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X-rays and planet formation. X-rays from young stars Magnetic reconnection flaring Some results from COUP & XEST Do X-ray flares influence planet formation? Evidence for X-ray irradiation of disks Implications of flare irradiation. Eric Feigelson (Penn State).

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x rays and planet formation

X-rays andplanet formation

  • X-rays from young starsMagnetic reconnection flaring
  • Some results from COUP & XEST
  • Do X-ray flares influence planet formation?
  • Evidence for X-ray irradiation of disks
  • Implications of flare irradiation

Eric Feigelson (Penn State)

From Stars to Planets Apr 2007


X-rays and star/planet formation

Orion Nebula cluster & proplyd

Star formation occurs in molecular cloud cores at T~10-100 K. Planet formation occurs in disks at T ~100-1000 K. This is neutral material (meV).


But high energy radiation is present in planet formation environments: keV photons & MeV particles are produced in violent magnetic reconnection flares.

Does this influence disk processes?

(heating, ionization, chemistry, turbulence, viscosity, shocks, melting & spallation of solids)

Theory looks good

Is there evidence for X-ray/flare effects in disks, extrasolar planets & meteorites?

Fe 6.4 keV & NeII 12.81mm, meteorites

some useful references
Some useful references
  • X-rays from young stars & stellar clusters

Protostars & Planets V review article 2007

Feigelson, Townsley, Guedel & Stassun

  • ~20 papers from COUP

ApJ Suppl Special Issue October 2005 + others 2006-07

  • ~15 papers from XEST

Special Issue As&Ap 2007

  • ~5 papers/month on X-rays SFRs & disks

The Chandra Orion

Ultradeep Project

13-day observation

of the Orion Nebula

1616 COUP sources:

849 low-NH ONC stars

559 high-NH stars, incl.

75 new members

16foreground stars

159 probable AGN

23 uncertain

Getman & 22 others 2005 COUP #1 & #2

extraordinary flares in orion pre main sequence stars
Extraordinary flares inOrion pre-main sequence stars



JW 738


Age ~ 10 Myr

Mass ~ 1 Mo

log Lp = 32.6 erg/s

X-ray cts / ks

Time (13.2 days)

Wolk et al. 2005 COUP #5


X-ray luminosity fn

spans 28 < logLx < 32 erg/s

Correlation with stellar mass plus scatter

There is no X-ray

quiet population for

M<3 Mo

All X-ray sources are

dominated by flares

Guedel et al. XEST #1

characteristics of pms flaring
Characteristics of PMS flaring
  • Orion flares are typically 102 stronger than >X9 solar
  • flares releasing 1035-1036 ergs (0.5-8 keV). Many
  • smaller flares (powerlaw distribution like Sun/stars).
  • Flares occur every few days and last ~2-20 hrs
  • Flares unrelated to accretion variations and are
  • independent of presence of disks
  • Flare lightcurve & spectral evolution are usually
  • similar to solar/stellar flares
  • X-ray energies often extend to >10 keV

Pre-main sequence X-rays are generally not

produced by the accretion process

~15-day light curve

X-ray flares

Optical accretion event

No relation seen between X-ray flares and accretion variations in ~800 Orion stars. Stassun et al. 2006/7 COUP #15/16

No difference in X-ray flaring of ~100 Class II vs. Class III Taurus stars.

Stelzer et al. XEST #11

solar stellar x rays arise from magnetic reconnection events in the corona
Solar/stellar X-rays arise from magnetic reconnection events in the corona

X-ray Sun -- Yohkoh

Yokohama & Shibata 1998

t tauri x rays arise from a complex reconnecting magnetosphere
T Tauri X-rays arise from a complex reconnecting magnetosphere

Both smaller (<1 R*) and giant (~10 R*) loops are inferred from COUP

Flaccomio et al. 2005 Favata et al. 2005 COUP #6 & 7

Open accreting

field lines

Closed plasma-filled

field lines

Resulting X-ray corona

(without flares)

Jardine et al. 2006


X-ray emission elevated throughout planet formation epoch

1 Mo

X-ray levels are

roughly constant

during Class I-II-III


but drop greatly on

the main sequence

0.5 Mo

0.2 Mo

Preibisch & Feigelson 2005 COUP #4

three lines of evidence that x rays irradiate protoplanetary disks
Three lines of evidence that X-rays irradiate protoplanetary disks
  • Some systems show evidence of X-ray reflection off of the disk: the fluorescent 6.4 keV iron line

Imanishi et al. 2001, Tsujimoto et al. 2005, Favata et al. 2005

  • Some systems show soft X-ray absorption attributable to gas in the disks Kastner et al. 2005
  • Some systems show [NeII] IR line

Glassgold et al. 2006, Pascucci et al. 2007

iron fluorescent line cold disk reflects flare x rays
Iron fluorescent lineCold disk reflects flare X-rays

COUP spectra

YLW 16A: protostar in Oph

Imanishi et al. 2001

Tsujimoto & 7 others

2005 COUP #8

x ray absorption by gas in edge on orion proplyds
X-ray absorption by gas in edge-on Orion proplyds

First measurement

of gas content of




Kastner & 7 others

2005 COUP #9

x ray influence on planet formation
X-ray influence on planet formation

Mag field lines

Cosmic rays

Flare X-rays



Flare MeV particles

Dead zone

Ionized MHD

turbulent zone

Feigelson 2003, 2005

x rays disk ionization
X-rays & 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 (5-15 keV) X-rays should penetrate 1-100 g/cm2.

Igea & Glassgold 1997 & 1999; Fromang et al. 2002; Matsumura &

Pudritz 2003 & 2006; Alexander et al. 2004; Salmeron & Wardle 2005;

Ilgner & Nelson 2006; Glassgold et al. 2007; Nomura et al. 2007

Reviews: Glassgold et al. 2000 PPIV & 2006; Balbus ARAA 2003;

Dutrey et al. PPV 2007; Bergin et al. PPV 2007

plausible x ray flare effects on protoplanetary disks
Plausible X-ray/flare effects on protoplanetary disks
  • PMS X-ray ionization will heat gas and change chemistry in disk outer layers.
  • PMS X-rays may be an important ionization source at the base of bipolar outflows.
  • X-ray ionization is likely to induce MRI turbulence affecting accretion, planetesimal formation, migration, ...
  • Flares may help explain enigmas in the meteoritic record: short-lived radionuclides, chondrule flash melting

X-ray ionization of the gaseous disk


Atomic excitation calculation of J1/2 J3/2 [NeII] 12.81 mm line from ionized outer layer of disks around 5-10AU

Glassgold et al. 2006


Spitzer FEPS Legacy reports [Ne II] line in 4 older, X-ray

bright T Tauri stars

Pascucci et al. 2007

protoplanet migration in a turbulent disk
Protoplanet migration in a turbulent disk

X-rays  MRI  MHD turbulence  inhomogeneities producing

gravitational torques which overwhelm the Goldreich-Tremaine torque,

so protoplanets undergo random walks rather than secular Type I

migration. Gap formation suppressed.

Laughlin et al. 2004 and other groups

  • The X-ray studies of young stars show that powerful magnetic flares are ubiquitous throughout the epoch of planet formation. The astrophysics resembles solar flares
  • X-rays can efficiently irradiate protoplanetary disks

Evidence: Fe fluor lines Absorption


consequences: Ionization Turbulence

Heating Chemistry

Chondrule melting Outflows

CAI isotopes

Therefore …..


Planetary systems form in

cool dark disks


which are irradiated by 10 8violent

magnetic reconnection flares