The evolution of protostars. I - Global formulation and results

Stahler, Steven W.; Shu, Frank H.; Taam, R. E.

doi:10.1086/158377

Cited by 340 publications

(230 citation statements)

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“…If we assume R Ã ¼ 4 R (Stahler et al 1980) L acc is estimated to be $1600 L with ourṀ value and to be $390 L with theṀ value by Schöier et al (2002). These values are much higher than the bolometric luminosity of I16293 (=27 L ; Walker et al 1986), so that the socalled ''luminosity problem'' (Kenyon et al 1990) discussed by Ohashi et al (1996) and Saito et al (1996) for L1551 IRS 5 also exists in I16293.…”

Section: Origin Of the Different Velocity Structuresmentioning

confidence: 65%

Arcsecond‐Resolution Submillimeter HCN Imaging of the Binary Protostar IRAS 16293−2422

Takakuwa¹,

Ohashi²,

Bourke³

et al. 2007

ApJ

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With the Submillimeter Array (SMA) we have made high angular resolution ($1 00 ¼ 160 AU ) observations of the protobinary system IRAS 16293À2422 in the HCN (4Y3), HC 15 N (4Y3), and 354.5 GHz continuum emission. The HCN (4Y3) line was also observed using the JCMT to supply missing short-spacing information. The submillimeter continuum emission is detected from the individual binary components of source A in the southeast and source B in the northwest, with a separation of $5 00 . The optically thin HC 15 N (4Y3) emission taken with the SMA has revealed a compact ($500 AU ) flattened structure (P:A: ¼ À16 ) at source A. This compact structure shows a velocity gradient along the projected minor axis, which can be interpreted as an infalling gas motion. Our HCN image including the short-spacing information shows an extended ($3000 AU ) circumbinary envelope, as well as the compact structure at source A. A toy model consisting of a flattened structure with radial infall toward a 1 M central star reproduces the HCN/ HC 15 N position-velocity diagram along the minor axis of the HC 15 N emission. In the extended envelope there is also a northeast (blue) to southwest (red) velocity gradient across the binary alignment, which is likely to reflect gas motion in the swept-up dense gas associated with the molecular outflow from source A. Only a weak and narrow ($2 km s À1 ) compact HC 15 N emission is associated with source B, where no clear molecular outflow is identified, suggesting the different evolutionary starges between sources A and B. Our study demonstrates the importance of adding short-spacing data to interferometer data in order to probe the detailed structure and kinematics of low-mass protostellar envelopes.

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Section: Origin Of the Different Velocity Structuresmentioning

confidence: 65%

Arcsecond‐Resolution Submillimeter HCN Imaging of the Binary Protostar IRAS 16293−2422

Takakuwa¹,

Ohashi²,

Bourke³

et al. 2007

ApJ

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“…This represents the dust border (see e.g. Stahler et al 1980), but only the radiative flux is strongly affected at that location; the hydrodynamical quantities seem relatively insensitive to the presence of this border, except for a small kink visible in the temperature profile. The second burst in radiative flux occurs at the second core border where the sharp jump in gas and radiative temperature provoke a rise in radiative flux.…”

Section: Radial Profilesmentioning

confidence: 99%

“…over a very large range of spatial scales (Larson 1969;Stahler et al 1980;Masunaga et al 1998). The collapsing material is initially optically thin to the thermal emission from the cold gas and dust grains and all the energy gained from compressional heating is transported away by the escaping radiation, which causes the cloud to collapse isothermally in the initial stages of the formation of a protostar.…”

Section: Introductionmentioning

confidence: 99%

Simulations of protostellar collapse using multigroup radiation hydrodynamics

Vaytet

Chabrier

Audit

et al. 2013

A&A

111

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Context. Star formation begins with the gravitational collapse of a dense core inside a molecular cloud. As the collapse progresses, the centre of the core begins to heat up as it becomes optically thick. The temperature and density in the centre eventually reach high enough values where fusion reactions can ignite, and the protostar is born. This sequence of events entails many physical processes, of which radiative transfer is of paramount importance. Simulated collapsing cores without radiative transfer rapidly become thermally supported before reaching high enough temperatures and densities, preventing the formation of stars. Aims. Many simulations of protostellar collapse make use of a grey treatment of radiative transfer coupled to the hydrodynamics. However, interstellar gas and dust opacities present large variations as a function of frequency, which can potentially be overlooked by grey models and lead to significantly different results. In this paper, we follow up on a previous paper on the collapse and formation of Larson's first core using multigroup radiation hydrodynamics (Paper I) by extending the calculations to the second phase of the collapse and the formation of Larson's second core. Methods. We have made the use of a non-ideal gas equation of state as well as an extensive set of spectral opacities in a spherically symmetric fully implicit Godunov code to model all the phases of the collapse of a 0.1, 1, and 10 M cloud cores. Results. We find that, for an identical central density, there are only small differences between the grey and multigroup simulations. The first core accretion shock remains supercritical while the shock at the second core border is found to be strongly subcritical with all the accreted energy being transfered to the core. The size of the first core was found to vary somewhat in the different simulations (more unstable clouds form smaller first cores) while the size, mass, and temperature of the second cores are independent of initial cloud mass, size, and temperature. Conclusions. Our simulations support the idea of a standard (universal) initial second core size of ∼3 × 10 −3 AU and mass ∼1.4 × 10 −3 M . The grey approximation for radiative transfer appears to perform well in one-dimensional simulations of protostellar collapse, most probably because of the high optical thickness of the majority of the protostar-envelope system. A simple estimate of the characteristic timescale of the second core suggests that the effects of using multigroup radiative transfer may be more important in the long-term evolution of the protostar.

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“…The rest is ejected to infinity. This is the star formation scenario through accretion (Shu 1977;Stahler et al 1980aStahler et al ,b, 1986b.…”

Section: Introductionmentioning

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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The evolution of protostars. I - Global formulation and results

Cited by 340 publications

References 0 publications

Arcsecond‐Resolution Submillimeter HCN Imaging of the Binary Protostar IRAS 16293−2422

Arcsecond‐Resolution Submillimeter HCN Imaging of the Binary Protostar IRAS 16293−2422

Simulations of protostellar collapse using multigroup radiation hydrodynamics

Star formation with disc accretion and rotation

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