Massive Compact Disks around FU Orionis–type Young Eruptive Stars Revealed by ALMA

Kóspál, Á.; Miera, Fernando Cruz-Sáenz de; White, Jacob Aaron; Ábrahám, P.; Chen, L.; Csengeri, T.; Dong, Ruobing; Dunham, Michael M.; Fehér, Orsolya; Green, Joel D.; Hashimoto, Jun; Henning, Th.; Hogerheijde, M. R.; Kudo, Tomoyuki; Liu, Hauyu Baobab; Miki, Takami; Vorobyov, Eduard I.

doi:10.3847/1538-4365/ac0f09

“…These FUors and YSOs span a large region in the mid-IR CMD (Figure 16). While a considerable range of extinctions enables the model curves to cover the data adequately, some FUors are brighter and redder than predicted here (e.g., the three upper-right FUors V883 Ori, HBC 494, and V346 Nor; Ruíz-Rodríguez et al 2017a, 2017bKóspál et al 2021). Individual considerations are needed to account for the redness: V883 Ori exhibits a singular brightness in the W 2 band presumably due to saturation bias or line emission (Section 4.2.2), while a smooth rise in the WISE fluxes of V346 Nor from the W 1 band to W 3 band at 11.6 μm implies warm continuum emission or very heavy extinction.…”

Section: Outbursts In the Mid-irmentioning

confidence: 60%

Diagnosing FU Ori-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-infrared

Liu

¹

,

Herczeg

²

,

Johnstone

³

et al. 2022

ApJ

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FU Ori-type objects (FUors) are decades-long outbursts of accretion onto young stars that are strong enough to viscously heat disks so that the disk outshines the central star. We construct models for FUor objects by calculating emission components from a steady-state viscous accretion disk, a passively-heated dusty disk, magnetospheric accretion columns, and the stellar photosphere. We explore the parameter space of the accretion rate M ̇ and stellar mass M * to investigate implications on the optical and near-infrared spectral energy distribution and spectral lines. The models are validated by fitting to multiwavelength photometry of three confirmed FUor objects, FU Ori, V883 Ori, and HBC 722, and then comparing the predicted spectra to the observed optical and infrared spectra. The brightness ratio between the viscous disk and the stellar photosphere, η, provides an important guide for identifying viscous accretion disks, with η = 1 (“transition line”) and η = 5 (“sufficient dominance line”) marking turning points in diagnostics, evaluated here in the near-infrared. These turning points indicate the emergence and complete development of FUor-characteristic strong CO absorption, weak metallic absorption, the triangular spectral continuum shape in the H band, and location in color–magnitude diagrams. Lower M * and higher M ̇ imply larger η; for M * = 0.3 M ⊙, η = 1 corresponds to M ̇ = 2 × 10 − 7 M ⊙ yr−1 and η = 5 to M ̇ = 6 × 10 − 7 M ⊙ yr−1. The “sufficient dominance line” also coincides with the expected accretion rate where accreting material directly reaches the star. We discuss implications of the models on extinction diagnostics, FUor brightening timescales, viscous disks during initial protostellar growth, and eruptive young stellar objects associated with FUors.

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“…For a typical gas-to-dust ratio of 100, similar to the interstellar medium value, we obtain a lower limit for the total disk mass (gas and dust) of ∼0.02 M . FU Ori's disk is therefore still one of the most compact and least massive in its class (Liu et al 2018;Kóspál et al 2021).…”

Section: Disk Massmentioning

confidence: 99%

The disk of FU Orionis viewed with MATISSE/VLTI

Lykou

¹

,

Ábrahám

²

,

Chen

³

et al. 2022

A&A

Self Cite

11

1

0

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Aims. We studied the accretion disk of the archetypal eruptive young star FU Orionis with the use of mid-infrared interferometry, which enabled us to resolve the innermost regions of the disk down to a spatial resolution of 3 milliarcseconds (mas) in the L band, that is, within 1 au of the protostar. Methods. We used the interferometric instrument MATISSE/VLTI to obtain observations of FU Ori’s disk in the L, M, and N bands with multiple baseline configurations. We also obtained contemporaneous photometry in the optical (UBVRIr′i′; SAAO and Konkoly Observatory) and near-infrared (JHKs; NOT). Our results were compared with radiative transfer simulations modeled by RADMC-3D. Results. The disk of FU Orionis is marginally resolved with MATISSE, suggesting that the region emitting in the thermal infrared is rather compact. An upper limit of ~1.3 ± 0.1 mas (in L) can be given for the diameter of the disk region probed in the L band, corresponding to 0.5 au at the adopted Gaia EDR3 distance. This represents the hot, gaseous region of the accretion disk. The N-band data indicate that the dusty passive disk is silicate-rich. Only the innermost region of said dusty disk is found to emit strongly in the N band, and it is resolved at an angular size of ~5 mas, which translates to a diameter of about 2 au. The observations therefore place stringent constraints for the outer radius of the inner accretion disk. Dust radiative transfer simulations with RADMC-3D provide adequate fits to the spectral energy distribution from the optical to the submillimeter and to the interferometric observables when opting for an accretion rate M ~ 2 × 10−5 M⊙ yr−1 and assuming M* = 0.6 M⊙, Most importantly, the hot inner accretion disk’s outer radius can be fixed at 0.3 au. The outer radius of the dusty disk is placed at 100 au, based on constraints from scattered-light images in the literature. The dust mass contained in the disk is 2.4 × 10−4 M⊙, and for a typical gas-to-dust ratio of 100, the total mass in the disk is approximately 0.02 M⊙. We did not find any evidence for a nearby companion in the current interferometric data, and we tentatively explored the case of disk misalignment. For the latter, our modeling results suggest that the disk orientation is similar to that found in previous imaging studies by ALMA. Should there be an asymmetry in the very compact, inner accretion disk, this might be resolved at even smaller spatial scales (≤1 mas).

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“…ALMA observations of FU Ori revealed direct evidence for binary interactions (Zurlo et al 2017;Cieza et al 2018;Pérez et al 2020;Kóspál et al 2021). In particular, CO line observations have revealed distinct blue and red shifted velocities corresponding to expanding 'shells or rings'.…”

Section: Discussionmentioning

confidence: 99%

On the rise times in FU Orionis events

Borchert,

Price,

Pinte

et al. 2021

Preprint

0

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We examine whether stellar flyby simulations can initiate FU Orionis outbursts using 3D hydrodynamics simulations coupled to live Monte Carlo radiative transfer. We find that a flyby where the secondary penetrates the circumprimary disc triggers a 1-2 year rise in the mass accretion rate to 10 −4 M yr −1 that remains high ( 10 −5 M yr −1 ) for more than a hundred years, similar to the outburst observed in FU Ori. Importantly, we find that the less massive star becomes the dominant accretor, as observed.

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Massive Compact Disks around FU Orionis–type Young Eruptive Stars Revealed by ALMA

Cited by 31 publications

References 114 publications

Diagnosing FU Ori-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-infrared

Diagnosing FU Ori-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-infrared

The disk of FU Orionis viewed with MATISSE/VLTI

On the rise times in FU Orionis events

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