dipartimento di scienze fisiche & astronomiche – universita’ di palermo inaf/osservatorio...

Dipartimento di Scienze Fisiche & Astronomiche – Universita’ di Palermo

INAF/Osservatorio Astronomico G.S. VaianaFabio Reale RESIK,RHESSI &SPIRIT workshop

Wroclaw 6-8 Dec 2005

Emission measure distribution Emission measure distribution from the analysis of coronal from the analysis of coronal

datadataFabio Reale

Dipartimento di Scienze Fisiche & AstronomicheUniversità di Palermo, ItalyE-mail: [email protected]




Summary

DEM of quiescent loops from SoHO/CDS data:Hot active region loopCooler (TRACE) loop: multi-wavelength

DEM of flaring loops from Yohkoh/SXT data




DEM of quiescent loops

History of DEM saga:

Use spectroscopy to derive thermal structure: DEM reconstruction

Wide DEM indicates multi-thermal fibrils, thin DEM monolithic loops

DEM reconstruction shows single line ratios bias (Schmelz et al. 2001)

Debate on DEM reconstruction (Schmelz 2002, Martens et al. 2002, Aschwanden 2002, Schmelz et al. 2003): different results, problem of background subtraction

Schmelz et al. 2001

T

DE

M




Debate on loop DEM

DEM multiplicity (Schmelz et al. 2005):

Analysis of a loop on the limb (CDS/SoHO) Multi-thermal structure at three locations: apex, left and right leg Different from other hot loops looking isothermal (Di Giorgio et al. 2003, Landi &

Landini 2004) CDS atlas reveals many examples of both types of loops: different heating

mechanisms?Di Giorgio et al. 2003

Schmelz et al. 2005




DEM of an active region loop(Di Giorgio et al. 2003)

Analysis of a SoHO/CDS observation of active region loops (14 rasters)




The CDS data




Quantitative analysis:strip enclosing the loop




DEM at the apex sector(raster 4)




Cooler quiescent loop(Reale & Ciaravella 2005, A&A, submitted)

Rationale:

Investigate how far one can go with present loop observations

TRACE-selected loop Multi-wavelength

observation Time-resolved observation Images




The observation

Morphology (TRACE-based selection):

Whole loop visible: OK (171 A filter) Bright: OK Isolated: half On the disk: OK (+230”, +470”) Long-lived (> 2 hours), slowly variable Length: ~1010 cm

Multi-band observation:

TRACE: Filters: 171 A, 195 A, 284 A 32x3 frames (1024x1024, 3.5

hours) Pixel size: 0.5”

SoHO/CDS: Two relevant rasters (i.e. no time

resolution) 11 relevant lines (5.9 < logT

<6.4) Pixel size: 2.5”

Yohkoh/SXT: Nine 512x512 frames (8 AlMg + 1

Al.1) Pixel size: 5”

L




The observation

Time coverage (13 May 1998):

TRACE: 6:30-10:00 UT

Yohkoh/SXT: 6:30-8:40 UT

SoHO/CDS: 7:50-8:46 UT (Raster 1) 10:23-12:12 UT (Raster 2)

L

TRACE

SXT

CDS

6:30UT 12:30UT




The loop life

TRACE Animations:

Time-interpolated images (~3.5 hours) Background subtracted (see below)

The loop is slowly variable:

The brightness distribution changes It fades away




TRACE:Data processing

Pre-processing: trace_prep,wave2p,unspike,destr,derip,new_avg

Alignment: for each filter Cross-correlation (Cross-correlation (align_cube_correlalign_cube_correl))

Background subtraction: Since the loop disappears at the end of the sequence, we

use the last frame (for each filter) as background Subtract the last frame from all others




TRACE: 171 A

Raw images:

Loop: Some

filamentation but globally coherent evolution

best visible after 1 hour

then it fades

Bkg-sub images:

Enhanced loop contrast

Asymmetric evolution:

Right leg first Left leg later

Slow fading




Yohkoh/SXT

Data processing:

Sxt_prep,/register,/vignette Cross-correlation alignment (w/ TRACE

284) Rebinning: pix=1 arcsec Background subtraction: same as TRACE

(AlMg only: no temperature diagnostics)

Raw images:

Similar to TRACE 284 A Loop confused inside an arcade?

Bkg-sub images:

The loop shows up The loop fades Overlaps TRACE loop




TRACE vs Yohkoh

The loops overlap quite well

171 195 284 SXT




Filter ratio maps: 195/171

Temperature indicator Moderate structuring along and across the

loop




The loop analysis

Strip along the loop

Strip divided into sectors




Light curves

e-folding decay time: ~3000 s

Hotter plasma decays sooner

Thermodynamic loop decay time (Serio et al. 1991):

with L94.2 and T70.1

sT

Lth 1600120

7

9




Filter ratio profiles

Del Zanna(http://loopbench.astropa.unipa.it)




Filter ratio

Filter ratio 195/171

Raw

Bkg sub.




