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 papers, (Getman et al. 2005)

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 Donati et al. 2007, Jardine et al Magnetically funneled accretion on open field lines Magnetic reconnection flares from closed field lines Long et al. 2007, Romanova et al. 2008

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 L x < 32 erg/s. For 1 M O stars, flares are ~10 2 more luminous and ~10 2 more frequent than in contemporary Sun. X-ray flare levels strongly correlated with stellar mass, L x ~M 1.8 Not correlated with rotation (Fossil field? Magnetosphere truncation? Convective dynamo saturation?) X-ray flare levels rise slightly from Class I-II-III phases, (t~ yrs), and decay during main sequence (t~ 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-L x Orion star 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 keV. 1 keV 5 keV10 keV Maggio et al. 2007

Some T Tauri flares are extraordinarily hot and arise in extraordinarily large loops Solar flares Older active stars Orion bright flares Superhot flares Getman et al. 2008a

Evidence for magnetosphere confinement by disk Getman et al. 2008b Loop size / Corotation radius H-K excess

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 As the X-rays are formed above the stellar surface, geometrically they also should illuminate the disk.

Dead zone Ionized MHD turbulent zone Cosmic rays Flare X-rays Flare MeV particles Mag field lines Proto-Jupiter Proto-Earth Feigelson 2003, 2005, 2010 X-ray influence on protoplanetary disks

Typical model of a disk with X-ray irradiation Ilgner & Nelson 2006abc Density Ionization: X-rays penetrate to midplane outside ~1-5 AU

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 H 2, H 2 O 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 Tsujimoto et al. 2005, Favata et al. 2005, Giardino et al. 2007, Skinner et al. 2007, Czesla & Schmitt 2007 Review by Gudel & Naze 2009 YLW 16A: protostar in Oph Imanishi et al Best case!

Stellar X-rays ionize and heat outer disk atmospheres [Ne II]  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 [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 H 2 O seen in some PPDs Carr et al H2OH2O CO

X-rays are the principal source of disk ionization YSO X-ray ionization rate dominates CRs in the disk by 10 8 for 1M o PMS star at 1 AU:  = 6x10 -9 (L x /2x10 30 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 g/cm 2. 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 & 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 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 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, 10 3 above solar levels. The astrophysics resembles gigantic solar flares. X-rays can efficiently irradiate protoplanetary disks. X-ray evidence:Fe fluor linesAbsorption IR evidence:[NeII] lineMol. excitation Possible consequencesMRI, turbulence, viscosity, etc on planet formationGas heating & ion-molecular chemistry processes: Ionization of outflows Spallation of isotopes, chondrule melting