JWST in the Age of Time Domain Astronomy: Understanding FU Orionis - - PowerPoint PPT Presentation

JWST in the Age of Time Domain Astronomy: Understanding FU Orionis Phenomena

Joel D. Green Space Telescope Science Institute

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Dissecting the Spectrum of a Low Mass Star

Modified from Hartmann & Kenyon, 1996, ARAA, 34, 207

Mass ~ < 2 М8 X-ray UV Optical Near-IR Mid-IR Far-IR Submm Radio Millimeter

/Jet

4

HST/WFPC2; 1995-2000 (A. Watson) HH30 jet

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How does this happen?

Tightly collimated jet Quasi-periodic ejecta clumping

Episodic Accretion & Outflow?

103 yr timescale 10 yr timescale

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Disk–star interaction and the formation of a conical wind. The wind/outflow base

• riginates very close to the stellar photosphere.

Figure from Königl A et al. MNRAS 2011;416:757-766

• Accreting matter compresses the

magnetosphere of the star

• Field lines enhanced via differential

rotation between disk and star

• Conical winds & outflows twist from the

inner disk

Romanova et al., 2009, MNRAS, 399, 1802 Kurosawa and Romanova, 2012, MNRAS, 426, 2901

A Close Relationship Between Accretion and Outflow?

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Potential Triggers of Burst Behavior

• Intrinsic luminosity changes due

to disk-related instabilities

• Binarity: e.g, FU Ori (Reipurth &

Aspin, 2004, ApJ, 608, 65) – Mass transfer? Instability triggered by perturbing the disk externally?

• Variable extinction (flared disks,

periodic obscuration); Morales- Calderón et al. 2012, ApJ, 733, 50

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GI: Outer Disk: Q = csΩ / πGΣ ~ 1 MRI: Inner Disk (hot/highly ionized) Transition region: (1-10 AU) GI-MRI junction not smooth => episodic accretion Predicts correct outburst strength and timescale But the details of MRI triggering are uncertain

Armitage et al. 2001, MNRAS, 324, 705 Zhu et al. 2009, ApJ, 694, 1045 Zhu et al. 2010, ApJ, 714, 1143 Martin & Lubow 2011, AJ, 740, 6 Martin et al. 2012, MNRAS, 423, 2718 Bae et al. 2013, ApJ, 764, 141

Magnetorotational + Gravitational Instability Model (MRI+GI)

Key zone is 1-10 AU Single burst

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Empirical Prediction à New Accretion Paradigm

Hartmann 1998, Camb. Astrophys. Ser., Vol. 32 From disk fragmentation model of Vorobyov & Basu 2010, ApJ, 719, 1896

Back of napkin Simulation

Did it happen here?

Stardust mission reveals crystalline dust in comets (Brownlee et al. 2012) Depletion of certain volatiles in the inner solar system evidence of transient heating? (Hubbard & Ebel 2014)

FUors (may) anchor the fossil record of our Solar System to the protostellar development timescale

Outward transport of CAIs? Wurm & Haack (2009)

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Clustered isotopic ratios of Fe and Al (G. MacPherson, priv. comm)

EXors and FUors are a Natural Laboratory for Accretion Physics

Courtesy: R. Hurt, SSC Ábrahám et al., 2009, Nature, 459, 224

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Why study FUors and related

• utbursts?
• Represent stages wherein most of the YSO mass may be

accumulated, processed, ejected

• Accretion mechanism may differ from the classical

magnetospheric TTS accretion model: "new" accretion physics

• Diagnostic for outburst triggering mechanisms, an important

problem

• Offer "unveiled" examples of YSOs with accretion rates

comparable to embedded sources

• Can look for signs of outburst in our solar system: clustered

isotopic ratios representing system-wide events

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Rapid Changes in Optical and NIR

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Hillenbrand+19

1 10 100 Wavelength [!m] 10

10

10

10

F [W m

HBC 722

Taurus median

AV = 3.1 mag

T = 4000 K

AV = 3.1 mag

Miller et al. Kóspál et al.

Kospal+10

Key Questions

• What is the triggering mechanism of these bursts?
• What effect does a burst have on the protoplanetary

system?

• What is the connection between accretion and
• utflow?
• Are (multiple) bursts common to most protostars?
• Did it happen here in the Solar System?

