Transcript Interferometric Doppler Imaging of Chemically Peculiar stars

Interferometry in the visible
Young Stellar Objects
M. Benisty, S. Kraus, K. Perraut (leader), G. Schaefer, M. Simon
Science cases for visible interferometry – Nice, January, 15th
1
Scientific rationale
Nuage moléculaire
Molecular
clouds
(Taurus)
Effondrement
Collapse
1 pc ― 20’
10 pc ― 4°
Accretion disk and bipolar ejection Debris disk and protoplanets
106 yrs
0.1 pc ― 2’
Planetary system
old
[Bouvier & Malbet 2001]
105 /
Fragmentation
Fragmentation
1000 AU ― 7’’
300 AU ― 2’’
30 AU ― 0.2’’
Outline

Fundamental parameters of YSO

Complex environment

Summary of High-Level Requirements
3
Outline

Fundamental parameters of YSO

Complex environment

Summary of High-Level Requirements
4
Fundamental parameters of YSO
For low-mass (M < 1 Mʘ)
young (< 10 Myr) PMS stars
the mass and age estimates
vary according to the
evolutionary tracks used.
 The mass spectrum of low mass stars (the majority!) is
imprecisely known.
 The chronology of planet formation is also imprecisely
known.
5
Situation and opportunities
M < 1 Mʘ : Dynamical measurements of masses will
“calibrate” the theoretical calculations of evolution.
Masses < 0.5 Mʘ are particularly required.
 Studies of Taurus and Ophiuchus star forming
regions (1 to few Myr; 120-160 pc)

M > 1 Mʘ : Theoretical calculations are consistent.
Hence diameter measurements of a star determine its
age!
 Studies of stars in the older (10 Myr +), but closer
(few pc +) “Nearby Young Moving Groups”

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Interferometric measurement
Angular Resolution (mas) at
Baseline (m)
 = 0.6 µm  = 1.0 µm
 = 1.5 µm
100
0.62
1.03
1.5
200
0.31
0.51
0.77
300
0.21
0.34
0.5
1 AU orbit at 140 pc (eg Tau and Oph) subtends 7 mas.
 at 10 pc: 1.0 mas (Sun); 0.5 mas (M0V)
 Angular diameters in Tau or Oph unresolvable
 Interferometric measurement of dynamical masses in these
regions possible for visual binaries and some SB
 Diameters of F and G stars in Nearby Young Moving Groups
resolvable if close enough
7
Census of dynamical masses
MIRC observations of s Ori Aa-Ab
[Schaefer et al., in prep]
N=8
N=4
N=8
Resolved
Spectroscopic
Binaries
Eclipsing
Binaries
Masses with precisions measured to better
than 10%
MAa = 16.8 ± 0.4 M⊙
MAb = 12.8 ± 0.3 M⊙
d = 385 ± 3 pc
 Few precise masses below 0.5 Mʘ
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Resolving PMS Spectro binaries
Taurus-Auriga
Ophiuchus
Sco-Cen
Chamaeleon
Orion
NGC 2264
a sin i (mas)
Resolved SB2
Spectral Types: F-M
PMS binaries resolved
with a baseline of 300 m
Eclipsing
SB2
R-band
K-band
39
21
V (mag)
 Going down to R-band doubles the sample
3D structure of Taurus SFR
Stars with measured proper motions
[Ducourant et al. 2005]
CO clouds
[Dame et al. 2011]
Stars with measured distances
[Torres et al. 2009;
Simon et al. 2013]
The clumps where stars
formed range from 131 to
161 pc.
 Need distances to
L1495N, L1551 (hosting
GG Tau)
Nearby Young Moving Groups
NYMGs are stars known to exist in the vicinity of the Sun as
members of “moving groups” each consisting of stars moving
in the same approximate direction with the solar
neighborhood.
They are young:
8-12 Myr ( Pic moving group)
~ 40 Myr (AB Dor moving group)
They are nearby:
from a few to 100 pc.
Most members of the NYMGs are Known members of  Pic NYMG
[Schlieder et al. 2012]. Spectral
in Southern hemisphere but some type is coded by color.
members of  Pic and AB Dor are in
the North.
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Measure diameter of stars in NYMGs
 Pic MG
HIP 21547 (0.518 ± 0.009 mas)
HIP 25486 (in progress)
HIP 560 (0.492 ± 0.013 mas)
[Simon & Schaefer 2011]
AB Dor MG
[Schlieder 2012, PhD Thesis]
NOTE: angular diameter (mas) scaled
to a common distance of 10 pc
Measure diameter of NYMG members
V mag
Star number
Spectral Type
3-4
1
A
4-5
1
A
5-6
3
2A, 1F
6-7
5
5F
7-8
6
4F, 1G, 1K
8-9
3
9-10
4
10-11
13
11-12
11
12-13
6
13-14
2
14-15
1
Mostly G and K
Mostly M
Known members of  Pic NYMG in 2008
[Torres et al. 2008].
All the F stars can be
resolved at 1 μm with
baselines ≥ 100 m
F stars are in the “sweet spot”
for angular diameter and
hence age measurement: they
are bright, near to us, their
evolutionary tracks are
reliable, and they are still
above ZAMS.
Outline

Fundamental parameters of YSO

Complex environment

Summary of High-Level Requirements
14
Structure of a protoplanetary disk
[Dullemond & Monnier 2010]
15
The complex innermost regions

Near-infrared (spectro-)interferometry directly probes the
emission within the innermost astronomical unit (AU), where key
quantities for the star-disk-protoplanet(s) interactions are set.
The regions probed by this technique are much more complex
than expected.

