X-ray Spectroscopy of Cool & Warm
Absorbers With Chandra:
From Oxygen to iron
Norbert S. Schulz
1. X-ray Absorption Processes
2. Benefits, Challenges & Future of High
Resolution X-ray Absorption Spectroscopy
3. Cool & Warm X-ray Absorbers:
-Interstellar Media (ISMs) in Galaxies
-Accreting X-ray Binaries
-Active Galactic Nuclei (AGN)
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
1. X-ray Absorption Processes
Photoelectric Continuum Absorption
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
1. X-ray Absorption Processes
Absorption in Cool Matter/Plasmas
Photo-electric continuum absorption
X-ray
fluorescence
Photo-electric 1s-np resonances
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
1. X-ray Absorption Processes
New Models for ISM Absorption
Juett, Wilms, Schulz & Nowak 2006
(tbnew in XSPEC)
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
1. X-ray Absorption Processes
Absorption in Collisionally Ionized Plasmas
Collisional Ionization Equilibrium kT > MK
H-, He-like resonance absorption ( and Li-, B-like for Fe)
Fermi's Golden Rule:
Pi-f = 2p/h |<Ff| W | Fi>|2 r (Ef = Ei)
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
1. X-ray Absorption Processes
Absorption in PhotoionizedPlasmas
Warm absorber:
electron temperature of illuminated matter << 106 K
in contrast to a collisionally ionized gas gas with a
similar level of ionization ( Halpern 1984)
Ionization parameter x = Lx / ned2
C. Reynolds
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
1. X-ray Absorption Processes
XSTAR v2.1 simulations:
Log Lx ~ 37.5 [erg/s], x < 2
Kallman et al. 2004
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
2. Benefits, Challenges & Future of High
Resolution X-ray Absorption Spectroscopy
Chemical evolution and recycling
of matter:
- accurate ccount of matter (nonradiative),
- accretion dignostics,
-inert cool, warm & hot absorbers
in ISM/IGM
Determine matter properties:
optical depths: t(Z)
columns densities: NZ, Nwarm, Nhot
abundance: AZ
composition: elements, molecules
geometry: dx , dt
ionization balance: x, fZ
dust properties/depletion
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Curve of Growth Analysis
Evaluation of measured equivalent width:
-column densities
-line oscillator strengths
-mass dynamics
- linear part
- flat part
- sqrt part
Current Spectral Capabilies
Available Spectrometers: RGS
LETG
HETG
XMM-Newton Dl ~ 0.08 FWHM RGS 1
~ 0.06
RGS 2
Chandra
Dl ~ 0.05 FWHM
Chandra
Dl ~ 0.02 FWHM MEG
~ 0.01
HEG
(CCD have E/dE < 60)
Wavelength range (z=0):
45 A (C-K) -- 1,7 A (Fe K)
Resolving power > 1000 desired
Velocities > 150 km/s resolved
Equivalent Widths ~ mA possible
Resolution vs. Efficiency
l/Dl = 200
Aeff ~ 6000 cm2
l/Dl = 2000
Aeff ~ 1200 cm2
l/Dl = 1200
Aeff ~ 100 cm2
Critical Angle Transmission Gratings
for Con-X
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Phases of Interstellar Media
Phase
n/[ccm]
T/[K]
Cold
30-3000 10-100
Warm 0.03 -0.1 < 10000
Hot
<0.005
< 10 MK
- (Very hot)
Media
MCs, H I
H I, H II
SNR
Diffuse
Chandra HETG ISM Surveys
O-K absorption
Juett et al. 2004
Ne K absorption: Ne II, III, IX
Juett et al. 2006
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Chandra HETG ISM Surveys
O abundance: O II, III
Ne abundance: Ne II, III
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Absorption in X-ray sources
Absorption in collisionally ionized plasmas:
Collisional Ionization Equilibrium kT > MK
H-, He-like resonance absorption ( and Li-, B-like for Fe)
Resonance Absorption in the Hot ISM
NeII Kb
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Future: Absorption Surveys in Galaxies
Principle: backlighting with
bright X-ray continua
Advantage:
Long-range analysis
Entire Galactic plane & Halo
Study all ISM phases
ISM Studies in other Galaxies
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Warm absorbers in Seyfert I galaxies:
Soft absorber in warm plasma:
I. George
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Warm absorbers in Seyfert I galaxies:
X-ray spectra of Active Galactic Nuclei
NGC 3783,
Kaspi et al. 2002
MCG6-30-15,
Lee et al. 2002
Texas Symposium 2006, Dec. 12, Melbourne, Australia
Warm Absorbers in Compact Binaries:
Summary Table:
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Warm Absorbers in Compact Binaries:
Summary Table:
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Hot Absorbers in Compact Binaries:
Summary Table:
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Warm Absorbers in Compact Binaries:
Summary Table:
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Warm Absorbers in Compact Binaries:
EXO 0748+676
Cottam et al. (2003)
Jimenez-Garate, Schulz, & Marshall (2003)
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Warm Absorbers in Compact Binaries:
Microquasars
GRO J1655-40 (Miller et al.2006a)
Cyg X-1 (Marshall et al. 2001, Miller et al. 2005)
Cir X-1 (Brandt & Schulz 2000)
GRS 1915+105
Lee et al. 2002
H 1743-322 (Miller et al. 2006b)
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Warm Absorbers in Compact Binaries:
Microquasars: the special case of Cir X-1
The X-ray binary with two faces:
at high X-ray fluxes (>1 Crab)
Schulz & Brandt (2002)
high ionization parameter: log x > 4
blueshifts: voutflow = 400 -- 2000 km/s
cold and hot absorber present
microquasar
at low X-ray fluxes (<100 mCrab)
Schulz et al. (2007) ApJ, submitted
low ionization parameter: log x = 2 -- 3
no blueshifts
cold, lukewarm, warm absorber present
atol dipper
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA
Summary
1) High resolution (R > 500) X-ray spectrom,eters have opened the window for
absorption spectroscopy as a powerful diagnostic in high energy astrophysics
2) Benefits: line absorption in the X-ray band cover a large range of T [104 -- 107 K],
log x [0.01 -- 5], NH [1019 -- 1024 cm-2];
measure direct abundance & ionization fractions for Z = 6 -- 26
3) Detection of absorption edge structure in O, Fe, Ne;
optical depth measurements for O, Ne, Mg, Si, S, Fe;
first measurments of ionization fractions involving warm ISM phase
4) Detections of cool, warm, hot absorber properties in a large range of objects:
ISM, IGM (WHIM), AGN, LMXBs, HMXBs
5) First detection of an active warm absorber in an accreting NS binary:
Cir X-1 (see also EXO 0748-676)
6) We have met the challenge for more powerful X-ray spectrometers -SO WHERE IS THE NEW MISSION?
X-ray Grating Spectroscopy, July 12, 2007, Cambridge MA, USA