Determining the recurrence time-scale of long-lasting YSO outbursts

Peña, C. Contreras; Naylor, T.; Morrell, Sam

doi:10.1093/mnras/stz1019

Cited by 50 publications

(20 citation statements)

References 160 publications

(194 reference statements)

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“…This is similar to what is inferred from observations (e.g. Scholz et al 2013;Hillenbrand & Findeisen 2015;Fischer et al 2019) (see also Peña et al 2019, for longer outburst timescale estimates for older, Class I/II, YSOs). It is assumed that in the quiescent phase gas accretes onto the protostar at a rate oḟ M = 10 −6 M yr −1 (this is a free parameter in our calculation) and the protostellar luminosity is then on the order of ∼ 1 L .…”

Section: Radiation Hydrodynamic Simulationssupporting

confidence: 90%

Observational signatures of outbursting protostars - I: From hydrodynamic simulations to observations

MacFarlane

Stamatellos

Johnstone

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Accretion onto protostars may occur in sharp bursts. Accretion bursts during the embedded phase of young protostars are probably most intense, but can only be inferred indirectly through long-wavelength observations. We perform radiative transfer calculations for young stellar objects (YSOs) formed in hydrodynamic simulations to predict the long wavelength, sub-mm and mm, flux responses to episodic accretion events, taking into account heating from the young protostar and from the interstellar radiation field. We find that the flux increase due to episodic accretion events is more prominent at sub-mm wavelengths than at mm wavelengths; e.g. a factor of ∼ 570 increase in the luminosity of the young protostar leads to a flux increase of a factor of 47 at 250 µm but only a factor of 10 at 1.3 mm. Heating from the interstellar radiation field may reduce further the flux increase observed at longer wavelengths. We find that during FU Ori-type outbursts the bolometric temperature and luminosity may incorrectly classify a source as a more evolved YSO, due to a larger fraction of the radiation of the object being emitted at shorter wavelengths.

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Section: Radiation Hydrodynamic Simulationssupporting

confidence: 90%

Observational signatures of outbursting protostars - I: From hydrodynamic simulations to observations

MacFarlane

Stamatellos

Johnstone

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…X-ray surveys of nearby star-forming regions (d < 3 kpc) have identified tens of thousands of YSOs, and there are likely hundreds of thousands of YSOs projected in these fields that have not been detected (Feigelson 2018). If the outburst rate were ∼10 −5 yr −1 , as suggested by Contreras Peña et al (2019), at least one outburst is likely in this sample of stars during the next decade, allowing constraints on pre-outburst X-ray luminosity to be determined.…”

Section: Discussionmentioning

confidence: 69%

A Comparison of the X-Ray Properties of FU Ori-type Stars to Generic Young Stellar Objects

Kuhn

Hillenbrand

2019

ApJ

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Like other young stellar objects (YSOs), FU Ori-type stars have been detected as strong X-ray emitters. However, little is known about how the outbursts of these stars affect their X-ray properties. We assemble available X-ray data from XMM Newton and Chandra observations of 16 FU Ori stars, including a new XMM Newton observation of Gaia 17bpi during its optical rise phase. Of these stars, six were detected at least once, while 10 were non-detections, for which we calculate upper limits on intrinsic X-ray luminosity (L X ) as a function of plasma temperature (kT ) and column density (N H ). The detected FU Ori stars tend to be more X-ray luminous than typical for non-outbursting YSOs, based on comparison to a sample of low-mass stars in the Orion Nebula Cluster. FU Ori stars with high L X have been observed both at the onset of their outbursts and decades later. We use the Kaplan-Meier estimator to investigate whether the higher X-ray luminosities for FU Ori stars is characteristic or a result of selection effects, and we find the difference to be statistically significant (p < 0.01) even when non-detections are taken into account. The additional X-ray luminosity of FU Ori stars relative to non-outbursting YSOs cannot be explained by accretion shocks, given the high observed plasma temperatures. This suggests that, for many FU Ori stars, either 1) the outburst leads to a restructuring of the magnetosphere in a way that enhances X-ray emission, or 2) FU Ori outbursts are more likely to occur among YSOs with the highest quiescent X-ray luminosity.

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“…Most of these effects appreciably depend on the magnitude, duration, and frequency of the bursts that may occur in the early evolution of a young stellar object. While the burst magnitude can be estimated from multi-waveband observations, the burst duration and frequency is difficult to derive observationally because of the long timescales of the bursts, although attempts were made to infer them from the known statistics of the bursts (Scholz et al 2013;Hillenbrand & Findeisen 2015;Contreras Peña et al 2019;Fischer et al 2019). Alternatively, the burst characteristics can be estimated from known numerical models (e.g., Vorobyov & Basu 2015), which motivates further investigations as to the nature of the burst phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Accretion bursts in magnetized gas-dust protoplanetary disks

Vorobyov

Khaibrakhmanov

Basu

et al. 2020

A&A

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Aims. Accretion bursts triggered by the magnetorotational instability (MRI) in the innermost disk regions were studied for protoplanetary gas-dust disks that formed from prestellar cores of a various mass Mcore and mass-to-magnetic flux ratio λ. Methods. Numerical magnetohydrodynamics simulations in the thin-disk limit were employed to study the long-term (~1.0 Myr) evolution of protoplanetary disks with an adaptive turbulent α-parameter, which explicitly depends on the strength of the magnetic field and ionization fraction in the disk. The numerical models also feature the co-evolution of gas and dust, including the back-reaction of dust on gas and dust growth. Results. A dead zone with a low ionization fraction of x≲10−13 and temperature on the order of several hundred Kelvin forms in the inner disk soon after its formation, extending from several to several tens of astronomical units depending on the model. The dead zone features pronounced dust rings that are formed due to the concentration of grown dust particles in the local pressure maxima. Thermal ionization of alkaline metals in the dead zone trigger the MRI and associated accretion burst, which is characterized by a sharp rise, small-scale variability in the active phase, and fast decline once the inner MRI-active region is depleted of matter. The burst occurrence frequency is highest in the initial stages of disk formation and is driven by gravitational instability (GI), but it declines with diminishing disk mass-loading from the infalling envelope. There is a causal link between the initial burst activity and the strength of GI in the disk fueled by mass infall from the envelope. We find that the MRI-driven burst phenomenon occurs for λ = 2–10, but diminishes in models with Mcore ≲ M⊙, suggesting a lower limit on the stellar mass for which the MRI-triggered burst can occur. Conclusions. The MRI-triggered bursts occur for a wide range of mass-to-magnetic flux ratios and initial cloud core masses. The burst occurrence frequency is highest in the initial disk formation stage and reduces as the disk evolves from a gravitationally unstable to a viscous-dominated state. The MRI-triggered bursts are intrinsically connected with the dust rings in the inner disk regions, and both can be a manifestation of the same phenomenon, that is to say the formation of a dead zone.

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Determining the recurrence time-scale of long-lasting YSO outbursts

Cited by 50 publications

References 160 publications

Observational signatures of outbursting protostars - I: From hydrodynamic simulations to observations

Observational signatures of outbursting protostars - I: From hydrodynamic simulations to observations

A Comparison of the X-Ray Properties of FU Ori-type Stars to Generic Young Stellar Objects

Accretion bursts in magnetized gas-dust protoplanetary disks

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