Evolution of Massive Protostars With High Accretion Rates

Hosokawa, Takashi; Omukai, Kazuyuki

doi:10.1088/0004-637x/691/1/823

Cited by 383 publications

(577 citation statements)

References 58 publications

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“…Indeed, the luminosity derived from the spectral energy distribution (SED) of NIRS 3 (see Moreover, assuming that the mass of the central source is ∼20 M and its radius is equal to 10 R (approximately the radius of a ∼20 M star on the zero-age main sequence), from L acc we infer thatṀ acc is boosted to (5±2)×10 −3 M yr −1 (see Methods). The inferred value is probably a lower limit, as the radius of a massive protostar should be several times larger than that of a main sequence star 24,25 . Nevertheless, the inferred mass-accretion rate of this HMYSO burst is at least three orders of magnitude higher than those of EXors and MNors.…”

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confidence: 88%

Disk-mediated accretion burst in a high-mass young stellar object

et al. 2016

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Solar-mass stars form via disk-mediated accretion. Recent findings indicate that this process is probably episodic in the form of accretion bursts 1 , possibly caused by disk fragmentation 2-4 . Although it cannot be ruled out that high-mass young stellar objects arise from the coalescence of their low-mass brethren 5 , the latest results suggest that they more likely form via disks 6-9 . It follows that disk-mediated accretion bursts should occur 10,11 . Here we report on the discovery of the first disk-mediated accretion burst from a roughly twenty-solar-mass high-mass young stellar object 12 . Our near-infrared images show the brightening of the central source and its outflow cavities. Near-infrared spectroscopy reveals emission lines typical for accretion bursts in low-mass protostars, but orders of magnitude more luminous. Moreover, the released energy and the inferred mass-accretion rate are also orders of magnitude larger. Our results identify disk-accretion as the common mechanism of star formation across the entire stellar mass spectrum.S255IR NIRS 3 (aka S255IR-SMA1) is a well-studied ∼20 M (L bol ∼ 2.4×10 4 L ) high-mass young stellar object (HMYSO) 13,14 in the S255IR massive star-forming region 13 , located at a distance of ∼1.8 kpc 15 . It exhibits a disk-like rotating structure 13 , very likely an accretion disk, viewed nearly edge-on 16 (inclination angle ∼80 • ).A molecular outflow has been detected 13 (blueshifted lobe position angle (P.A.) ∼247 • ) perpendicular to the disk. Two bipolar lobes (cavities), cleared by the outflow, are illuminated by the central source and show up as reflection nebulae towards the southwest (blueshifted lobe) and northeast (redshifted lobe, see Fig.

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confidence: 88%

Disk-mediated accretion burst in a high-mass young stellar object

et al. 2016

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“…First, we consider the models for massive protostellar evolution with high accretion rates (≥10 −3 M yr −1 ) presented by Hosokawa & Omukai (2009) and Hosokawa et al (2010) for spherical collapse and accretion via a disc, respectively. Under both scenarios, massive protostars transition through a number of stages before joining the ZAMS.…”

Section: The Evolutionary Status Of the Ionising Sources In Sdc335mentioning

confidence: 99%

Tightening the belt: Constraining the mass and evolution in SDC335

Avison

Peretto

Fuller

et al. 2015

A&A

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Aims. Recent ALMA observations identified one of the most massive star-forming cores yet observed in the Milky Way: SDC335-MM1, within the infrared dark cloud SDC335.579-0.292. Along with an accompanying core MM2, SDC335 appears to be in the early stages of its star formation process. We aim to constrain the properties of the stars forming within these two massive millimetre sources. Methods. Observations of SDC335 at 6, 8, 23 and 25 GHz were made with the Australia Telescope Compact Array. We report the results of these continuum measurements, which combined with archival data, allow us to build and analyse the spectral energy distributions (SEDs) of the compact sources in SDC335. Results. Three hyper-compact H regions within SDC335 are identified, two of which are within the MM1 core. For each HCH region, we fit a free-free emission curve to the data, providing the derivation of the sources' emission measure, ionising photon flux, and electron density. Using these physical properties we assign each HCH region a zero-age main sequence (ZAMS) spectral type, finding two protostars with characteristics of spectral type B1.5 and one with a lower limit of B1-B1.5. Ancillary data from infrared to mm wavelength are used to construct free-free component subtracted SEDs for the mm-cores, which allows us to calculate the bolometric luminosities and revise the previous gas mass estimates. Conclusions. The measured luminosities for the two mm-cores are lower than expected from accreting sources displaying characteristics of the ZAMS spectral type assigned to them. The protostars are still actively accreting, suggesting that a mechanism is limiting the accretion luminosity. We present the case for two different mechanisms capable of causing lower than expected accretion luminosity. Finally, using the ZAMS mass values as lower limit constraints, a final stellar population for SDC335 was synthesised finding SDC335 is likely to be in the process of forming a stellar cluster comparable to the Trapezium cluster and NGC 6334 I(N).

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“…3) Accretion rates in the same ranges have been used by recent similar works modelling massive star formation through accretion. For instance, Hosokawa & Omukai (2009) calculate their pre-MS evolution with constant mass accretion rates spanning values between 10 −6 and 6×10 −3 M yr −1 .…”

Section: Mass Accretion Ratementioning

confidence: 99%

Star formation with disc accretion and rotation

Haemmerlé¹,

Eggenberger²,

Meynet³

et al. 2013

A&A

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Context. The way angular momentum is built up in stars during their formation process may have an impact on their further evolution. Aims. In the framework of the cold disc accretion scenario, we study how angular momentum builds up inside the star during its formation for the first time and what the consequences are for its evolution on the main sequence (MS). Methods. Computation begins from a hydrostatic core on the Hayashi line of 0.7 M at solar metallicity (Z = 0.014) rotating as a solid body. Accretion rates depending on the luminosity of the accreting object are considered, which vary between 1.5 × 10 −5 and 1.7 × 10 −3 M yr −1 . The accreted matter is assumed to have an angular velocity equal to that of the outer layer of the accreting star. Models are computed for a mass-range on the zero-age main sequence (ZAMS) between 2 and 22 M . Results. We study how the internal and surface velocities vary as a function of time during the accretion phase and the evolution towards the ZAMS. Stellar models, whose evolution has been followed along the pre-MS phase, are found to exhibit a shallow gradient of angular velocity on the ZAMS. Typically, the 6 M model has a core that rotates 50% faster than the surface on the ZAMS. The degree of differential rotation on the ZAMS decreases when the mass increases (for a fixed value of v ZAMS /v crit ). The MS evolution of our models with a pre-MS accreting phase show no significant differences with respect to those of corresponding models computed from the ZAMS with an initial solid-body rotation. Interestingly, there exists a maximum surface velocity that can be reached through the present scenario of formation for masses on the ZAMS larger than 8 M . Typically, only stars with surface velocities on the ZAMS lower than about 45% of the critical velocity can be formed for 14 M models. Reaching higher velocities would require starting from cores that rotate above the critical limit. We find that this upper velocity limit is smaller for higher masses. In contrast, there is no restriction below 8 M , and the whole domain of velocities to the critical point can be reached.

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Evolution of Massive Protostars With High Accretion Rates

Cited by 383 publications

References 58 publications

Disk-mediated accretion burst in a high-mass young stellar object

Disk-mediated accretion burst in a high-mass young stellar object

Tightening the belt: Constraining the mass and evolution in SDC335

Star formation with disc accretion and rotation

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