T Tau An Enigmatic Eponym Tracy Beck STSc

T Tau! An Enigmatic Eponym Tracy Beck (STSc. I), Gail Schaefer (CHARA), G. Duchene (Grenoble), M. Simon (SUNY Stony Brook), L. Prato (Lowell Obs. ), Andrea Ghez (UCLA)

T Tau! The Eponymous Pre-Main Sequence Star R Cr. A RU Lup RW Aur UX Tau T Tau R Mon The Original 11 (Joy, 1945) – Stars with absorption features typical of F-G types – Often associated with bright/dark nebular regions – Curious Emission Line spectra – Highly Variable in Brightness (up to 3+ mag) RY Tau S Cr. A XZ Tau UY Aur UZ Tau

T Tau! An Enigmatic Eponym • T Tau was chosen to represent the new class of variables because it was: – Among one of the brightest members of the new class – The best studied of the sample – Showed a good range of the absorption/emission features used to characterize the set of stars

T Tau Prior to 1945… • In the Beginning, there was J. R. Hind… – In October 1852, Hind reported on the discovery of a nebulosity ~35” from an apparently variable ~10 th mag star – (T Tauri, of the variable star catalogs) – After many observations of this nebula in the 1850’s, several articles in the 1860’s noted that it was no longer visible Hind’s Variable Nebula (NGC 1555) – Burnham (1890) discovered a second nebula nearby to T Tauri, extending ~4” to the South (Burnham’s Nebula, known today as HH 255)

T Tau… Prior to 1945 • Early literature attempts to identify variable nebulae (difficult!) • Hind’s nebula was of particular interest (Hind, Struve, Burnham, Barnard, Temple…) • Varied by an estimated 2 -4+ magnitudes • Keeler 1900: “Hinds nebula presents an incontestable case of nebular variability”

T Tau - Hind’s Variable Nebula Hind’s Nebula (POSS 1 Blue Plate; 1950’s)

T Tau - Hind’s Variable Nebula Hind’s Nebula?

T Tau - Historical Variability? • What causes a 45” extent nebula to disappear? • Why is Hind’s nebula not so variable today? • Could there be a link between T Tauri’s variability and Hind’s nebula?

T Tau - Historical Variability • Figure 5 from Lozinskii (Peremennie Zvezdi, 7, 76, 1949) (? ? ? )

T Tau - Historical Variability Blue Emulsion Plates from the Harvard College Observatory Plate Archives 1898 to 1953 (Beck & Simon 2001)

T Tau - Historical Variability • T Tau varied in optical brightness by more than 3 -4 magnitudes until the mid ~1920’s. Then this level of variability just STOPPED. • The optical continuum flux from T Tau is still variable (e. g. , Herbst et al. 1994) but not on the same scale, only by only ~+/-0. 4 mag.

T Tau - Historical Variability • Lorre (1975) digitized Lick Blue Emulsion Plates from 1899 -1963 from the 36” and 120” telescopes (digital PSF subtraction) • NGC 1555 Brightened and stabilized considerably in early 1930’s Conclusion: Early variability of T Tau and surrounding (scattered light) nebulosities occurred because of changes in obscuring material close to the star * 6 Dec. 1899 27 Dec. 1899 30 Oct. 1914 16 Nov. 1914 10 Feb. 1951 4 Feb. 1953

T Tau - A Whole Range of “Firsts” • First Confirmed Variable Nebula • Prototypical Pre-Main Sequence Star • Burnham’s Nebula - the 4” extent nebula to the South of T Tau - was used to help define a new class of Astronomical Sources known as “Herbig -Haro Objects” (Herbig 1950) • Beckwith et al. (1978) first detected near IR rovibrational H 2 emission in YSOs in T Tau • Brown et al. (1981) first detected UV electronic transitions of H 2 in YSOs in T Tau • The Prototypical “IR Luminous Companion” System…

T Tau - It’s IR Companion Dyck, Simon & Zuckerman (1982) report the detection of an infrared luminous companion to T Tau; ~0. ” 6 (100 AU) South of the optical star “T Tau North” = Optical Star “T Tau South” = IR Companion

