Download X-ray effects on protoplanetary disks

X-ray effects on protoplanetary disks
Eric Feigelson
(Penn State University)
1. Review of X-ray flaring from YSOs
2. Evidence for X-ray irradiation of disks
3. Consequences of X-ray irradiation
Theme
We see how stellar magnetic fields
can influence disk magnetic fields
through the high-energy radiation
of violent reconnection events
Chandra Orion Ultradeep Project
13 days nearly-continuous observation in 2003
22 papers, 2005-08
(Getman et al. 2005)
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Solar/stellar X-rays arise from magnetic
reconnection events of fields erupted
from the stellar interiors
X-ray Sun -- Yohkoh
Yokohama & Shibata 1998
Theoretical calculations of pre-main sequence magnetospheres
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Donati et al. 2007, Jardine et al. 2006
Long et al. 2007, Romanova et al. 2008
Magnetically funneled accretion on open field lines
Magnetic reconnection flares from closed field lines
X-ray flares are strong and ubiquitous in
pre-main sequence stars throughout the
planet formation era
• Elevated X-ray flaring seen in thousands of PMS stars in
dozens of star forming regions. 28 < log Lx < 32 erg/s.
• For 1 MO stars, flares are ~102 more luminous and ~102 more
frequent than in contemporary Sun.
• X-ray flare levels strongly correlated with stellar mass, Lx~M1.8
Not correlated with rotation (Fossil field? Magnetosphere
truncation? Convective dynamo saturation?)
• X-ray flare levels rise slightly from Class I-II-III phases,
(t~105-107 yrs), and decay during main sequence
(t~108-1010 yrs). Not convincingly seen in Class 0, but
likely present.
Feigelson et al. (2007) PPV review. Studies include:
Wolk et al. (2005), Preibisch et al. (2005), Preibisch & Feigelson (2005), Telleschi et al. (2007),
Stelzer et al. (2007), Giardino et al. (2007), Carramazza et al. (2007), Prisinzano et al. (2008)
X-ray spectrum of a high-Lx Orion star
10 keV
5 keV
1 keV
Note that pre-2000 studies showed only <2 keV
due to poor telescopes. Chandra/XMM see <8 keV
and models sometimes infer X-rays out to 15-20 keV.
Maggio et al. 2007
Some T Tauri flares are extraordinarily hot
and arise in extraordinarily large loops
Orion bright flares
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Superhot flares
Older active stars
Solar flares
Getman et al. 2008a
Loop size / Corotation radius
Evidence for
magnetosphere
confinement by
disk
H-K excess
Getman et al. 2008b
Rarely mentioned ….
Flare X-rays must irradiate disks
The mid-IR spectral energy distribution of YSO disks
requires they be illuminated by photospheric light
giving a `flared’ structure.
Chiang & Goldreich 1997; PPV review by Dullemond et al. 2007
As the X-rays are formed above the stellar surface,
geometrically they also should illuminate the disk.
X-ray influence on protoplanetary disks
Mag field lines
Cosmic rays
Flare X-rays
Proto-Jupiter
Proto-Earth
Flare MeV particles
Dead zone
Feigelson 2003, 2005, 2010
Ionized MHD
turbulent zone
Typical model of a disk with X-ray irradiation
Ilgner & Nelson 2006abc
Density
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Ionization: X-rays penetrate to
midplane outside ~1-5 AU
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Evidence that stellar X-rays
irradiate protoplanetary disks
1.
Some systems show soft X-ray absorption attributable
to gas in the disks
2.
Some systems show evidence of reflection of X-rays off
of the disk: the fluorescent 6.4 keV iron line
3.
Some disks show [NeII] 12.8m line from X-ray
ionization
4.
Many disks show a non-equilibrium hot molecular layer,
excited H2, H2O and CO from X-ray or UV irradiation
X-ray absorption by gas
in edge-on Orion proplyds
Kastner et al. 2005
Iron fluorescent line
Cold disk reflects flare X-rays
YLW 16A: protostar in Oph
Tsujimoto et al. 2005, Favata et al. 2005,
Giardino et al. 2007, Skinner et al. 2007,
Czesla & Schmitt 2007
Review by Gudel & Naze 2009
Imanishi et al. 2001
Stellar X-rays ionize and heat
outer disk atmospheres
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[Ne II] 12.81 m line predicted
Glassgold et al. 2006; Meijerink et al. 2008;
Ercolano et al. 2008/9/10; Alexander 2008;
Gorti & Hollenbach 2008; Glassgold et al. 2009;
Schisano et al. 2010; Shang et al. 2010;
Owen et al. 2010
[Ne II] line detected with Spitzer and 8m telescopes
Pascucci et al. 2007; also Lahuis et al. 2007; Herczeg et al. 2007; Najita et al. 2009/10;;
Flaccomio et al. 2009; Pascucci & Sterzik 2009
Hot CO and H2O seen in some PPDs
CO
H2O
Carr et al. 2004
X-rays are the principal source
of disk ionization
YSO X-ray ionization rate dominates CRs in the
disk by 108 for 1Mo PMS star at 1 AU:
z = 6x10-9 (Lx/2x1030 erg s-1) (r/1 AU)-2 s-1
The ionization fraction is uncertain due to
recombination processes. Hard (5-20 keV) X-rays
should penetrate 1-100 g/cm2.
Igea & Glassgold 1997 & 1999; Fromang, Terquem & Balbus 2002;
Matsumura & Pudritz 2003/6/8/9; Alexander, Clarke & Pringle 2004;
Salmeron & Wardle 2005; Ilgner & Nelson 2006abc; Turner et al. 2009/10;
Ercolano et al 2009/10;
Reviews: Glassgold et al. 2000 & 2006; Balbus 2003
Theorists modeling ionized disks
are strongly encouraged to use …
realistic broad-band X-ray spectra,
realistic range of X-ray luminosities,
and (when relevant) realistic X-ray variability
also please mention role of X-rays
as likely principal source of disk ionization
with reference to the data
Plausible X-ray/flare effects
on protoplanetary disks
• PMS X-ray ionization will heat gas and change
chemistry in disk outer layers
Aikawa & Herbst 1999 and dozens of studies
• PMS X-rays may be an important ionization source at
the base of bipolar outflows
Shang et al. 2002 and a few studies
• X-ray ionization is likely to induce MRI turbulence
affecting accretion, dust coagulation, protoplanet
migration, gaps
Glassgold et al 1997 and dozens of studies
• Flare energetic particles and shocks may explain
meteoritic mysteries (chondrule melting, short-lived
radionuclides)
Shu et al. 1997 and a few studies
Conclusions
• The X-ray studies of young stars show that powerful
magnetic flares are ubiquitous throughout the epoch of
planet formation, 103 above solar levels. The
astrophysics resembles gigantic solar flares.
• X-rays can efficiently irradiate protoplanetary disks.
X-ray evidence:
IR evidence:
Fe fluor lines Absorption
[NeII] line
Mol. excitation
Possible consequences
on planet formation
processes:
MRI, turbulence, viscosity, etc
Gas heating & ion-molecular chemistry
Ionization of outflows
Spallation of isotopes, chondrule melting