse of an atomic-cooling primordial gas cloud. In this paper, we study how stars would evolve under such extreme rapid mass accretion, focusing on the early evolution until the stellar mass reaches 10{sup 3} M{sub Sun }. To this end, we numerically calculate the detailed interior structure of accreting stars with primordial element abundances. Our results show that for accretion rates higher than 10{sup -2} M{sub Sun} yr{sup -1}, stellar evolution is qualitatively different from that expected at lower rates. While accreting at these high rates, the star always has a radius exceeding 100 R{sub Sun }, which increases monotonically with the stellar mass. The mass-radius relation for stellar masses exceeding {approx}100 M{sub Sun} follows the same track with R{sub *}{proportional_to}M {sup 1/2}{sub *} in all cases with accretion rates {approx}> 10{sup -2} M{sub Sun} yr{sup -1}; at a stellar mass of 10{sup 3} M{sub Sun }, the radius is {approx_equal} 7000 R{sub Sun} ({approx_equal} 30more » AU). With higher accretion rates, the onset of hydrogen burning is shifted toward higher stellar masses. In particular, for accretion rates exceeding M-dot{sub *}{approx}>0.1 M{sub Sun} yr{sup -1}, there is no significant hydrogen burning even after 10{sup 3} M{sub Sun} have accreted onto the protostar. Such 'supergiant' protostars have effective temperatures as low as T{sub eff} {approx_equal} 5000 K throughout their evolution and because they hardly emit ionizing photons, they do not create an H II region or significantly heat their immediate surroundings. Thus, radiative feedback is unable to hinder the growth of rapidly accreting stars to masses in excess of 10{sup 3} M{sub Sun} as long as material is accreted at rates M-dot{sub *}{approx}>10{sup -2} M{sub Sun} yr{sup -1}.« less

Authors:
;  [1];  [2]
  1. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
  2. Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)
Publication Date:
OSTI Identifier:
22092429
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 756; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ASTRONOMY; ASTROPHYSICS; BLACK HOLES; COSMOLOGY; ELEMENT ABUNDANCE; GALAXIES; GRAVITATIONAL COLLAPSE; H2 REGIONS; HYDROGEN BURNING; MASS; PHOTON EMISSION; PROTOSTARS; STAR ACCRETION; STAR EVOLUTION; SUPERMASSIVE STARS; UNIVERSE

Citation Formats

Hosokawa, Takashi, Yorke, Harold W., and Omukai, Kazuyuki. RAPIDLY ACCRETING SUPERGIANT PROTOSTARS: EMBRYOS OF SUPERMASSIVE BLACK HOLES?. United States: N. p., 2012. Web. doi:10.1088/0004-637X/756/1/93.
Hosokawa, Takashi, Yorke, Harold W., & Omukai, Kazuyuki. RAPIDLY ACCRETING SUPERGIANT PROTOSTARS: EMBRYOS OF SUPERMASSIVE BLACK HOLES?. United States. https://doi.org/10.1088/0004-637X/756/1/93
Hosokawa, Takashi, Yorke, Harold W., and Omukai, Kazuyuki. 2012. "RAPIDLY ACCRETING SUPERGIANT PROTOSTARS: EMBRYOS OF SUPERMASSIVE BLACK HOLES?". United States. https://doi.org/10.1088/0004-637X/756/1/93.
@article{osti_22092429,
title = {RAPIDLY ACCRETING SUPERGIANT PROTOSTARS: EMBRYOS OF SUPERMASSIVE BLACK HOLES?},
author = {Hosokawa, Takashi and Yorke, Harold W. and Omukai, Kazuyuki},
abstractNote = {Direct collapse of supermassive stars (SMSs) is a possible pathway for generating supermassive black holes in the early universe. It is expected that an SMS could form via very rapid mass accretion with M-dot{sub *} {approx} 0.1-1 M{sub Sun} yr{sup -1} during the gravitational collapse of an atomic-cooling primordial gas cloud. In this paper, we study how stars would evolve under such extreme rapid mass accretion, focusing on the early evolution until the stellar mass reaches 10{sup 3} M{sub Sun }. To this end, we numerically calculate the detailed interior structure of accreting stars with primordial element abundances. Our results show that for accretion rates higher than 10{sup -2} M{sub Sun} yr{sup -1}, stellar evolution is qualitatively different from that expected at lower rates. While accreting at these high rates, the star always has a radius exceeding 100 R{sub Sun }, which increases monotonically with the stellar mass. The mass-radius relation for stellar masses exceeding {approx}100 M{sub Sun} follows the same track with R{sub *}{proportional_to}M {sup 1/2}{sub *} in all cases with accretion rates {approx}> 10{sup -2} M{sub Sun} yr{sup -1}; at a stellar mass of 10{sup 3} M{sub Sun }, the radius is {approx_equal} 7000 R{sub Sun} ({approx_equal} 30 AU). With higher accretion rates, the onset of hydrogen burning is shifted toward higher stellar masses. In particular, for accretion rates exceeding M-dot{sub *}{approx}>0.1 M{sub Sun} yr{sup -1}, there is no significant hydrogen burning even after 10{sup 3} M{sub Sun} have accreted onto the protostar. Such 'supergiant' protostars have effective temperatures as low as T{sub eff} {approx_equal} 5000 K throughout their evolution and because they hardly emit ionizing photons, they do not create an H II region or significantly heat their immediate surroundings. Thus, radiative feedback is unable to hinder the growth of rapidly accreting stars to masses in excess of 10{sup 3} M{sub Sun} as long as material is accreted at rates M-dot{sub *}{approx}>10{sup -2} M{sub Sun} yr{sup -1}.},
doi = {10.1088/0004-637X/756/1/93},
url = {https://www.osti.gov/biblio/22092429}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 756,
place = {United States},
year = {Sat Sep 01 00:00:00 EDT 2012},
month = {Sat Sep 01 00:00:00 EDT 2012}
}