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Herczeg, Calvet, & Hartmann 2016

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Processes with Potentially Observable Signatures

Green et al. 2019; 2020 Decadal Survey Whitepaper

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Disk Chemistry: Temperature and Wavelength

So all we have to do…

• Observe objects repeatedly before, during, and

after outburst

– Using tracers that provide accretion rate, temperature, kinematics, chemical pathway alterations, and radial profiles – At radio, mm, IR, optical, UV, and X-ray, including spectroscopy of R~ 100-100,000 – In tracers of gas, ice, and dust – On objects that are typically 400-4000 pc distant – Waiting for sources to go into outburst, and return to quiescence (~ 100 yr) – While rapidly surveying the sky

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Where can we progress?

• Time domain
• X-ray, MIR, FIR, submm, and radio large

sensitivity improvements

• Spatial resolution in radio, MIR, FIR
• Survey speeds, area coverage
• High spectral resolution
• Space-accessible bands

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Or in summary

• High (v < 10 km/s for survey; v < 1 km/s for

followup) spectral resolution capabilities with relatively rapid response times in the IR (3-500 μm), X-ray (0.1-10 keV), and radio (cm) are critical to follow the course of accretion and outflow during an outburst. Complementary, AU-scale radio observations are needed to probe the disk accretion zone, and 10 AU-scale to probe chemical and kinematic structures of the disk- forming regions, and track changes in the dust, ice, and gas within protostellar envelopes.

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FUors and X-rays

• FUors are X-ray bright,

compared to X-ray active T Tauri stars, but not relative to the total system output

• Multiple (hard and soft) X-ray

components sometimes seen but can be attributed to binaries?

• Chandra/XMM studies ongoing

to track emission during burst – accretion column obscuration (in prep.)? Skinner et al., AJ, 2006, 643, 995; Skinner et al. 2009, ApJ, 696, 766

Hard X-rays = magnetically-driven Soft X-rays = accretion processes

e.g. Grosso et al. 2010, A&A 522, A56

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The Burst of FUor HBC 722 –

• ptical, near-IR, and X-ray

monitoring, 2010-2013

Lee+15

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Diary of a Burst

• 2010: 400 km/s outflow/wind
• 2011-2012: luminosity & accretion rate decreases, but wind

remains strong. Hot inner disk dominated rotation profiles as central star fades.

– X-rays indicate accretion onto central star activated

• 2013-14: Disk heat moves outward (viscous dissipation?) as profiles

narrow (IGRINS).

– X-rays indicate large column of dust-depleted absorbing material

• Outer disks affected on longer timescales (years)
• Envelope chemistry, ice composition are affected (years to

decades…) if envelopes are still present

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How does line emission evolve during the burst, and what is it tracing? How does the disk change during a burst?

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FUor silicate dust is amorphous 50-90% of T Tauri stars show crystalline features

Amorphous silicate emission Water vapor (abs) – disk photosphere? Green+06

Spitzer

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Ábraham et al., 2009, Nature, 459, 224

IR Spectroscopy Traces Rapid Changes in Dust and Gas

Does dust processing from flash heating (or vertical transport and stirring of dust grains)

• ccur on few month timescales?

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FU Orionis in Outburst

circa 2004 circa 2016 Green+16c Green+06 Black model = Red model x 0.88 Spitzer-IRS 2004 SOFIA- FORCAST 2016

• 12%

% Change 2004-16:

• 7%

<=7% Overall uncertainty ~ 4.2%

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Silicates

No change in solid state features

H2O?

Dust Hot gas Green+16c Green+06

H2O?

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Depletion of the innermost disk regions? Cooling?

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Next up, V1057 Cyg!

JWST-MIRI and NIRSpec can track FUors during burst

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Multi-wavelength Analysis

Chandra/Swift ToO and Monitoring – Liebhart+14, Pooley+18 ALMA, Herschel – e.g. Green+13,16, Cieza+16, Hales+16, Lee+18; Johnstone+16, Molyarova+18 VLTI/MIDI, Spitzer, JWST, SphereX – e.g. Kospal+18, Green+16

Optical/IR Monitoring: e.g., Hillenbrand+18,+19; Fischer+19 New transient surveys (PTF, LSST; WFIRST, Euclid) will provide “early warning” with more systematics

SOFIA/HIRMES; Origins Space Telescope; e.g., Logan+19