A (short) review of the talks
and posters presented
Randall Smith
JHU & NASA/GSFC
Spectroscopy puts most of the
“physics”
into X-ray astrophysics
– Claude Canizares
1895 ApJ, 1, 1:
A. A. Michelson on
how to measure
spectral lines
emitted in solar
prominences
“Synthesize, don’t
Summarize”
•
•
•
•
•
Methods & Models
Accretion (WA, Fe K)
Stars – flares & FIPs, O (-type) my!
Expect the Unexpected
Future of X-ray Spectroscopy
What didn’t we talk about?
(much)
• SNRs (except Dewey) – and we clearly
need to re-observe Cas A in 6-7 years
• Clusters (except Peterson, Behar) –
although absence of cooling flows a
blockbuster; also found vturb<30 km/s
with a 300 km/s spectrometer!
What didn’t we talk about?
(much)
• SNRs (except Dewey) – and we clearly
need to re-observe Cas A in 6-7 years
• Clusters (except Peterson, Behar) –
although absence of cooling flows a
blockbuster; also found vturb<30 km/s
with a 300 km/s spectrometer!
We need non-dispersive X-ray
spectra!
Methods & Models
Some things are easy. [Thank
goodness!]
– Identifying ion parent of (most) lines
• Fe L shell lines easy to id; strengths harder
• RRC features mostly easy to id as well.
– Doppler shifts (if  known well; need lab
data!)
• But getting v to 3.7 km/s in EX Hya impressive
– Diagnostic line ratios of (strong) lines
• But watch out for LOS differences in models!
Methods & Models
Others are hard
– Fitting high-resolution broad band spectra
– Measuring a faint continuum
– Determining an Emission or Absorption
Measure Distribution (EMD, AMD)
– Creating a model simple enough to
calculate but powerful enough to
encapsulate data
Methods & Models
Are we ready for a satellite which produces
nothing but high-resolution X-ray spectra?
HETGS
LETG
ACIS
GTO
GO
GTO
GO
GTO
GO
All
>50 ksec
164
338
40
114
1147
3818
54
124
21
52
69
469
(33%)
(37%)
(53%)
(46%)
(6%)
(12%)
Methods & Models:
Analyzing high-resolution spectra
• RGS, HETG, and LETG spectra all have
more resolution elements than this projector!
• Methods: Which converge? to the right
value?
–
–
–
–
–
–
“Photon Clean,” including bootstrap
Line-Based Analysis
absline
Gaussian fits after continuum determination
Adding components until 2 stops dropping
Continuum finding: find line-free regions, assumed
power-law, spline fit, other method?
• What constitutes a “good” fit?
Methods & Models:
Analyzing high-resolution spectra
• RGS, HETG, and LETG spectra all have more
resolution elements than this projector!
• Methods: Which converge? to the right value?
–
–
–
–
–
–
“Photon Clean,” including bootstrap
Line-Based Analysis
absline
Gaussian fits after continuum determination
Adding components until 2 stops dropping
Continuum finding: find line-free regions, assumed powerlaw, spline fit, other method?
Methods & Models:
Analyzing high-resolution spectra
Is the biggest problem:
– atomic data? (20-30% correlated
errors)
– calibration? (3-15% correlated errors)
– insufficient counts (what metric?)
– methodology? (unknown...)
Methods & Models
• Accessing data getting easier:
– BiRD for XMM RGS data
http://xmm.esac.esa.int/BiRD/
– XATLAS for HETG stellar data
http://cxc.harvard.edu/XATLAS
– Profit for GUI spectral viewing
• with ATOMDB or XSTAR line ids!
http://heasarc.gsfc.nasa.gov/software/profit
(+ CIELO for RGS/Sy1.5+, HotGAS for HETGS)
Accretion: Introduction
• Ubiquitous process
– SMBH
– Galactic BH
– X-ray (NS) binaries
– WD (CVs: baby Seyferts that become SSS
when the corona collapses...)
• Dynamic!
(Winds,
WA,
etc)
.
.
• M, Macc, Mwind, Router, Rinner, Spin
– Inclination, Magnetic geometry
Accretion: Questions, Asked or Answered
• RRCs prove photoionization is the dominant
process in some parts of accretion flows.
• Broad Fe K lines in some AGN are real
– But can we really measure the BH spin?
• Soft X-ray excess coincides with optical NLR
• WA: Clumpy or a continuous distribution?
– Can we tell? Are models holding us back, or
calibration, or the data?
– Some X-ray components match UV ones (e.g
NGC 7469), and they respond to changes in the
source flux.
Accretion: Questions, Asked or Answered
• Hot Absorbers at High Velocities
– Do they exist? Are we missing a giant component
of mass outflow?
– Regardless, X-ray observations show this
component dominates UV flows ( > 90%) for
nearby AGN.
• NELG spectra not so flat ( ~ 1.7-1.8, not
1.4), no disk reflection seen (NGC 2110,
3C445)
Stars: Flares & FIPs O (-type)
My!
• Static loop models have DEM  T1.0-1.5
• Observations show DEM  T4.0
– Which agrees with dynamic loop models
– Flares in X-ray may be in optical or not
– Abundances can change during flare.
• CTTS seem to show accretion as well
• Weak Fe K seen in HR 9024 flare; reflection
model agrees with loop geometry.
Stars: Flares & FIPs
• (I)FIP is
– Solved
– Mysterious
– Unexplained
Stars: Flares & FIPs
• (I)FIP is
– Solved
– Mysterious
– Unexplained
– Confusing all those not working in stars...
Hot Stars:
Controversy in the offing?
O star lines are broad & symmetric(ish)
– Resonant scattering?
– Opacity?
– Or from shocked protons & CX, while the
electrons remain cold
Expect the Unexpected
• Measuring dust or molecular composition
– Ferrous vs ferric iron? With X-rays from the Crab
nebula? Yes!
– Main limitation in seeing XAFS is data, both
observational & experimental.
• Did Alpha Cen A disappear? Nope, just got
cooler–side benefit of the LETGS
• X-rays can catch SS433’s jet hitting a bump
• The hot gas seen at z~0 is really in the Galactic
halo.
Future of X-ray Spectroscopy
• Velocity broadened lines detected with
suggestion of both cold and collisional
plasmas in the LLAGN M81; need resolution,
EA!
• Detect redshifted iron lines from surface of
NS, determine EOS; need ...
• Track material falling into AGN via Fe K;
need...
Future of X-ray Spectroscopy
• Velocity broadened lines detected with
suggestion of both cold and collisional
plasmas in the LLAGN M81; need resolution,
EA!
• Detect redshifted iron lines from surface of
NS, determine EOS; need ...
• Track material falling into AGN via Fe K;
need...
• Con-X (and CAT) can give resolution, EA
The
Unified
AGN
Spectrum:
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
NGC 3783!