Spectrum Analysis Spectrum Analysis ofof

SGR 1900+14 in SGR 1900+14 in quiescentquiescent

Spectrum Analysis Spectrum Analysis ofof

SGR 1900+14 in SGR 1900+14 in quiescentquiescent

(2nd edition)(2nd edition)

Bubu 2002/12/12&18

Contents• About SGR 1900+14• My job• Show time!!• Current results• Conclusion (and next step)

About SGR1900+14• One of the 4+1 SGRs• In the galactic plane• Spin-down energy problem• More correct position: “19 07 14.1, 09 19 01”• Models for it in quiescent: No really serious one!! • History: discover:1979 giant flare: 1998/8/27

Similar to AXPs

My job• At present, most papers fit the spectrum of

SGRs in quiescence with a “power law” • From the data of AXPs, we may use two or

more blackbody plus a power law to fit its spectrum.

• This gives us a hint that maybe we can fit the spectrum of SGRs in the same way.

• The result, will provide some constraints and hints about what SGRs and AXPs are.

These help a more correct and detailed physical explanation.

Flow chart of my job:

ftp.asdc.asi

/anonymous

In spec analysis,we need……

• *.pha• *.rmf (response matrix file)• *.arf (ancillary response file)• Background files (Make it by yourself!)

“Channel type”• PHA The device which measures the energy of

a photon, often used to the refer to the raw numbers measured by the device.

• PI Pulse invariant. PHA values corrected for

spatial and temporal changes in gain.

Next,

Before show time………

Header of MECS2_70249001.evt• Naxis2=10926 /number of rows in

table• CONTENT=‘EVENT LIST’• TELESCOP=‘SAX’• INSTRUME=‘MECS2’• OBJECT=‘SGR 1900+14’• RA_OBJ= 286.8125 • DEC_OBJ=9.3225• DATE-OBS=‘1997-05-12’• TIME-OBS=’01:21:50.000’ /(HH:MM:SS)• DATA-END=‘1997-05-13’• TIME-END=’01:05:26.0000’

And………

Some points……:

• SAOimage: How to determine the center and the radius of the

region?• Xselect: How to filter time and region (and pha_cutoff), the

n extract spectrum? • Xspec: What models should we consider? How to choose a

model? How we say a fitting is good or not? • BeppoSAX MECS2: What steps will it influence?

Go!

!

In Xspec analysis,we need……

• *.pha• *.rmf (response matrix file)• *.arf (ancillary response file)• Background files (Make it by yourself!!)

One way to make a background file (blank

field) :

2.8279E-03 counts/sec

5.2428E-03 counts/sec

4.7622E-03 counts/sec

• Note: in DETX DETY coordinate

• (5.2428+4.7622)/2.8279=5

corfile

cornorm

Current results:data "bubu.pha"Backgrnd & corfile “bubu_bgd.pha"response "mecs2_sep

97.rmf "arf "mecs2_4_sep97.a

rf "ignore 1-37 227-**

In Xspec, there are two basic kinds of model components:• Additive model components (sources)

• Multiplicative model components

• (mixing, convolution, pile up)• There must be least one additive

component in a model

About bbody (Additive)

• A blackbody spectrum.------------------------------------------------------------------- A(E) = K 8.0525 E**2 dE / ((par1)**4 (exp(E/par1)-1))-------------------------------------------------------------------

where :

par1 = temperature kT in keV

K = L39/(D10)**2, where L39 is the source luminosity in units of 10**39 ergs/sec and D10 is the distance to the source in units of 10 kpc

About bremss (Additive)• A thermal bremsstrahlung spectrum based on the Kellogg, B

aldwin & Koch(ApJ 199, 299) polynomial fits to the Karzas & Latter numerical values.

• A routine from Kurucz is used for low temperatures. The He abundance is assumed to be 8.5% by number.

par1 = plasma temperature in keV

K = (3.02e-15/4/pi/D^2) Int n_e n_I dV

where n_e is the electron density (cm^-3), n_I is the iondensity (cm^-3), and D is the distance to the source (cm).

About powerlaw (Additive)

• Simple photon power law.-------------------------------------------------------- A(E) = K (E/1 keV)**(-par1)--------------------------------------------------------where :

par1 = photon index of power law (dimensionless) K = photons/keV/cm**2/s at 1 keV.

About phabs (multiplicative)

• Photoelectric absorption using cross-sections set by the xsect command.The relative abundances are set by the abund command.------------------------------------------------------------------- A(E) = exp(-par1*sigma(E))-------------------------------------------------------------------where sigma(E) is the photo-electric cross-section (NOT including Thomson scattering). Note that the default He cross-section changed in v11. The old version can be recovered using the command xsect obcm.

par1 = equivalent hydrogen column (in units of 10**22 atoms/cm**2)

I’ll fit models for:• 1_Phab(po)• 2_phab(bb)• 3_phab(bb+po)• 4_phab(bb+bb)• 5_phab(br)• 6_phab(bb+br)• 7_phab(br+po)• 8_phab(bb+br+po)

1_Model: phabs[1]( powerlaw[2] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 1.067 +/- 0.3301 2 2 2 powerlaw PhoIndex 1.987 +/- 0.1283 3 3 2 powerlaw norm 2.9807E-03 +/- 0.9752E-03 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 186.4382 using 190 PHA bins.

