The excess The excess emission in emission in

Classical T Tauri Classical T Tauri StarsStarsJorge Filipe S. GameiroJorge Filipe S. Gameiro

DMA, Faculdade de Ciências Universidade DMA, Faculdade de Ciências Universidade do Portodo Porto

Centro de Astrofísica da Universidade do Centro de Astrofísica da Universidade do Porto (CAUP)Porto (CAUP)

Collaborators:Daniel Folha, Vitor Costa (CAUP)Nuria Calvet (CfA), Rui Azevedo (CAUP/CfA)Peter Petrov (Crimean Astrophysical Observatory)

OutlineOutline

Star disc interactionStar disc interaction Magnetospheric accretion models to fit the Magnetospheric accretion models to fit the

excess emission (veiling) dependence on excess emission (veiling) dependence on wavelengthwavelength

Accretion rate determinationAccretion rate determination The inner disc structure The inner disc structure

Combine NIR and optical observationsCombine NIR and optical observations What is the connection between optical and NIR What is the connection between optical and NIR

excesses?excesses? Short time scale variability – Short time scale variability –

Inhomogeneous accretion Inhomogeneous accretion

I – Star-disc interactionI – Star-disc interaction

RU Lupi – CTTSRU Lupi – CTTS HR7368 – template (K7V)HR7368 – template (K7V) RX1524.0-3209 – WTTS (K7V)RX1524.0-3209 – WTTS (K7V)

Aexcphot FFF 4.0* 10)(

Veiling Measurement procedureFe II (

temptemp

temp

F

Fr

F

FFr

1

DI Cep (G8IV-V)Template (G8V)

-1s km 1.5 20.2 )sin( Iv

Residual spectrum

Veiling dependence on wavelength – DI CepVeiling dependence on wavelength – DI Cep

OHP (ELODIE) / 1997

WHT (UES) / 1999

NOT (SOFIN) / 2001

Steep rise clearly seen around 4500 Steep rise clearly seen around 4500 ǺǺ Veiling tends to increase towards short wavelengthVeiling tends to increase towards short wavelength Veiling increase towards near infra-red ?Veiling increase towards near infra-red ? Hump feature centred at 5300 Hump feature centred at 5300 ǺǺ and about 500 and about 500 ǺǺ

wide (also reported by Stempels & Piskunov 2003)wide (also reported by Stempels & Piskunov 2003)

Magnetospheric accretion shock modelsMagnetospheric accretion shock models

Camenzind 1990, Konigl Camenzind 1990, Konigl 1991, Shu et al. 19941991, Shu et al. 1994

Magnetospheric accretion models have been successful in explaining the excess emission (continuum and lines) Calvet & Gullbring Calvet & Gullbring 1998, Gullbring et al. 20001998, Gullbring et al. 2000 (BP Tau)(BP Tau)

Parameters of model – Parameters of model – Excess spectrum depends Excess spectrum depends

mostly on energy flux of the mostly on energy flux of the accretion flow accretion flow FF and the and the projected surface coverage of projected surface coverage of the accretion column the accretion column ff

13

18-1-2-10

01.02

5.0

10

)cos( s cm erg 10 9.8

f

R

R

M

M

yrM

M

sunsunsun

F

fM ,,T ,R , eff** F

(Calvet & Gullbring 1998, Ardilla & Basri 2000)

Accretion column

Hot spot

Disc Dust and gas

Disc gas

(Camenzind 1990)

NIR

FIR

optical

Veiling dependence on wavelength – DI CepVeiling dependence on wavelength – DI Cep

0.168 11.0, )log(

0.067 11.5, )log(

0.024 12.0, )log(

f

f

f

F

F

F1999 July 28

01.025.0

s cm erg108.910 )cos(

31

1-2-1018- f

R

R

M

MyrM

sunsunsunM

F

In agreement with results found from UV data (Gómez de Castro & Fernandes 1996)

%4.2

0.12)log(

M 104.2 -109.1 )cos( 1sun

7-8-

f

yrM

F

Results

II-The inner disc II-The inner disc structurestructure

NIR continuum excess is higher than predicted by simple models (Folha & Emerson 1999, Johns-Krull et al. 2001)

NIR emission arises from an inner disc rim at the dust sublimation radius (Natta et al. 2001, Muzerolle et al. 2003)

Accretion column

Hot spot

Disc Dust and gas

Disc gas

(Camenzind 1990)

NIR

FIR

Simultaneous observations Simultaneous observations in the NIR and optical in the NIR and optical

bandsbands South hemisphere (ESO)South hemisphere (ESO)

NIR – NTT (SOFI) [cover the 0.9-2.5NIR – NTT (SOFI) [cover the 0.9-2.5m m wavelength range]wavelength range]

