slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Accretion Processes in X-rays: From White Dwarfs to Quasars Boston, MA 14 July 2010 PowerPoint Presentation
Download Presentation
Accretion Processes in X-rays: From White Dwarfs to Quasars Boston, MA 14 July 2010

Loading in 2 Seconds...

play fullscreen
1 / 19

Accretion Processes in X-rays: From White Dwarfs to Quasars Boston, MA 14 July 2010 - PowerPoint PPT Presentation


  • 115 Views
  • Uploaded on

A New View of Accretion Shock Structure Nancy S. Brickhouse Harvard-Smithsonian Center for Astrophysics Collaborators: Steve Cranmer, Andrea Dupree, Juan Luna, and Scott Wolk. Accretion Processes in X-rays: From White Dwarfs to Quasars Boston, MA 14 July 2010.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Accretion Processes in X-rays: From White Dwarfs to Quasars Boston, MA 14 July 2010' - leda


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

A New View of Accretion Shock StructureNancy S. BrickhouseHarvard-Smithsonian Center for AstrophysicsCollaborators: Steve Cranmer, Andrea Dupree, Juan Luna, and Scott Wolk

Accretion Processes in X-rays: From

White Dwarfs to Quasars

Boston, MA

14 July 2010

accretion shock models t e and n e for given mass accretion rate
Accretion shock models → Te and Ne for given mass accretion rate
  • Kastner et al. (2002) find high Ne in TW Hya
  • ChandraLarge Observing Program to definitively establish accretion as the source of the emission,

and, if confirmed, bring new diagnostics to bear,

using 500 ksec High Energy Transmission Grating

tw hya
TW Hya
  • Classical T Tauri star (accreting)
  • i=7o (pole-on)
  • M = 0.8 MSun
  • R = 0.7 RSun
  • Distance 57 pc
  • 10 million yr old
  • Poised to make planets
  • X-rays from the accretion shock

(Kastner et al. 2002)

  • X-ray plasma has high Neon abundance

(Kastner et al. 2002; Drake, Testa, & Hartmann 2005)

Romanova et al. 2004

accretion and a corona
Accretionand aCorona

Emission Measure

vs Te

Light

curve

Emission measure distribution and variability

allow us to isolate the accretion shock.

Brickhouse et al. 2010, ApJ, 710, 1835

he like line ratio diagnostics
He-like Line Ratio Diagnostics

He-like Energy Levels

Ne and Te Diagnostic Ratios

(Smith et al. 2009)

x ray line ratio diagnostics for density and temperature
X-Ray Line Ratio Diagnostics for Density and Temperature

Ne = 6 x 1012 cm-3 Mg XI

3 x 1012 Ne IX

6 x 1011 O VII

Te = 2.50 ± 0.25 MK

This looks like the accretion shock!

slide10

Neon Region of HETG Spectrum

Spectrum shows strong H-like Ne X and He-like Ne IX,

up to n=7 or 8 in Ne X.

Series lines are sensitive to absorption

complex absorption
Complex absorption
  • O VII: NH = 4.1 x 1020 cm-2
  • Ne IX: NH = 1.8 x 1021 cm-2

Series lines rule out resonance scattering:

Tau ~ g f λ, for a given ion

testing the accretion shock model
Testing the Accretion Shock Model

2GM*

R*

Vff = (1 – R*/rt )1/2

~ 510 km/s

Te = 3.4 MK

Macc = f A*ρpre vff

(Konigl 1991; Calvet &

Gullbring 1998; Gunther et

al. 2007; Cranmer 2008)

testing the accretion shock model1
Testing the Accretion Shock Model

2GM*

R*

Vff = (1 – R*/rt )1/2

~ 510 km/s

Te = 3.4 MK

Macc = f A*ρpre vff

(Konigl 1991; Calvet &

Gullbring 1998; Gunther et

al. 2007; Cranmer 2008)

“Settling”

slide14
Te and Ne from Ne IX agree with the shock model.Model predicts Ne at O VII 7 times larger than observed.
  • Consider a new 2-Region model:
  • Region 1 = the shock front
  • Region 2 = the post-shock region
  • Each region: Ne , Te, NH, V, and M
  • Predict r, i, and f for He-like ions
  • V2 = 300 x V1 => M2 = 30 x M1
slide15
Te and Ne from Ne IX agree with the shock model.Model predicts Ne at O VII 7 times larger than observed.
  • Consider a new 2-Region model:
  • Region 1 = the shock front
  • Region 2 = the post-shock region
  • Each region: Ne , Te, NH, V, and M
  • Predict r, i, and f for He-like ions
  • V2 = 300 x V1 => M2 = 30 x M1

Definitely not “settling”

soft x ray excess ovii ubiquitous
Soft X-ray Excess (OVII) Ubiquitous

Gudel & Telleschi 2007

also see Robrade & Schmitt 2007

accretion variability
Accretion Variability
  • Ne IX diagnostics for 3 observation segments ~150 ksec each give different Te and NH

(Ne does not vary).

  • Variable Te implies changing rin, and thus Mdot
  • Observed diagnostics constrain model Mdot , B, and rout
  • Te varies from 3.1 to 1.9 K
  • Mdot varies a factor of ~5
  • Filling factor varies a factor of ~7
  • rin varies from 1.75 R* to 3.52 R*
  • B varies from 800 to 500 G

Brickhouse et al. 2010, in progress

conclusions
Conclusions
  • High S/N HETG spectrum derives from 3 regions:

a hot 10 MK corona, an accretion shock, and a cool post-shock region.

  • Diagnostics show excellent agreement with simple models of the shock itself.
  • Diagnostics show that standard, one-dimensional models of the post-shock cooling plasma don’t work.
  • Te and NH vary (Ne does not), implying variability in Mdot, B, and rtrunc
  • Our values for Mdot are in good agreement with optical and UV methods.