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S. Sciortino – Ringberg 11.03.2005
X-rays as a probe of YSO physicsRecent XMM-Newton and Chandra
results
Salvatore SciortinoINAF – Oss. Astronomico di Palermo Giuseppe
S. Vaiana
(& lots of colleagues!)(e.g. Palermo, PennState, ESTEC,
Grenoble, MIT, Hamburg
Observatory)
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S. Sciortino – Ringberg 11.03.2005
Long (two decades) Standing Questions
Is the Young Stellar Objects (YSOs) X-ray emission always a
scaled up version of solar one ?
Can we distinguish between “pure” solar-like coronal and
star-disk interaction activity ?
What is the interplay between accretion and X-ray emission in
YSOs ?
“More Recently”: What is the effects of X-rays on small
(planetary) and large (mol. cloud) scale evolution ?
To answer we need top quality data
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S. Sciortino – Ringberg 11.03.2005
Further open issues ....
Accretion in YSOsHow is it channeled?How is it regulated?
Feedback processes?Chemistry of protoplanetary disks
How do complex molecules form?Catalyst processes and
molecules?
Isotopic ratios?
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S. Sciortino – Ringberg 11.03.2005
X-rays as a diagnostic of processes in YSOs, Why ?
Accreting (Class I, Class II) and non-accreting (Class III) YSOs
are strong X-ray sourcesClass 0 not yet firmly detected in X-rays
X-rays excellent for studying embedded YSOs
Absorption at 1 keV = at 1 µmThey provide an excellent
diagnostics of key processes in YSOs
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S. Sciortino – Ringberg 11.03.2005
A Shallow (34 ksec) XMM-Newton observation of the ρ Oph core
Next Step will (hopefully) be
DROXO, ADeep (500 ksec)Rho Oph XMM-NewtonObservation
(PI: S. Sciortino)
Ozawa, Grosso & Montmerle 2004
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S. Sciortino – Ringberg 11.03.2005
The Chandra Orion Ultradeep Project (COUP)
Central 8x8 arcmin ofCOUP
(PI: E. Feigelson)
A COUP MOVIE
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S. Sciortino – Ringberg 11.03.2005
Recent topics explored
X-ray fluorescence from YSOsFlares and sizes of magnetic
structures in YSOsX-ray Emission from Class 0 YSOs Shock-driven
X-ray emission in YSOs
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S. Sciortino – Ringberg 11.03.2005
X-ray emission from (low-mass) accreting YSOs
Very X-ray luminousAt 1 Msun, log(LX) = 30-31 (Sun:
log(LX)=26.5-27.5)
Very hotPlasma at 10's MK normally present, up to >100 MK
(Sun: >= 10 MK only during flares)
Highly time variableStochastic variability, flares, rotational
modulation
Often low metal abundance in emitting plasmaClass I/II hotter
X-ray spectra than Class III
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S. Sciortino – Ringberg 11.03.2005
Fluorescence
Emission of X-ray radiation from photo-ionized cold material
Photo-ionizing photons come from star, cold material in
circumstellar disk
Fluorescence is an obvious tracer of 'intimate relationships'
between hard X-rays and cold materialIt can give important clues to
the geometry of the circumstellar material
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S. Sciortino – Ringberg 11.03.2005
Fluorescence: what lines?
Best observable line is the Fe I Kα line at 6.4 keVHighest
yieldFe abundant
Fe I photoionized by photons with E > 7.11 keVHigh-energy
X-rays needed
Needs to be resolved from nearby Fe XXV Kα line at 6.7 keV
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S. Sciortino – Ringberg 11.03.2005
Fluorescence: observations and statistics
'Cold' Fe 6.4 keV line thus far detected in a number of casesOne
detection in YLW16A in ρ Oph during an intense X-ray flare
(Imanishi et al. 2001)7 cases of fluorescence in ONC YSOs
(Tsujimoto et al. 2005) during intense X-ray flaringOne detection
in Elias 29 in ρ Oph during quiescence and flaring (Favata et al.
2005)
Lbol
= 26 Lbol,sun
, Lacc
= 15-18 Lbol,sun
(very high)
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S. Sciortino – Ringberg 11.03.2005
Elias 29, Chandra and XMM light curves
Chandra
XMM-Newton
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S. Sciortino – Ringberg 11.03.2005
Elias 29, fluorescence
Chandra
XMM-Newton
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S. Sciortino – Ringberg 11.03.2005
Elias 29, equivalent width
Classic analysis by George and Fabian (1991) for a power law
exciting spectrum (I ~ A E
o-Г ph keV-1)
Equivalent width function of incident spectrum (known) and cold
material geometry (including viewing angle)Incident spectrum (Г ~
2.6) and EW
obs=160 ev rules
out reflection from a cold slab EW
pred < 100 ev for Г >2
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S. Sciortino – Ringberg 11.03.2005
Elias 29, equivalent width
● EW(6.4 keV) = 150 eV requires a centrally illuminated disk and
face-on viewing geometry
● IR observations (Boogert et al. 2002) indicate face-on
disk
● Chiavassa et al. (2005) observe calcite around Elias 29, =>
liquid water from X-ray heated ice on grain surface
● Ceccarelli et al. (2002) find superheated gas in disk, likely
UV/X-ray induced
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S. Sciortino – Ringberg 11.03.2005
Fluorescence in ONC YSOs
Chandra observations
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S. Sciortino – Ringberg 11.03.2005
X-ray fluorescence in ONC YSOs
EW(6.4 keV) = 110 – 250 eVUncertainties due to low
statistics
These sources must be sources with face-on disksCOUP 649 and
1040 have no NIR (JHK)excess
Fluorescence requires disksX-rays can “see” disks with no NIR
excessCan help constraining the inclination
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S. Sciortino – Ringberg 11.03.2005
Fluorescence, conclusions
Fluorescence important diagnostic of disk presence, geometry,
etc.Likely a common intrinsic occurrence in YSOsX-rays interaction
in the disk important for chemistry, etc.
