Slide 1

The Sun in its YouthAlicia Aarnio

Color palette for this template: http://design-seeds.com/index.php/home/entry/vegetable-hues2OutlineStellar evolution timelineTTS: pre-main sequence SunsdM/dtdL/dtSolar-stellar connectionCoronaeActivityMagnetic fields

This talk has three goals: one, to introduce T Tauri stars as pre-main sequence Suns. I will then describe what we know about TTS, and put their evolution into the context of a large time scale using observations of solar-mass stars of various ages. Ill focus on the evolution of the stellar mass flux and radiation. Finally, Ill discuss early T Tauri activity levels, and what we do and dont know about conditions the early Earth may have faced.3Stellar evolution in 1 slideHayashi trackHenyey trackMain sequence

Iben (1965)t [Myr]0.3 1.0 3.2 10.0 31.8 100.05.5 6.0 6.5 7.0 7.5 8.0log(t [Myr])Siess, Dufour & Forestini (2000)1.4 M0.4 M0.6 M0.2 M105 yr106 yr107 yr108 yr2e7 yr5e7 yr2e6 yr4e6 yrIsochrones are 1e5, 5e5,1e6,2e6,4e6,1e7,2e7,5e7,zams,1e8Masses are 0.2,0.4,0.6,0.8,1.0,1.2,1.44Circumstellar disksSEDsObservationsRT modelingInterferometry breaks degeneraciesInclinationRevealed inner gap

Whitney+2003bJHK, late Class I

873 Myr881 Myr1.2 GyrBooth+2009The birth line is when a star first becomes optically visible; beyond that point, enough natal material has cleared that we can see the star, and a disk around it. There is mass transfer within the star-disk system, and it looks a little something like... (next slide)

Booth et al 2009 history of solar systems debris disk [ref http://adsabs.harvard.edu/abs/2009MNRAS.399..385B ]Blackbody model results: predicts primordial Kuiper belt detectable at 24 and 70 m before the LHB. During LHB, hot dust produced as KBOs scattered inwards towards Sun, causing peak in 24 m emission. Within ~100 million years of LHB, dynamical depletion leaves KB undetectable at 24 and 70 m.

In the past decade, our understanding of protoplanetary disks has greatly increased. Inner holes have been imaged, the idea of a spherical envelope causing NIR emission in Herbigs has been dispelled. SEDs alone could not discern between a disk or a spherical envelope producing near IR excess, but mm and infrared interferometry were able to (asymmetries, inner holes) in early 2000sInterferometry has helped to break some degeneracies in SED modeling, but is inherently limited to brighter objects, for the time being.5Long-baseline IR interferometry: resolution~/b2m, 100m baseline resolution ~4mas (0.6AU at 140pc)Can presently measure visibilities (size), closure phase (shape- asymmetry?)

Tuthill, Monnier & Danchi (2001)Dust-free inner cavity

Dullemond & Monnier (2010)Inner disk measurementsIn the past decade or so, huge strides have been made toward understanding the innermost radii of TT disks. It began with interferometry of Herbigs!

LkHa 101 interpreted asymmetry as the inner dust ring of the disk, tilted out of the plane of the sky. MWC 349A shows clear disk structure.6InterferometryTransiting circumstellar disk observed with MIRCHot Jupiter atmosphere measurements

Zhao+2011

Kloppenborg+2010Stencel+2008Were getting very close to being able to directly image hot Jupiters orbiting stars; then we can model the heat distribution on the planet using direct measurements. This has been done with CHARA for a 1.3 M_J planet around nu And b, an F8V star at 13pc. Vband mag~4 !! [ref: http://adsabs.harvard.edu/abs/2011PASP..123..964Z ]

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Mass transfer in star-disk system

HadeanArcheanPreterozoicPhanerozoic

Hartigan+1995- Cranmer & Saar 2011Haisch & Lada2 2001Meyer+2008- Wood+2005On the plot, I show more steady-state sorts of values, then the animations that pop up afterward talk about some episodic things- FU Ori events with pulses of high accretion, and then a movie of HH 30, which is losing mass from the jet at 10^-7-10^-8 Msun/yr. On the early end of the plot, the winds and outflows are likely accretion driven, so the energy brought into the system via accretion doesnt change fundamental stellar parameters, it goes right back out in other forms.The bottom line is really that the mass going in is bigger than the mass going out, and these large-scale exchanges occur over too short a timescale for us to think the Sun started out much higher mass.

