YSOVAR: The Young Stellar Object Variability Project

Ann Marie CodySpitzer/IPAC, Caltech

YSOVAR: “WHY-SO-VARiable?”

Ann Marie CodySpitzer/IPAC, Caltech

Thanks to many collaborators…

John Stauffer (P.I.), Maria Morales-Calderón

At Caltech, JPL & LA: Luisa Rebull, Lynne Hillenbrand, John Carpenter, Peter Plavchan, Krzysztof Findeisen, Neal Turner, Susan Terebey

And many other institutions:The YSOVAR team: ysovar.ipac.caltech.edu

outline

Motivation: Why do yet another photometric monitoring campaign?

What is YSOVAR?

First results from YSOVAR

A brief foray into NGC 2264

outline

Motivation: Why do yet another photometric monitoring campaign?

What is YSOVAR?

First results from YSOVAR

A brief foray into NGC 2264

Hartmann 1999

Static, symmetric

picture

Young stars are dynamic!

HH30:HST/WFPC2 @ ~1 frame per year disk diameter ~ 450 AULight beam P~7.5d

(Duran-Rojas et al. 2009; Watson & Stapelfeldt 2007)

Periodic- Stassun et al. 1999 Aperiodic- Frasca et al. (2010)

80 days 80 days

We can learn about dynamics through time series photometry

?

MOSTCoRoT

Spitzer

Alencar et al. (2010) Morales-Calderón et al. (2009)

2003-2013: A revolution in space based Monitoring of young stars

Optical infrared

outline

Motivation: Why do yet another photometric monitoring campaign?

What is YSOVAR?

First results from YSOVAR

A brief foray into NGC 2264

Ysovar in a nutshell

GO-6 Exploration Science program >500 hrs of Spitzer time

Time series photometric monitoring at 3.6 and 4.5 um

Includes ~1 square degree of the ONC plus 11 other well-known SFRs

Typically ~100 epochs/region (sampled ~2x/day for 40d, less frequently at longer timescales)

A couple thousand YSOs with good light curves!

Data taken over the period Sep 2009 -- June 2011

Ysovar in a nutshell

YSOVAR

Time series

L1688 Serpens Main Serpens South IRAS 20050+2070 IC1396 Ceph-C AFGL 490 NCG 1333 Orion Mon R2 GGD 12-15 NGC 2264

Ysovar clusters

~250 hours of observing time ~ 1 square degree region of the Orion Nebula cluster Cadence: 40 days, with 2 ∼epochs each day.~1400 Class I and II Orion YSOs with good quality time series (1-2% accuracy)

Ysovar/Orion spitzer data

Near-IR:• CFHT/WIRCAM: 10 nights. J & Ks• UKIRT/WFCAM: ~30 epochs over 60 nights. J• 2.1m KPNO/FLAMINGOS: 10 nights. JHKs• CTIO 1.3/ANDICAM: ~30 epochs over 60 nights. J & I • PAIRITEL: ~20 epochs over 35 nights. JHKs • CAIN/TCS: 15 nights. J & Ks

Optical:• USNO/Flagstaff: 7 nights. I band• LOWELL/21”: 22 nights. I band• NMSU-APO/40”: 24 nights. VI bands• LCOGT/FTEM: 17 nights. I band.• KPNO 24”/Slotis: 27 nights. I band• CAHA 1.23m: 30 nights. BVI• Arcsat APO, 0.5m: 5 nights. I band

Ysovar/Orion Ground-based data

Ysovar science goals

• Provide empirical constraints on physical processes and structures characterizing the interaction between the star, inner disk/envelope and accretion flows.

• Make unique measurements of the rotational periods of the most embedded, youngest protostars

• Place constraints on the long-term variability of YSOs at IRAC wavelengths.

• Discover new eclipsing binary systems to provide benchmarks for young, low-mass evolution tracks

Light curveacquisition

Morphologicalclassification

Search for correlations with stellar/disk parameters

Comparison with models

Rotational evolution Disk structure Magnetospheric accretion

outline

Motivation: Why do yet another photometric monitoring campaign?

What is YSOVAR?

First results from YSOVAR

A brief foray into NGC 2264

An enormous variety of light curves!

First results

Morales-Calderón et al. (2011)

Spitzer light curves: 3.6 and 4.5 μm

Ysovar/Orion Variability examples

Combined Spitzer and ground-based light curvesMorales-Calderón et al.

(2011)

Ysovar/Orion Variability examples

Ysovar/Orion Variability census

70% of disk bearing stars are variable in the IRAC bands

“Orion christmas tree”

Light curveacquisition

Search for correlations with stellar/disk parameters

Comparison with models

Rotational evolution Disk structure Magnetospheric accretion

Morphologicalclassification

• Can get a period for just 16% of the variable Class I+IIs (90% of those are Class IIs, 10% are Class Is.)

mostly seeing disks here

• For members w/o IR excess, 30% are variables, mostly periodic photosphere

• 30% of sample had literature period; 35% of those are recovered, just 18% of those with IR excess (thermal dust emission on top of stellar signal).

• 137 new periods.

Periodic stars

Periodic starsTests of disk locking

YSOVAR: everything but Orion YSOVAR: everything including Orion

Disk bearing

Bare photospheres

courtesy L. Rebull

6 new eclipsing binaries in orion

SpTs:K0,K2

SpTs:M5,M6

ISOY J0535-0447P=3.906dM1=0.83M1=0.05

θ1 Ori EM1=2.807M2=2.797

Morales-Calderón et al. (2012)

41 examples in the Orion data.