Fluorescence one of the few direct tracers of such processes
Fluorescence can see disks with no evident JHK excess
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S. Sciortino – Ringberg 11.03.2005
Fluorescence, future work
Measurement of Fe 6.4 keV line at high S/N important diagnostic
of disk structureDROXO (centered near Elias 29) will provide new
high quality, time resolved spectraDetailed modeling of
fluorescence line in order to provide disk density profileTime
delay?
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S. Sciortino – Ringberg 11.03.2005
X-ray flares and size of magnetic structures
X-ray flares are classic tool to derive physical parameters of
emitting regionUse of dynamical information (decay time, etc.)
allows derivation of physical characteristics of flaring
regionFlaring plasma must be magnetically confined, thus this
allows to measure the size of individual magnetic structures
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S. Sciortino – Ringberg 11.03.2005
Example: solar flares
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S. Sciortino – Ringberg 11.03.2005
Some math...
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S. Sciortino – Ringberg 11.03.2005
Temperature-density evolution of solar flares
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S. Sciortino – Ringberg 11.03.2005
What if decay is not free?
Equation for L assumes that one measures the intrinsic decay
time scale of loopIf heating is present during decay, τlc >
τth
The loop will appear longer than it isThe slope ζ of the flare
decay in the log(T)-log(n) diagram is a sensitive diagnostic of the
presence of significant heating
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S. Sciortino – Ringberg 11.03.2005
Results from past flare analyses
Large number of intense flares analyzed with this technique:
RS CvnAlgol systemsFlare starsYoung solar-type stars
Invariably L R* : flaring structures are small and confined to
the immediate photospheric surroundings
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S. Sciortino – Ringberg 11.03.2005
Enter the Orion Nebula Cluster Chandra observation (COUP)13 days
non-stop observation
Except for orbit gaps every 48 hrUnique opportunity to study
long-lasting flaring eventsUnique opportunity to measure the size
of magnetic structures in accreting YSOs1600 X-ray sources
detected32 flares with sufficient statistics for detailed
analysis
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S. Sciortino – Ringberg 11.03.2005
Analysis of COUP flares
COUP 1343, results:long lasting (τ ≈40 ks)very hot plasma (100s
MK)almost free decay fast temperature decay steep ζLong loop 2 ×
1012 cm (≈ 0.1 AU!)Confining B field 150 G
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S. Sciortino – Ringberg 11.03.2005
Analysis of COUP flares
COUP 28, results:very long lasting (τ ≈80 ks)moderate T plasma
(≤100 MK)sustained heating slow temperature decay shallow ζLongish
loop 1 × 1012 cm (L/2 ≈ 2.5 R*)Confining B field 180 G
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S. Sciortino – Ringberg 11.03.2005
How can these long loops be structured?
Never seen in more evolved starsStability problem respect to
centrifugal force
Orion YSOs are fast rotators (P ≈ 3-6 d)Co-rotation radius
typically at 3-4 R*Long loops anchored on star only would be ripped
open
Solution: loops connecting star and disk (at corotation
radius)
Postulated by magnetospheric accretion scenario
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S. Sciortino – Ringberg 11.03.2005
Magnetospheric accretion
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S. Sciortino – Ringberg 11.03.2005
Flaring structures in ONC YSOs
Study of flaring structures in ONC YSOs has provided direct
evidence of long magnetic structures in YSOsFirst “direct”
determination of their size and B value
Extrapolation to photosphere compatible with Zeeman-measured
fields (up to 5-6 kG)
Also, smaller ('normal coronal') structures present as shown
from firm detection of X-ray rotational modulation in YSOs
(Flaccomio et al. 2005, ApJS in press)Hint that large flaring
structures present only in non-accreting systems (but statistics is
limited ...)
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S. Sciortino – Ringberg 11.03.2005
R Corona Australis SFR in X-rays
@ 170 pcThe six blue sources are protostars seen with
XMM-Newton
Hamaguchi et al. 2005, ApJ in press
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S. Sciortino – Ringberg 11.03.2005
The same YSOs seen in X-rays and infrared light. N
H ~ 3 10^23, Av ~ 180 m
XW
counterpart of IRS7 X
E: no counterpart down to
K ~19.4 m / Class O I If X-rays from Class 0
confirmed as a general occurrence Magnetic effects become an
essential ingredient for understanding star formation process.
Magnetic field structures can moderate the cloud collapse
X-ray from a Class 0 YSO ?
XE
XW
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S. Sciortino – Ringberg 11.03.2005
Summary
X-rays provide new, unique diagnostics of YSOs physicsDisk
heating, chemistry, orientation
FluorescenceSize and location of magnetic structures funnelling
accreting plasma
Flare analysisX-rays from Class 0 imply a key role of magnetic
field in regulating star formation processPhysics and structure of
accretion stream
He-like triplet study