Filled areas: geological epochs. Hadean, Archean, Preterozoic, Phanerozoic. Arrows pointing up from X axis are dates of oldest mineral/rock found on Earth- Zircon from Australia, and the Acasta Gneiss.LHB marked off with white vertical lines; pink vertical line is when the Sun hit the ZAMS (5e7 yr); orange vertical line is the moon forming event.Diamonds are Hartigan, Edwards & Ghandour (1995)- accretion rates measured from veiling, outflow rates from the high velocity component of the [O I] line. Dupree+2005 use O VII for TW Hydra and get Mdot=2.3e-11 Msun/yr, then also use C III and get Mdot=1.3e-12 msun/yr. Using Halpha for TW Hydra, you get 10^-10 msun/yr! Much scatter yet, likely due to our not really knowing exactly where, spatially, the emission is originatingFEPs 24 micron excess data Carpenter+2008 [ref http://adsabs.harvard.edu/abs/2008ApJS..179..423C ]JHKL excess data from Haisch, Lada, and Lada (2001) HH 30 animated gif found here: http://hubblesite.org/newscenter/archive/releases/2000/32/image/c/ paper on binarity: http://adsabs.harvard.edu/abs/2008A%26A...478L..31G paper on mass loss rate from jet: http://iopscience.iop.org/0004-637X/721/2/929/fulltext/ Mdot~10^-7 to 10^-8 solar masses per yearFU Ori accretion figure from Zhu+2010Mass loss measurements via astrosphere emission: t^-2.33 power law of Wood+2005 [ref http://adsabs.harvard.edu/abs/2005ApJ...628L.143W ]

8Evolution of radiation fieldHadeanArcheanPreterozoicPhanerozoic Ingleby+2011 Getman+2005 Wright+2011- Siess+2000 Ribas+2005 Mamajek & Hillenbrand, 2008

**All quantities plotted here are shown relative to current solar values.**L_fuv/L_bol for K types from Ingleby et al. 2011.Lx/Lbol for COUP stars from Getman et al. 2005. Ages from Hillenbrand (1997).Mean Lx/Lbol for cluster stars from Wright et al. (2011; http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=J/ApJ/743/48 ) compilation. Error bars represent min/max Lx/Lbol values; only 1.0 M_sun stars shown here for every cluster.Total stellar FUV flux with respect to solar FUV flux in same wavelength range (1-1180A) from Ribas et al. 2005.Mamajek and Hillenbrand (2008) evolution of log(Rx) as a function of time (function given in Appendix; tau as a fn of Rx).Siess et al. (2000) evolution of Lbol for a 1 M_sun star.9Solar-stellar connection: X-ray propertiesX-raysX-ray emission properties like the Sun

Adapted from Schmitt (1997)Figures from Peres+2004

From Marino+2002b

Solar minSolar max X9 flare

QCARAR coresFlaresFlares: Reale+2001All else: Orlando+2001

Stellar and solar dataAll the items Ive discussed before have been assessed somewhat independently of the solar case: we can derive collapse timescales for gas, we detect bulk motion of material in spectra, and we see periodicities in light curves. How do these then connect to the solar case, and how can what we know about the Sun help us interpret stellar observations?Hardness ratio = HR= (H-S)/(H+S) where H is the xray flux in the 0.55-1.95keV band and S is 0.13-0.4keV.Generally, the hotter the plasma, the more positive the HR.10Magnetic activityFlares much like the Sun, but more frequent, energetic

Classifying TTS flares like solar, COUP flares = X300-X40,000!Solar-stellar connection: flares, fields

Getman+2005

----- 1-8----- 0.5-4

E. Flaccomio for COUP collaborationAarnio, Stassun & Matt (in prep)Its important to understand the magnetic fields of TTS because they transfer huge amounts of energy and provide a conduit for the bulk motion of plasma in the system11Ramifications for planet formationActivity can impact planet formationChondrule formation via shock heating of CME hitting disk- Miura & Nakamoto (2007)Composition of diskStrong early winds, frequent CMEsAtmospheric strippingoxidation, chemistry changesUnderstanding young exoplanet magnetospheresTidal forces on hot Jupiters- Trammell, Arras & Li (2011) Star-planet magnetospheric interaction causing chromospheric variability- Shkolnik et al. (2008)Shock-heating formation of chondrules: Miura & Nakamoto, 2007 (Icarus)Hot jupitershttp://iopscience.iop.org/0004-637X/738/2/166/fulltext/Terrestrial planetshttp://online.liebertpub.com/doi/abs/10.1089/ast.2006.0127Tidal forces on hot jupiter magnetosphereshttp://adsabs.harvard.edu/abs/2011ApJ...728..152TEvghenya Schkolnik- Ca II line variability as indicators of planet-star magnetic interactionhttp://adsabs.harvard.edu/abs/2008ApJ...676..628S12

Aarnio et al. (2012)Magnetic loops ~10R*Cool plasma: prominences, ``clouds (A. Collier Cameron, AB Dor)Confining hot plasma: post-reconnection loops (UCL model, Reale+1997; applied to COUP Favata+2005)Large-scale magnetic structure