T Tau North and South Stapelfeldt et al. (1998) analyzed HST optical WFPC 2 images of T Tau, but didn’t detect the IR Companion to V~19. 6 Mag! Yet… T Tau S is brighter than T Tau N in the IR at wavelengths greater than ~3 m

T Tau - IR Flux Variability • T Tau N Doesn’t vary in IR flux (to ~0. 1 mag) • IR Variability of T Tau S - Originally detected by Ghez et al. (1991) • Shown here = 20 years of K & L-band IR variability (Beck et al. 2004)

T Tau - IR Variability • IR Variability in K and L-band for T Tau S shows a “redder-whenfaint” character typical of changes in obscuration that follow an ISM extinction law

T Tau - Sigh…. An Enigmatic… Triple? • Using IR Speckle techiniques at the W. M. Keck Observatory, Koresko et al. (2000) reported that T Tau is in fact a YSO TRIPLE, T Tau S has a ~0. ” 05 (7 AU) separation companion!

T Tau! An Enigmatic YSO Triple • Yep. There it is. “T Tau Sb” is confirmed by Duchene et al. (2002) “T Tau South A” “T Tau South B”

T Tau - Reconciling IR and Radio Data? • The Measured IR and Radio positions of T Tau S (unresolved) from 1980 onwards have never agreed entirely • Loinard et al. (2003), Johnson et al. (2003) - the detected Radio flux comes exclusively from T Tau Sb & This provides a way to trace the orbit of T Tau Sb back through the radio data!

T Tau! A Privileged View of a Stellar Ejection? • Stellar Ejection Event? • Radio data had no reference position for T Tau Sa, assumed it’s location was static! Figure 3 from Loinard et al. (2003)

T Tau - IR vs. Radio Positions? • Dashed line = average IR position of T Tau S • Points = Measured Radio Positions • (IR = Sa, Radio = Sb)

T Tau Sb - (I’d like to Get Rid of Sb…) but there’s NO Ejection! • Radio data referenced to the moving IR position of T Tau S shows NO evidence for an ejection event! • Perhaps more importantly, IR and radio positions for T Tau Sb don’t coincide for data from 2001 (differ by ~40 mas)

T Tau - The Nature of the YSO Triple Stars T Tau N, the Optical star, is an actively accreting YSO with IR disk excess, low Av, and a stellar type of ~K 0. AO-fed IR spectroscopy shows that T Tau Sb is a young spectral type ~M 0 star with IR excess emission, seen through about ~8 mag of Av (Duchene et al. 2002)

T Tau Sa - What the…? • Orbital analysis of the T Tau system… • BOTH stars referenced to the position of T Tau N • Schaefer et al. (2006)

T Tau Sa - What the…? • Schaefer et al. (2006) • Analyzed 10, 000 possible orbital solutions for the Sa-Sb system and derive a distribution of possible masses • Mean Mass = 4. 13 +1. 58/-0. 97

T Tau Sa • T Tau Sa - A ~3 Solar mass star • Though it is optically invisible, T Tau Sa is the most massive star in the T Tau system! • It is ~50% more massive than T Tau N (one of the brightest & most massive YSOs in Taurus!) • How can this be?

T Tau - A look at Circumstellar Material in the System Akeson, Jensen & Koerner (1998) found 3 mm continuum emission - typical of cold dust in YSO disks - toward T Tau N, only! (limiting detection for T Tau S ~9 m. Jy) Work by Akeson et al. (2002; 2005), Eisloffel et al. (1988); Herbst et al. (1986) all suggest that T Tau N is viewed pole-on, & with a disk that is viewed nearly face-on

Amorphous silicates, young, embedded YSOs Circumstellar Disks in the Infrared… • To better understand T Tau, a reminder of the “evolution” of disk diagnostics in the IR • Evans et al. (2003) Spitzer Legacy - “From Molecular Cores to Planet Forming Disks” • (Kessler et al. 2005; Furlan et al. 2006) Crystalline silicates, evolved disks, grain growth

T Tau - Mid Infrared Silicates from YSO Disks • 10 m spectra • silicates in emission in T Tau N, but Absorption in T Tau S

T Tau! Emission/Absorption from Silicates • Continuum removed • T Tau N shows emission only, with structure caused by silicate processing and crystalline components (enstatite 10. 2, forsterite 11. 3 m) • T Tau S mostly amorphous silicate absorption

T Tau! 10 m Spectroscopy • Skemer et al. (2008) showed that the 10 m silicate absorption may arise from T Tau Sa, only!