Flux dips ~0.1-0.4 mag IRAC up to >1 mag at I

and J <3 days duration

Usually one or two dips in 40 days

Extincting bodies?

“dippers”: Aa tau analogs

• Disk must be seen at relatively high (and relatively narrow range of) inclinations to do this, so expect that they are rare.

• YSOVAR Orion (year 1): Morales-Calderon et al. (2011) finds overall fraction likely ~5% (2011).

• First CoRoT short run (2008) on NGC2264: Alencar et al. (2010) finds overall fraction likely ~30%.

• What’s going on? Different ages of stars (Orion vs. NGC 2264)? Different wavelengths (optical vs. IR)? Different cadences? (Different definitions of the category?)

Questions about dippers

IJ [3.6]

[4.5]

Large amplitude infrared behavior

No variations at shorter wavelengths.

Warped disks?

outline

Motivation: Why do yet another photometric monitoring campaign?

What is YSOVAR?

First results from YSOVAR

A brief foray into NGC 2264

Ysovar’s successor: the Coordinated Synoptic Investigation

of NGC 2264

Spitzer: 30 days, 3.6-4.5 μm CoRoT: 40 days, optical Chandra/ACIS: 300ks (3.5 days) MOST: 40 days, optical VLT/Flames: ~20 epochs Ground-based monitoring U-K bands: ~3 months

CSI results: many pairs of optical and ir lightcurves are uncorrelated!

CoRoT SpitzerMag

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Mag

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Time (days)

40 days

CoRoT Spitzer

CSI results: optical/ir phase lags are rare

CoRoT Spitzer

At least 10% of disk-bearing stars showHigh-amplitude behavior in the ir only

CoRoT Spitzer

Mag

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CoRoT Spitzer

Mag

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High inclination:Quasi-periodic flux dips caused by disk blobs or

warps

Corot data reveals Flux events that may be accretion bursts

These objects have preferentially high UV excesses and Hα emission indicative of strong accretion.

Light curveacquisition

Non-variable ~17%

Search for correlations with stellar/disk parameters

Comparison with models

Periodic, AA Tau~11%

Aperiodic, dipper~13%

Aperiodic, stochastic

~26%

Aperiodic, burster~11%

Periodic, sinusoidal

~3% Non-variable optical/

variable IR~10%

Periodic, non-

sinusoidal~12%

Disk-bearing stars

Stochasticstars

Quasi-periodicstars

Purelyperiodic

Flux Asymmetry

Stochasticity

An approach to classification

Eclipsingbinaries

Bursters

Dippers

classes can now be selected statistically!

Cody, Stauffer, in prep.

Summary and future plans We have performed a periodic variability census in the Orion dataset;complete classification and understanding of aperiodic behavior remains

Among the prominent variability types are “dippers” and high amplitude infrared behavior…along with 6 new eclipsing binaries

We find evidence for disk locking in all clusters

We have just finished a complete morphological classification of variability in NGC 2264 with CoRoT and Spitzer; we will now go back to Orion and apply this framework

Follow-up of interesting variables is upcoming; the long time baseline available is another direction to pursue

Stay tuned for further results from the full set of YSOVAR clusters and the CSI project

You can download YSOVAR Orion data from:

http://ysovar.ipac.caltech.edu/first_data_release.htmlhttp://cosmos.physast.uga.edu/Public/

First data release

Miscellaneous slides

Ke et al. (2012)

Inner rim scale height changes

No magnetic support Neal Turner, JPL

V J

3.6

60o

0.8 AU

Magnetic support near 0.1 AU

V J

3.6

60o

0.8 AU

… Enter csi 2264

CoRoT Spitzer

CoRoT Spitzer

Mag

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40 days

Time (days)

Fading events become deeper in the infrared as we go to lower mass…

CoRoT Spitzer

disk-bearing stars:Unexplained Periodic behavior

CoRoT Spitzer

Spitzer

…And some objects are just plain bizarre!

CoRoT Spitzer

Mag

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Disk scale height changes (due to x-ray ionization or magnetic turbuluence)

Heating by stellar hotspots, followed by dust sublimation or IR re-emission

Disk asymmetries (warps, overdensities) causing occultation events or bright/dark spots

Need simultaneous monitoring at multiple Wavelengths to assess these models

Other possibilities for infrared variability mechanisms

Corot data reveals Flux events that may be accretion bursts

Stauffer, Cody, in prep.

These objects have preferentially high UV excesses and Hα emission indicative of strong accretion.

Mag

nitu

de

Time (days)

MOST enigmatic target: HD 31305

P=2.94 d

The combination of periodic variability plus stochastic residuals is highly suggestive of a young star- but unheard of for such an early spectral type!

Cody et al. (2013)

A new type of young A star variability?

Light curveacquisition

Non-variable

Search for correlations with stellar/disk parameters

Periodic Aperiodic

Starspots Disk processes

su aurigae: mysterious periodicity observed with most

•Light curve behavior that appears periodic– but not perfectly •Periodicity is too long to be consistent with the spectroscopic rotation velocity, vsini disk-related variability? P 0.05 AU•Previous studies would not have separated this phenomenon from stellar spot-dominated light curves•Further evidence for periodic variability originating in disks was recently published by Artemenko et al. (2013)

Cody & Hillenbrand (2013)

P=2.66 d

Light curveacquisition

Non-variable

Search for correlations with stellar/disk parameters

Periodic Aperiodic

Starspots Disk processes