Transcript A (short) review of the talks and posters presented
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 v turb <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 v turb <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
calculate but
powerful
enough to 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 164 338 40 114 1147
3818
>50 ksec 54 (33%)
124
(37%) 21 (53%)
52
(46%) 69 (6%)
469
(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 power law, 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...) • M, M acc , M wind , R outer , R inner , 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 T 1.0-1.5
• Observations show DEM T 4.0
– 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: NGC 3783!
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