A Quick Summary… • T Tau N - A K 0 spectral type YSO with low Av, a circumstellar disk viewed virtually faceon, and silicates in emission • T Tau Sb - A ~M 0 star seen through an Av of ~8 mag with no firm evidence for silicates • T Tau Sa - a ~3 Msolar YSO, obscured by ? ? (presumably 8 or more) mag of Av, with strong silicates in absorption

T Tau - Disk Inclination Effects? • Chiang & Goldreich (1997; 1999) passive disk models with inclination effects: – Superheated surface layers of inner YSO disks can give rise to silicates in emission, if viewed face-on. – YSOs with disks viewed edge-on will have dust features in absorption – Inclination effects can, however, account for only a factor of ~2 difference in mm wavelength dust emission (remember, T Tau N’s 3 mm dust was ~6 x brighter than the null detection from T Tau S).

T Tau - Disk Inclination Effects?

T Tau! Perpendicular Disks? • Arguably the best studied example of noncoplanar disk material in a YSO multiple system • Not just silicates, but also: – IR spectra and SEDs (Duchene et al. 2005) – 3 m Water Ice absorption (Beck et al. 2004) – H 2 emission morphologies (Brown et al. in prep) – YSO Outflow morphologies - two perpendicular outflows, 3 known HH objects associated with T Tau (Solf & Bohm et al. 1999; … outflows Robberto et al. 1995)

T Tau! System Geometry T Tau N, disk viewed face-on T Tau S, obscured by a circumbinary distribution of material Sa/Sb each have their own (truncated) disks (Historical variability caused by orbital motion of T Tau S w/r/t N? )

T Tau! Perhaps Best Studied, but NOT Unique! • The IR Luminous Companion Phenomenon: – Zinnecker & Wilking (1992) first postulated that 10 -15% of all YSOs have “IR Luminous Companions” – Optically undetected or faint, highly variable in flux, likely more massive than their optical primaries (Koresko et al. 1997) T Tau (prototype) Haro 6 -10 UY Aur XZ Tau V 773 Tau Z CMa WSB 4 Do. Ar 24 E Glass I VW Cha ��SZ 77 VV Cr. A

The IR Luminous Companion Phenomenon • Dynamical Evolution in YSO High Order Multiples – In an attempt to model the observed characteristics of T Tau Sa & Sb, Reipurth (2000) proposed that the IR Luminous Companions are a result of dynamical evolution in high order multiples – Vast differences in Obscuration arise from geometries where system components are presently viewed through remnant material (e. g. circum-system disks) – Alternative interpretation to purely “Perpendicular Disks”, but both invoke dynamical evolution

Mis-aligned Disks in YSO Multiples? • Jensen et al. (2004) - Polarimetry measurements of disk alignment in YSO binaries and higher order multiples – 8 YSO binaries have significant deviations from coplanarity (though orientations differ by <30 o) – 5 o 5 YSO triples or higher order multiples show disk alignment that deviates at a higher level from coplanarity - disks are misaligned to >120 deg between some components (Formation Mechanism vs. Dynamical Evolution? )

Evidence for Dynamical Evolution in YSO Multiples HK Tau - Stapelfeldt et al. 1998) PDS 144 - Perrin et al. (2006) Mis-Aligned disks in YSO multiples could be quite common

T Tau! An Enigmatic - but perhaps not Atypical - Eponym • Evolution of our knowledge of this prototypical YSO was presented dating to the very early days of modern astronomy • T Tau and its surrounding nebulosities varied in optical light prior to the early ~1930’s, but this ceased abruptly • T Tau is a YSO triple system, with two of the system components obscured to optical invisibility, viewed through extensive circumstellar material • One of the optically invisible components, T Tau Sa, is a ~3 solar mass YSO (bordering on Herbig Ae-Be star territory!) • T Tau N has low Av, with a circumstellar disk viewed nearly faceon. It shows silicates in emission, with evidence for dust processing • Dynamical Evolution could explain the observed characteristics of T Tau, and may be a common phenomenon in high order YSO multiples