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Universita` di Palermo fabio.reale@unipa - cosmos.esa.int · Accretion impacts studied on the Sun...
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Accretion impacts studied on the Sun Fabio Reale Dipartimento di Fisica e Chimica Universita` di Palermo [email protected] The X-ray Universe 2014 Trinity College Dublin, Ireland 16th - 19th June 2014
Transcript of Universita` di Palermo fabio.reale@unipa - cosmos.esa.int · Accretion impacts studied on the Sun...
Accretion impacts studied on the Sun
Fabio Reale Dipartimento di Fisica e Chimica Universita` di Palermo [email protected]
The X-ray Universe 2014 Trinity College Dublin, Ireland 16th - 19th June 2014
Accretion flows on young stars (T Tauri)
Accretion in YSO
! Disk-star: magnetic funnels (Königl 1991)
! Accretion flows: V≫100 km/s ! Impact: IR/V/UV excess (Bertout+
1988, Natta+ 2006, Herczeg & Hillenbrand 2008, Donati+ 2008)
! +Soft X-ray excess (Chandra, XMM-Newton): dense (1011 − 1013
cm−3) and hot (2-4 MK) plasma (Kastner+ 2002, Argiroffi+ 2004, 2007, Schmitt+ 2005, Guenther+ 2007, Telleschi+ 2007)
Fendt 1995
X-ray Accretion in T Tauri stars
! High density in relatively cool X-ray lines (e.g. NeIX, low f/i ratio)
Argiroffi+ 2004, ApJ, 609, 925.
Accretion impacts
! Models explain the X-ray emission from steady impact shock of continuous accretion column (e.g. Sacco+ 2010)
! Questions: ! Accretion rate: UV/V/NIR ≫ X. Why? ! What is the role of absorption? ! What is the role of stream structuring?
! Concept: use the Sun as a template
Accretion flows: impact region
Accretion flows: impact region
Bright hot impacts by erupted fragments falling back on the Sun: a template for stellar accretion
Fabio Reale (Univ. Palermo) Salvatore Orlando (INAF-OAPa) Paola Testa (Harvard CfA, USA) Giovanni Peres (Univ. Palermo) Enrico Landi (Univ. Michigan, USA) Carolus (Karel) J. Schrijver (LMSAL, USA)
The flare and the eruption: 7 June 2011 Tanaka+ 2011 Li+ 2012 Innes+ 2012 Muraki+ 2012 Cheng+ 2012 Williams+ 2013 Inglis & Gilbert 2013 Gilbert+ 2013 Carlyle+ 2014 Dolei+ 2014 van Driel-Gesztelyi+ 2014
The impacts region
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Close up: 171 A (Fe IX, logT~5.9)
Data analysis
! Impacting plasma: ! Density: 2 < n < 10 x 1010 cm-3 (from
absorption) ! Velocity: 300 < v < 450 km/s (from images
and STEREO data) ! Size: r~2000-4000 km, l~2000-10000 km
! Weak magnetic field (β≫1, SDO/HMI)
! Free fall (STEREO)
Landi & Reale 2013
Hydrodynamic simulations
! Hydrodynamic model of plasma blobs downfalling in a tenuous (108 cm−3) corona (~1 MK) ! Impact speed: 400 km/s ! Density: 5 × 1010 cm−3 (T~2000 K)
! 2D cylindrical geometry ! Spatial resolution: 5 km ! Radius: 2000 km ! FLASH code (Fryxell+ 2000)
Train of droplets
Density Temperature
Train of droplets: 171 A emission
! EUV emitting plasma: 7%
Cross-section Integrated
We match the observation….
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Quantitative agreement: Light curves
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Model Data
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Hints/results stars vs Sun
! Density: 1011−1013 cm−3
! Velocity: 400-500 km/s
! Temperature: 2 – 4 MK ! Accretion rate:
! Total: 10-11- 10-7 M"/yr
! X-rays: 10-10- 10-9 M"/yr
! ?
! Density: 5 1010 cm−3
! Velocity: 300-450 km/s
! Temperature: ~1 MK ! (Accretion rate: 10-14 M"/yr)
! Absorption -> Emitting mass: 5-25%
! Emission from disk material
! Role of fragmentation
Stars: X-rays Sun: EUV
Conclusions
! Sun as a small-scale benchmark for accretion in YSO in EUV and X-rays ! Insight: Impact evolution and mechanisms ! New hints: role of absorption (see talk by S. Bonito) ! New hints: emission from disk material ! New hints: fragmentation ! New hints: Doppler shifts
! Template for other phenomena? (e.g. funnelled flows)