Filter ratio evolution

Two regions: Apex (upper points) Whole loop (lower)

The loop cools down




CDS Data Set 14 Rasters 07:13:15 12:11:58 UT 1: FOV too small 3-13: Spectral Range too narrow 2: 07:50:09 - 08:46:02 LOOP 14: 10:23:42 - 12:11:58 Background

Calibration Phot/cm2/sec1/arcsec2/Å Background Subtraction:

no loop in the last raster

SoHO/CDS: the data




BackgroundLoop

Different FOV, Pixels, Spectral linesAligned (align_cube_correl)Rebinned to TRACE Pixels size




Most of the loop is visible in Ca X and Mg IXThe whole loop is visible in Mg X and Si XJust the right end is visible in Si XII, Fe XIV and Fe XVI




CDS lines brightness distributions along the

loop




Emission Measure G(T) function Mazzotta et al. (1998) ionization equilibrium fractions




Results

Hottest: sector 9 Moderate width:

Sharp hot side Smoother cool side

Sector 2: unclear (overlapping structures)




TRACE vs CDS

TRACE 171 A image degraded to CDS space resolution & “rasterized”




DEM of flaring loopsfrom Yohkoh/SXT data

General project: the Sun is our template of X-ray star

For direct comparison with stellar data, we have to translate the solar data into the same passband and format of the stellar data

We need the whole X-ray spectrum of the Sun: not available

Our approach:

Use full-disk space-resolved Yohkoh/SXT data (images in a few wide bands, moderate spectral information)

Derive the EM distribution vs temperature of the whole corona Derive X-ray spectra Derive instrument-filtered X-ray spectra Put spectra at stellar distance




~ simultaneous Yohkoh/SXT

images through different filters

Derive Temperature and emission measure for each pixel

Temperature Emission Measure

From two simultaneous SXT images taken with different filters, derive the temperature and emission measure for each pixel in corona

From the two sets of T and EM values, rearrange and obtain the distribution of emission measure vs. temperature, EM(T): we divide the range of T detectable by the instrument (5.5 < Log T [K] < 8 K) into bins and sum up all the EM values within each “temperature bin”

(Orlando et al., 2000; Peres et al., 2000):

DEM from Yohkoh/SXT data

(Peres, Orlando, Reale, Rosner, Hudson 2000)

Whole-Disk EM(T) Distributions




Flares(Reale, Orlando & Peres 2001)

Selection: from C to X-class




Flare selection: well-observed




Flare DEM evolution from SXT data

Be and thick Al filter bands Flare evolution (time: pale to dark) vs background (quiet/active) corona Result: well-defined peak, small temperature change, larger EM change




If we include more filters….

… the DEM becomes flatter on the cool side

The X-class flare

2-Nov-92, 13:11, AlMg




Overall

Small dependence of T on class X-class: broader and hotter




Synthesis of flare X-ray spectra




THE END




DEM of flaring loops:A different approach

Preface:

The Sun is our star template The Sun is our corona template We resolve the Sun vs we don’t resolve stars

Questions:

Can we use the Sun as a “meter” to “measure” stellar coronae? Can we use the Sun as a guide to study the stellar coronae

Answer:

YES, but we have to translate the solar data into stellar data

Our approach:

Use full-disk space-resolved Yohkoh/SXT data (images in a few wide bands, moderate spectral information)

Derive the EM distribution vs temperature of the whole corona Derive X-ray spectra Derive instrument-filtered X-ray spectra Put spectra at stellar distance

From the EM(T) Distr. to the Coronal Spectrum

6-Jan-92

D = 1 pct_exp = 5 104 sec

… to the X-ray Spectrum of the Sun as a Star

Spectral Synthesis (MEKAL)

Chandra/ACIS

Folding the synthetic spectrum

through the instrument response

Palermo, 14 Sept., 2004

From the EM(T) Distr. to the Coronal Spectrum

Chandra/ACIS

6-Jan-92

D = 1 pct_exp = 2e5 sec

… to the X-ray Spectrum of the Sun as a Star




TRACE: 195 A

Raw images:

More bright structures

Loop visible since the beginning

Bkg-sub images:

Steadily uniform brightness

Gradual fading




TRACE: 284 A

Raw images:

Bright T-like structure

Loop is faint

Bkg-sub images:

Loop faint but visible (right leg)

Faster fading




Yohkoh/SXT

Field of view




Emission profiles

171 A

Raw

Bkg sub

195 A 284 A171 A




Filter ratio

HR 195/171

Raw

Bkg sub.




The hot loop

Let’s focus on the hot loop (Fe XVI): loop A




Multi-wavelength TRACE-selected loop(Reale & Ciaravella 2005, A&A, submitted)

Selection in: list of SoHO campaigns (http://sohodata.nascom.nasa.gov)

Selection made by: F. Reale

SoHO campaign: 5170 Date: 13 May 1998 Name: Active region study Coordinator: Robert Walsh Rationale:

Investigate how deep one can go with present loop observations




TRACE:Data processing

Pre-processing: trace_prep,wave2p,unspike,destr,derip,new_avg

Alignment: for each filter Cross-correlation (Cross-correlation (align_cube_correlalign_cube_correl))

Background subtraction:

Since the loop disappears at the end of the sequence, we use the last frame (for each filter) as background

Subtract the last frame from all others Pros:

In principle, very accurate No interpolation Pixel-by-pixel Analyze all loop pixels

Cons: Assumes no background evolution (13% variations on average) Possible variations of crossing structures

dipartimento di scienze fisiche & astronomiche – universita’ di palermo inaf/osservatorio...

Documents

vaiana fabio reale resik

rhessi spirit workshop

loop slide

isothermal di giorgio

t dem slide

dem reconstruction wide

dem reconstruction schmelz

summary dem of quiescent