3D MHD simulations of accretion (driven by magneto-rotational
instability) on to a rotating magnetized star with a tilted dipole
magnetic field produce complex maps.

All these complicated inner
disk structures are strongly
time variable on a timescale
of weeks to years …
[Romanova et al. 2012]
Accretion-ejection phenomena

Accretion via the accretion columns (T Tau) or the inner disk





Connections star/inner disk, inner disk/dust disk ?
Morphology of the inner rim of the dust disk ?
Processus of dissipation and evolution of the disk ?
Law of temperature, velocity, density in the disk ?
Ejection via a wind (star, disk, …) and jets
 Launching point and morphology of jets ?
 Mechanisms that favor jet collimation ?
 Mass-loss rate wrt mass-accretion rate ?

Formation of the Hydrogen emission lines
 Connection between accretion and ejection
 Line forming regions ?
 Mechanisms that could explain the temporal variability ?
17
Visible spectral lines
DG Tau vs. FU Ori spectra
Forbidden lines (e.g. [OI], [NII], [FeII], [SII])
Ha (and also Ca II triplet at 850/854/866 nm)
Trace low-density gas,1 sometimes
withpc
R* = 0.07associated
mas @ 140
andlikely
outflow. However, this emission is typically
Accretion tracer [Hartmann et al.jets
1994],
 Requires very high
distributed
over
tracing structures on the stellar surface
and in
themany arcseconds [Podio et al. 2011;
Bacciotti
magnetospheric accretion columns
(3-5 R*et
) al. 2002] angular resolution
 possibly overresolved with interferometry
Visible spectral lines
Lines
 (nm)
EW (Å)
Ha
656.2
20 - 150
Ca II triplet
849.8
854.2
866.2
0.5 - 50
He I lines
667.8
706.5
0.5 – 2
O I lines
777.2
844.6
-1.6 - 8
[0I] line
630
< 15
[SII] line
673.1
<5
[FeII] line
715.5
<2
 Requires very high
spectral resolution
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The He I1.083 line
[Edwards et al. 2003]
• A unique diagnostic of kinematic
motion in the regions close to the
star.
• High opacity: a very sensitive
probe to the geometry of the
mechanisms at play.
• He I line is composite:
• Blue-shifted absorption (wind)
• Red absorption (accretion)
[Kurosawa et al. 2011]
 Very compact wind (few R*) that
requires very high angular resolution
20
Accretion in close binaries
• Stars orbit in a gap opened by tidal interactions inside a
circumbinary disk.
• Young short period binaries (P < a few 10 days, sep ~ a few
0.1 AU) cannot support large circumstellar disks.
 Circumbinary disk
• Evidence of enhanced emission line activity close to
periastron passages (DQ Tau [Basri et al.1997], UZ Tau E [Martyn
et al. 2005])
non-axisymmetric accretion
[de Val-Borro et al. 2011]
21
Simulated accretion streamers
V4046 Sgr
[de Val-Borro et al. 2011]
0.2 mas
R mag = 9.5
Interferometry will provide a
critical test of simulations
such as these.
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Detecting low-mass companions
[Close et al. 2014]
Planets and brown dwarfs
forming in the disk should
exhibit accretion signatures
(H-a emission)
Expected contrast (companion/star)
w/o extinction
Brown Dwarf < 10-3
Jup.
< 10-4
Contrast could be dramatically
reduced due to extinction
 Requires high contrast
imaging at moderate spectral
resolution
Scattered light disk features
HD141569,
HST
Imaging in scattered light could
reveal asymmetric structures
that might be linked to planet
formation, similar as seen in the
outer disk [Mouillet et al. 2001]
HD10054
6
Combining scattered light imaging
Total integrated scattered light
in
contributions are about 100VIS/NIR
constraints
sizeflux
times
fainter thandust
stellar
distribution
and vertical dust stratification
(Mulders etal.Requires
2013) high-fidelity,
high-contrast imaging
Interest of polarimetric
mode (SPHERE) or nulling
Outline

Fundamental parameters of YSO

Complex environment

Summary of High-Level Requirements
25
Summary of High-Level Specs
Science cases
Diameter of stars in SFR
Baseline
Spectral
resolution
Imaging
A few 1000 (Ha)
1 few 10000
Yes
Unreachable
Diameter of stars in
NYMGs
> 100 m
Dynamical masses
300 m
Accretion-ejection
Hectometric
Companion
Hectometric
High-contrast
Scattered light
Hectometric
High-contrast
High-fidelity
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Limiting magnitudes
Pre-Main sequence stars in Taurus-Auriga
K
70
Object numbers
60
From Kenyon et al. 2008
50
R
40
30
20
10
0
4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5
Magnitude
In Ophiuchus, K-mags are similar but R are fainter because of greater
extinction.
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Conclusions



YSO is a strong science case for interferometry in the
visible.
Interferometric Imaging and Spectroscopy will provide
unique and complementary data for understanding star
and planet formation. The techniques will probe the
innermost regions protoplanetary disks and will enable
diameter measurements of stars still contracting to the
main sequence.
The science case is very challenging mainly because of
the brightness of targets.
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Differences among models
1.0 Mʘ
0.1 Mʘ
Increasingly ideal gas in interior
Increasingly non-ideal
Radiative transport increasingly
important in core
Radiative transport less important
Convection increasingly important
Peak of spectral energy distribution
increasingly affected by broad
molecular absorption
Therefore:
1) Equation of state
2) Radiative and molecular opacities are very important.
3) Treatment of convection
4) Model atmospheres