Optical – 1.52m [Boller & Chiven Optical – 1.52m [Boller & Chiven spectrograph (low resolution)]spectrograph (low resolution)]

27 CTTS, 9 WTTS27 CTTS, 9 WTTS North hemisphere (La Palma)North hemisphere (La Palma)

NIR – TNG NIR – TNG Optical WHT (ISIS) [spectral coverage Optical WHT (ISIS) [spectral coverage

3600-9000 A]3600-9000 A] 16 CTTS, 8 WTTS16 CTTS, 8 WTTS

CTTS span a large range of excess emissionCTTS span a large range of excess emission WTTS used to derive the excess emission WTTS used to derive the excess emission

spectra. They spectral type cover those of spectra. They spectral type cover those of CTTS in the sampleCTTS in the sample

The spectra are calibrated in absolute fluxThe spectra are calibrated in absolute flux The observations allow us to determine the The observations allow us to determine the

spectrum of excess continuum from the spectrum of excess continuum from the blue , where emission from the shock blue , where emission from the shock dominates, to the K band, where emission dominates, to the K band, where emission from accretion disc starts dominatingfrom accretion disc starts dominating

Disentangle the various source of excess emission

T=2400K

6200

0.4A*

*

V10

2002) Piskunov & (Stempels 3.0AF

F1. = Dereddened flux

2. Measure veiling at 6200 A (r=4.0)

3. Scale template spectrum

4. Get absolute excess emission1

10 4.0

r

FF

Aphot

photF

AF 4.0* 10grisms

Absolute excess emissionAbsolute excess emission

• With these observation we relate excess continua from the blue to the NIR. Adjust various component to the obtained spectra, namely those resulting from accretion shock and accretion disc models• Two independent way to determine mass acretion rate (accretion shock component from optical observations, Pa and Br line fluxes [Muzerolle et al. 1998])

photAexc FFF 10*

Veiling excessVeiling excess

6200

• Veiling determined from the absolute fluxes of star and template• Veiling increase towards NIR wavelength.• Bump at 5300 A due to molecular absorption band (TiO)

Veiling = 4 at 6200 Ǻ

III – Accretion rate III – Accretion rate variability in short time variability in short time

scalesscales BP Tau ObservationsBP Tau Observations

Double arm spectrograph ISIS on the WHT Narrow slit (≈1”) Δv≈6 km/s (blue arm) + Δv≈20

km/s (red arm) One hour long time series: Δt≈5 min. (blue arm) +

Δt≈1 min. (red arm)

BP TauBP Tau

Classical T Tauri star, K7Classical T Tauri star, K7 Teff=4055 Teff=4055 ±112 K±112 K Log Log g =g = 3.67 3.67 ±0.50±0.50 vv sin sini = i = 10.210.2 ± 1.8 km/s± 1.8 km/s ii = 28º = 28º ±2º ±2º Dutrey, Guilloteau & Simon Dutrey, Guilloteau & Simon

(2003)(2003)

Photometric period = 6.1 – 8.3 daysPhotometric period = 6.1 – 8.3 days Irregular short time scale variabilityIrregular short time scale variability

Johns-Krull, Valenti & Koresko (1999)

Lines variabilityLines variabilityH e I (6678)

• H displays a decrease in intensity and significant narrowing at the base• He I reveals the presence of an inverse P Cygni profile on the first 12 minutes that disappears• The veiling decreases

Variability can be due to:Variability can be due to: Obscuration by circunstellar material – Obscuration by circunstellar material – But veiling variations !But veiling variations ! Flare like event – Flare like event – possible but the likelihood of catching a flare possible but the likelihood of catching a flare

in one hour is very small, Gullbring et al. 1996 found no in one hour is very small, Gullbring et al. 1996 found no pronounced flare activity on BP Taupronounced flare activity on BP Tau

Rotational modulation – P=6.1-8.3 daysRotational modulation – P=6.1-8.3 days Accretion rate variation – Inverse P Cygni He IAccretion rate variation – Inverse P Cygni He I

1 hour

Model fits BP Tau data set:

M*=0.5 M, R*=2 R, Teff= 4000 K (no Av assumed)

1-component models (1C)

single log F2-component models (2C)

pair of log F

phot,0λ

shockλ

λ F)-(1

F1r

f

fphot,0λ21

shock,2λ2

shock,1λ1

λ F)1(

FF1r

ff

ff

log F =10.5 log F =11.0 log F =11.5

log F =10.5

log F =11.0

log F =10.5

log F =11.5

log F =11.0

log F =11.5

1C

2C

observations model results

1C

2C

Inhomogeneous Inhomogeneous accretionaccretion

The accretion rate starts off at The accretion rate starts off at relatively high value relatively high value

Decrease in 1 hour to Decrease in 1 hour to

17107.1 yrM sun

18100.5 yrM sun