Collier Cameron & Robinson (1989a)Unlike the solar case, the extended coronal structure we see on stars are of greater scales than ever seen on the Sun- beyond the closed corona, beyond corotation. Sometimes they occur on stars with close-in dust disk truncation radii, most of the time they arent (inner edge of disk could inhibit formation of large structures, truncate corona by stripping).Using solar magnetic field models, we validate large loops a posteriori13Stellar CMEsPost-flare loops: 1019-1022 gOur stellar CME mass loss rates: ~10-9 10-11 M/yrAarnio, Stassun & Matt (in prep)

We use the activity rate because that is better constrained than the wind estimates problem with TTS winds is that detectable outflows often driven by accretion, which has largely turned off by the time planets are formed and evolving.

Prominences observed:AB Dor (50 Myr): 2-6x1017g (Collier Cameron & Robinson, 1990)Speedy Mic (30 Myr): 2x1017g (Dunstone+2006)

14SummarySun-as-a-star and stars-as-suns valuable for better understanding bothStellar evolution generally understood, but many issues remainRotation/activity relationshipBInitial conditions in protosolar systemChemistryDisk structureAngular momentum evolutionCollaboratorsUM: John Monnier, Nuria Calvet, Chuck CowleyVU: Keivan StassunCEA Saclay: Sean MattBU: Jeff Hughes, Sarah McGregorCal Tech: Scott GregorySt Andrews: Moira Jardine, Joe LlamaWork Ive mentioned in this presentation was done in collaboration with...16Hidden slides!In case questions arise, or I have extra time.

Image here is from Cranmer paper describing how accretion could indeed power stellar winds (as suggested by Matt & Pudritz)17Magnetic field measurements~kG surface fieldsComplex topologyHussain et al. (2007)Contemporaneous DZI, X-ray Spectroscopy to reveal field structure at surface, in coronaO VII triplet used as density diagnosticSurface field maps extrapolated outward; met by X-ray derived density/temperature constraintsX-ray corona likely only extends to 0.4 RCorrelation found between active region indicators at surface (spots) and in corona (X-ray bright plasma)

Field strength, GSpot coverageObservations

Prominence(EUV absorption)Mapping the corona of AB Dor

Here, I want to show an example of how stellar magnetic fields are measured.. I should probably get one of the field maps from Scott Gregory or J-F Donati.. This might be a little too much detail, but I really like the coronal X-ray emission plot.

The amount by which the narrow line is doppler shifted depends on projected distance from rotation axisFeature appears in every photospheric absorption line in the stars spectrumhttp://star-www.st-and.ac.uk/~acc4/coolpages/imaging.htmlObserving polarization, Zeeman splitting, Doppler shifts of lines over a rotation periodField strength (Zeeman)Field orientation (polarization)Location of features on surface (Doppler line shift)Reveals surface field structure18Solar-stellar connection: flares, fieldsMagnetic activityFlares just like the Sun, but much more energetic, frequent

Aarnio+2011This figure is from my solar physics paper, it shows in the hatched region what the ttauri flare fluxes look like compared to the solar flare fluxes.19Skumanich (1972) used data from multiple open clusters Pleiades (70 Myr)Ursa Major (120 Myr)Hyades (600 Myr)and the Sun (4.5 Gyr)As a function of age, Li abundance, surface rotation rate, and Ca+ emission decay as t-Li appears to begin to decay exponentially around the age of the Hyades

Evolution of activity20values represent means for each cluster (median?) and error bars show spread in data

The activity-rotation relationship could be a conference in and of itself.. Suffice it to say, for now, that in general, as stars age, all of these parameters decline with behavior describable with various power laws. Activity, and the hard X-ray emission produced as a result, decreases with time.

Pizzolato+2003

Gudel, Guinan & Skinner (1997)More activity evolution figures..21Herbig Ae/Be starsInner rim models fit both TTS, HAeBe SEDs, interferometryStability of puffed-up inner rim potentially explicable by:Hot, optically thin gas interior to rimHigher refractory index of grains than previously thought

Dullemond, Dominik & Natta (2001)How SED models improved once we realized there was a puffed up inner disk rim and a gap close to the star. Addition of rim reconciles the SED with the interferometry over all wavelengths. If it werent for herbigs, we wouldnt have suspected much was special about the inner edge of the disk!These are adapted Chiang & Goldreich SED models; assumes a 2-temperature disk, different regions of disk have analytical approximations for radiative transfer within that region.22

NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA), the Hubble Space Telescope Orion Treasury Project Team and L. Ricci (ESO)Proplyds in orion, like the snapshots on my title slide.23