Young Stellar Objects from Soft to Hard X-Rays - APC

Our principal questions for protostars:!-# What is the high-energy environment of protostars?"-# Are magnetic fields present, and how are they generated (dynamo, fossil)?!-# Are there magnetic fields between star and disk, responsible for!!angular momentum transport!! mass accretion from disk to star!! perhaps jet launching?!- When do we see first evidence for these features?!2nd Simbol-X Symposium Paris Dec. 2008!(Montmerle et al. 2000)!

Problem: Absorption!Protostar!N H = 6.6x10 22 cm -2!(A V " 33 mag)!non-accreting TTS!N H = 3.1x10 21 cm -2!(A V " 1.5 mag)!accreting TTS!N H = 1.4x10 22 cm -2!(A V " 7 mag)!Problem: Strong photoelectric absorption in protostars!2nd Simbol-X Symposium Paris Dec. 2008!

Protostars, High-Enery Radiation and Particles, and Magnetic Fields!Class I: N H > 10 22 cm -2 $ 50% detected in surveys of nearby YSOs !1.# Emission is very hard;!! average T decreases I ! II ! III !! (Ozawa et a. 2005, Telleschi et al. 2007,!! Giardino et al .2007; bias possible:!!Prisinzano et al. 2008) !kT (keV) !(Prisinzano et al. 2008)!2. !Strongly developed Fe K lines:!!Magnetic heating. !2nd Simbol-X Symposium Paris Dec. 2008!(Imanishi et al. 2001)!

5. !Nonthermal radio emission in Class I:!Radio gyrosynchrotron !!accelerated (MeV) electrons!closed magnetic fields!(also in the jets)!(e.g., Ray et al. 1997; Smith et al. 2003)!circularly!polarized bursts!(Ray et al. 1997)!2nd Simbol-X Symposium Paris Dec. 2008!(Smith et al. 2003)!

Class 0: N H > 10 23 cm -2 (typically); X-ray candidates, no clear-cut case !So far only detections of !sources with uncertain/debated !Class 0 status!(Tsuboi et al. 2001, Hamaguchi et al.!2005, Getman et al. 2006)!Six stacked Class 0 observations:!non-detection.!(Giardino et al. 2007)!What are N H , kT, L X ? !(6 stacked observations; Giardino et al. 2007)!2nd Simbol-X Symposium Paris Dec. 2008!

2nd Simbol-X Symposium Paris Dec. 2008!

High-Energy Photons from the Sun!XMM, Chandra!thermal X-rays!nonthermal !hard X-rays:!e-bremsstrahlung!10 keV – MeV!electrons! 20 MeV- GeV protons, !neutrons, nuclei!nuclear lines:!energetic ion collisions!(Lin et al. 2002)!2nd Simbol-X Symposium Paris Dec. 2008!pion decay!(Lin et al. 2002)!

Flares: Energy Release by Magnetic Reconnection!Unified flare model:!A explains Standard ! Solar Flare Scenario!•# place filament of action:! eruption!•# •# mass heating! ejection!•# •# flare shock proper! formation!•# particle acceleration!at once!2nd Simbol-X Symposium Paris Dec. 2008!(Shibata 1999)!

Standard flare scenario after reconnection!0. Reconnection ! particle acceleration2. RadioSynchrotron3. Prompt Hard-X& optical bursts!#1. Electrons6. Soft X-Rays5. Evaporationof hot plasma2nd Simbol-X Symposium Paris Dec. 2008!4. Heating !overpressure ! massmotion

U band!Soft X!Proxima Centauri!Hard X!(20-60 keV)!(Güdel et al. 2002, 2004)!Sun:!White !Light!2nd Simbol-X Symposium Paris Dec. 2008!(Hudson 1993)!

Impulsive Soft X-Rays or Non-Thermal Hard X-Rays?!2nd Simbol-X Symposium Paris Dec. 2008!(Güdel et al.)!

soft!Nonthermal HXR?!Stellar flare seen by SWIFT: !$#= 2.8 - 3.1 (electron distribution;!like in solar flares)!hard!Power-law?!(superhot, thermal component !cannot be excluded)!(Osten et al. 2007)!2nd Simbol-X Symposium Paris Dec. 2008!

