YSOVAR: The Young Stellar Object Variability Project

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

YSOVAR: “WHY-SO-VARiable?” 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

Static, symmetric picture Hartmann 1999

Young stars are dynamic! HH30: HST/WFPC2 @ ~1 frame per year disk diameter ~ 450 AU Light beam P~7.5d (Duran-Rojas et al. 2009; Watson & Stapelfeldt 2007)

We can learn about dynamics through time series photometry  80 days   80 days  Periodic- Stassun et al. 1999 Aperiodic- Frasca et al. (2010)

2003-2013: A revolution in space based Monitoring of young stars Spitzer CoRoT MOST ? Alencar et al. (2010) Optical infrared Morales-Calderón et al. (2009)

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 Time series YSOVAR

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

Ysovar/Orion spitzer data • ~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 Ground-based 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 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 Morphological classification Search for correlations with stellar/disk parameters • Rotational evolution • Disk structure • Magnetospheric accretion Comparison with models

First results An enormous variety of light curves!

Ysovar/Orion Variability examples Spitzer light curves: 3.6 and 4.5 μm Morales-Calderón et al. (2011)

Ysovar/Orion Variability examples Combined Spitzer and ground-based light curves Morales-Calderón et al. (2011)

Ysovar/Orion Variability census  70% of disk bearing stars are variable in the IRAC bands

“Orion christmas tree”

Light curve acquisition Morphological classification Search for correlations with stellar/disk parameters • Rotational evolution • Disk structure • Magnetospheric accretion Comparison with models

Periodic stars • 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 Orion YSOVAR: everything including Orion Disk bearing Bare photospheres courtesy L. Rebull

6 new eclipsing binaries in orion ISOY J0535- 0447 P=3.906d M1=0.83 M1=0.05 SpTs: K0,K2 θ1Ori E M1=2.807 M2=2.797 SpTs: M5,M6 Morales-Calderón et al. (2012)

“dippers”: Aa tau analogs • 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?

Questions about dippers • 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?)

Large amplitude infrared behavior • No variations at shorter wavelengths. • Warped disks? [4.5] I [3.6] J

Ysovar’s successor: the CoordinatedSynoptic 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 irlightcurves are uncorrelated! Magnitude [4.5] CoRoTSpitzer Time (days) Magnitude [4.5] CoRoTSpitzer 40 days

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 Magnitude [4.5] CoRoTSpitzer Magnitude [4.5] Time (days)

High inclination: Quasi-periodic flux dips caused by disk blobs or warps CoRoTSpitzer Magnitude [4.5] Time (days)

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 Disk-bearing stars Periodic, AA Tau ~11% Aperiodic, stochastic ~26% Periodic, sinusoidal ~3% Aperiodic, dipper ~13% Non-variable optical/ variable IR ~10% Non-variable ~17% Periodic, non-sinusoidal ~12% Aperiodic, burster ~11% Search for correlations with stellar/disk parameters Comparison with models

An approach to classification Flux Asymmetry Bursters Stochasticity Purely periodic Quasi-periodic stars Stochastic stars Eclipsing binaries 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

First data release You can download YSOVAR Orion data from: http://ysovar.ipac.caltech.edu/first_data_release.html http://cosmos.physast.uga.edu/Public/

Miscellaneous slides

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

VJ3.6 60o 0.8 AU No magnetic support Neal Turner, JPL

VJ3.6 60o 0.8 AU Magnetic support near 0.1 AU

… Enter csi 2264 CoRoTSpitzer Magnitude [4.5] Time (days) CoRoTSpitzer Magnitude [4.5] 40 days

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

YSOVAR: The Young Stellar Object Variability Project