Reduced chi-squared = 0.9969957 for 187 degrees of freedom

Null hypothesis probability = 0.498

1_Model: phabs[1]( powerlaw[2] )

2_Model: phabs[1]( bbody[2] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 0.000 +/- -1.000 2 2 2 bbody kT keV 1.110 +/- 0.2619E-01 3 3 2 bbody norm 8.6667E-05 +/- 0.4542E-05 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 274.2688 using 190 PHA bins.

Reduced chi-squared = 1.466678 for 187 degrees of freedom Null hypothesis probability = 3.317E-05

2_Model: phabs[1]( bbody[2] )

3_Model: phabs[1]( bbody[2] + powerlaw[3] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 2.949 +/- 1.147 2 2 2 bbody kT keV 3.032 +/- 1.579 3 3 2 bbody norm 7.9305E-05 +/- 0.6007E-04 4 4 3 powerlaw PhoIndex 3.364 +/- 0.9279 5 5 3 powerlaw norm 1.7330E-02 +/- 0.1784E-01 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 180.8243 using 190 PHA bins.

Reduced chi-squared = 0.9774286 for 185 degrees of freedom Null hypothesis probability = 0.573

3_Model: phabs[1]( bbody[2] + powerlaw[3] )

4_Model: phabs[1]( bbody[2] + bbody[3] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 1.092 +/- 0.7154 2 2 2 bbody kT keV 2.318 +/- 0.3807 3 3 2 bbody norm 9.1681E-05 +/- 0.2009E-04 4 4 3 bbody kT keV 0.6055 +/- 0.8454E-01 5 5 3 bbody norm 7.2289E-05 +/- 0.3571E-04 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 176.3595 using 190 PHA bins.

Reduced chi-squared = 0.9532943 for 185 degrees of freedom Null hypothesis probability = 0.663

4_Model: phabs[1]( bbody[2] + bbody[3] )

5_Model: phabs[1]( bremss[2] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 0.4176 +/- 0.2399 2 2 2 bremss kT keV 9.208 +/- 1.773 3 3 2 bremss norm 2.1056E-03 +/- 0.2931E-03 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 190.5356 using 190 PHA bins.

Reduced chi-squared = 1.018907 for 187 degrees of freedom Null hypothesis probability = 0.414

5_Model: phabs[1]( bremss[2] )

6_Model: phabs[1]( bbody[2] + bremss[3] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 2.481 +/- 0.7823 2 2 2 bbody kT keV 2.482 +/- 0.5976 3 3 2 bbody norm 9.1600E-05 +/- 0.2621E-04 4 4 3 bremss kT keV 1.393 +/- 0.4551 5 5 3 bremss norm 1.1180E-02 +/- 0.8392E-02 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 178.9737 using 190 PHA bins.

Reduced chi-squared = 0.9674256 for 185 degrees of freedom Null hypothesis probability = 0.611

6_Model: phabs[1]( bbody[2] + bremss[3] )

•

7_Model: phabs[1]( bremss[2] + powerlaw[3] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 2.270 +/- 1.003 2 2 2 bremss kT keV 1.255 +/- 0.7542 3 3 2 bremss norm 9.4088E-03 +/- 0.1118E-01 4 4 3 powerlaw PhoIndex 1.255 +/- 0.7725 5 5 3 powerlaw norm 7.0125E-04 +/- 0.2141E-02 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 180.7877 using 190 PHA bins.

Reduced chi-squared = 0.9772307 for 185 degrees of freedom Null hypothesis probability = 0.574

7_Model: phabs[1]( bremss[2] + powerlaw[3] )

8_Model: phabs[1]( bbody[2] + powerlaw[3] + bremss[4] )

Model Fit Model Component Parameter Unit Value par par comp 1 1 1 phabs nH 10^22 3.379 +/- 6.896 2 2 2 bbody kT keV 2.985 +/- 2.273 3 3 2 bbody norm 7.0254E-05 +/- 0.7403E-04 4 4 3 powerlaw PhoIndex 3.494 +/- 3.013 5 5 3 powerlaw norm 2.2387E-02 +/- 0.9565E-01 6 6 4 bremss kT keV 0.1548 +/- 0.1014 7 7 4 bremss norm 43.67 +/- 0.1629E+05 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 181.1675 using 190 PHA bins.

Reduced chi-squared = 0.9899863 for 183 degrees of freedom Null hypothesis probability = 0.524

8_Model: phabs[1]( bbody[2] + powerlaw[3] +

bremss[4] )

Null hypothesis probability of these models are:

• 1_Phab(po)

• 2_phab(bb)• 3_phab(bb+po)• 4_phab(bb+bb)• 5_phab(br)• 6_phab(bb+br)• 7_phab(br+po)• 8_phab(bb+br+po

)

• 0.498• 3.317E-05• 0.573• 0.663• 0.414• 0.611• 0.574• 0.524

But……Astro-ph/9912061

Conclusion (& next step):

• error, recornrm• α=2.2??• Reasonable!!• Try MECS and LECS data.• Compare with more results.• Uncertainties??......

It’s a long road……”\|O.oIt’s a long road……”\|O.o|/”|/”

It’s a long road……”\|O.oIt’s a long road……”\|O.o|/”|/”