YSOVAR: The Young Stellar Object Variability Project Ann Marie Cody Spitzer/IPAC, Caltech

YSOVAR: “WHY-SO-VAR iable ?” Ann Marie Cody Spitzer/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

Young stars are dynamic! HH30: ~1 frame per year disk diameter ~ 450 AU Light beam P~7.5d (Duran-Rojas et al. 2009; Watson & Stapelfeldt 2007)

Periodic- Stassun et al Aperiodic- Frasca et al. (2010)  80 days  We can learn about dynamics through time series photometry

? MOST CoRoT Spitzer Alencar et al. (2010) Morales-Calderón et al. (2009) : A revolution in space based Monitoring of young stars Opticalinfrared

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 June 2011

Ysovar in a nutshell Time series

L1688 Serpens Main Serpens South IRAS IC1396 Ceph-C AFGL 490 NCG 1333 Orion Mon R2 GGD 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 curve acquisition Light curve acquisition Morphological classification Morphological classification 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 curves Morales-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 curve acquisition Light curve acquisition Search for correlations with stellar/disk parameters Comparison with models  Rotational evolution  Disk structure  Magnetospheric accretion Morphological classification Morphological classification

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

Tests of disk locking YSOVAR: everything but OrionYSOVAR: everything including Orion Disk bearing Bare photospheres courtesy L. Rebull

6 new eclipsing binaries in orion SpTs: K0,K2 SpTs: M5,M6 ISOY J P=3.906d M 1 =0.83 M 1 =0.05 θ 1 Ori E M 1 =2.807 M 2 =2.797 Morales-Calderón et al. (2012)

 41 examples in the Orion data.  Flux dips ~ 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

I J [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, 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  Spitzer Magnitude [4.5] Time (days) 40 days  CoRoT  Spitzer

CSI results: optical/ir phase lags are rare  CoRoT  Spitzer

At least 10% of disk-bearing stars show High-amplitude behavior in the ir only  CoRoT  Spitzer Magnitude [4.5] Time (days)

 CoRoT  Spitzer Magnitude [4.5] Time (days) 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 curve acquisition Light curve acquisition Non- variable ~17% Search for correlations with stellar/disk parameters Comparison with models Periodic, AA Tau ~11% Periodic, AA Tau ~11% Aperiodic, dipper ~13% Aperiodic, dipper ~13% Aperiodic, stochastic ~26% Aperiodic, stochastic ~26% Aperiodic, burster ~11% Aperiodic, burster ~11% Periodic, sinusoidal ~3% Periodic, sinusoidal ~3% Non-variable optical/ variable IR ~10% Non-variable optical/ variable IR ~10% Periodic, non- sinusoidal ~12% Periodic, non- sinusoidal ~12% Disk-bearing stars

Stochastic stars Quasi-periodic stars Purely periodic Flux Asymmetry Stochasticity An approach to classification Eclipsing binaries 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: First data release

Miscellaneous slides

Ke et al. (2012) Inner rim scale height changes

No magnetic support Neal Turner, JPL V J o 0.8 AU

Magnetic support near 0.1 AU V J o 0.8 AU

… Enter csi 2264  CoRoT  Spitzer Magnitude [4.5] 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 Magnitude [4.5] Time (days)

 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. Magnitude Time (days)

MOST enigmatic target: HD 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 curve acquisition Light curve acquisition 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 curve acquisition Light curve acquisition Non-variable Search for correlations with stellar/disk parameters Periodic Aperiodic Starspots Disk processes