Orion Young Stellar Object:!Fluorescence!6.4 keV line during impulsive!phase like HXR or radio!(Osten et al. 2007, Czesla &!Schmitt 2007):!K shell electron ejection by!nonthermal electrons? !SXR flare!(challenged by Drake et al. 2008)!6.4 keV!Need hard X-rays to !unambiguously decide.!Czesla & Schmitt 2007)!2nd Simbol-X Symposium Paris Dec. 2008!

Model!PL: $ = 3!What Simbol-X Will See - I:!II Peg flare (Osten et al. 2007)!with non-thermal power law!L X = 1.3x10 33 erg s -1 (= 0.24 L ! )!distance = 42 pc!3 ks!30 sec (!)!“3 ks in Orion (400 pc)”!2nd Simbol-X Symposium Paris Dec. 2008!

Evidence for Stellar High-Energy Particles!radio-strong !brown dwarfs!(Berger 2006, Güdel & Benz 1993)!2nd Simbol-X Symposium Paris Dec. 2008!

Solar Guidance!Dynamic non-potential fields:!Many unstable places where !reconnection proceeds!2nd Simbol-X Symposium Paris Dec. 2008!

Smallest Stellar Flares Seen in X-Rays: Proxima Centauri!Gradual!phase:!Coronal!heating after!evaporation!soft X-raysUVImpulsive!phase:!Reaction!to particle!flux? !2nd Simbol-X Symposium Paris Dec. 2008!(Güdel et al. 2002)!

Flare Energy Distributions!dN/dE % E -&L X % ' E dN/dE dEE1E2&# ( 2: divergence forE1 ! 0("microflares")log(dN/dE)% E -&logEIn that case, all of the observed (quasi-steady) emission!"may be" due to the superposition of small flares!2nd Simbol-X Symposium Paris Dec. 2008!

dN/dE % E -& & " 2.2 +/- 0.2 !Figures from Audard et al. 1999E (0.01-10 keV)!2nd Simbol-X Symposium Paris Dec. 2008!(Audard, Güdel, Guinan 2000)!

dN/dE % E -& !Collura et al. 1988 !& " 1.52 ± 0.08 !M dwarfs!Pallavicini et al. 1990 !& " 1.7 ± 0.1 !M dwarfs !Osten et al. 2000 !& " 1.6 !RS CVn!Audard et al. 1999, 2000 !& " 2.2 ± 0.2 !G,K,M dwarfs!Kashyap et al. 2002 & " 2.0-2.7 M dwarfsGüdel et al. 2003 & " 2.0-2.5 AD LeoArzner & Güdel 2004 & " 2.3 ± 0.1 AD LeoWolk et al. 2005 & " 1.7 TTS (Orion)Arzner et al. 2007 & mostly 2-5 !TTS (Taurus)Stelzer et al. 2007 & " 2.4 ± 0.5, 1.9 ± 0.2 TTS (Orion, Taurus)Caramazza et al. 2007 & " 2.2 ± 0.2 TTS (Orion)Albacete-Colombo 2007 & " 2.1 ± 0.2 !TTS (Cygnus)2nd Simbol-X Symposium Paris Dec. 2008!Should stellar coronal models really be !(stochastic-) flare models?!

Model!What Simbol-X Will See - II:!PL: $ = 3!300 stars like BP Tau in Taurus,!PL added: & = 2.4, !exposure time 200 ks !distance of Taurus!Method:!1) dN/dE, & = 2.4!2) correct quiescent soft L X !3) Solar HXR/SXR peak!flux relation (Battaglia et al. 2005)!4) e.g.: duration !SXR 3000 s!! ! HXR 1000 s!! Talk by M. Caramazza!PL!2nd Simbol-X Symposium Paris Dec. 2008!

! Conclusions!1.# High-energy particles and photons are key players for the !!ionization and heating of young stellar environments(disks, envelopes): drivers of MRI, chemistry, ...!2.# Deeply embedded objects difficult or impossible to study!! in the soft X-ray range: need hard X-rays.!3. !Hard X-rays from flares and continuous flaring areimportant diagnostics for acceleration process and energybudget of magnetic energy release.!2nd Simbol-X Symposium Paris Dec. 2008!

2nd Simbol-X Symposium Paris Dec. 2008!END!