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Spectrum Analysis of SGR 1900+14 in quiescent (2nd edition) Bubu 2002/12/12&18.

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Presentation on theme: "Spectrum Analysis of SGR 1900+14 in quiescent (2nd edition) Bubu 2002/12/12&18."— Presentation transcript:

1 Spectrum Analysis of SGR in quiescent (2nd edition) Bubu 2002/12/12&18

2 Contents About SGR My job Show time!! Current results Conclusion (and next step)

3 About SGR One of the 4+1 SGRs In the galactic plane Spin-down energy problem More correct position: “ , ” Models for it in quiescent: No really serious one!! History: discover:1979 giant flare: 1998/8/27 Similar to AXPs

4 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.

5 Flow chart of my job: ftp.asdc.asi /anonymous

6 In spec analysis, we need …… *.pha *.rmf (response matrix file) *.arf (ancillary response file) Background files (Make it by yourself!)

7 “ 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.

8 Next, Before show time ………

9 Header of MECS2_ evt Naxis2=10926 /number of rows in table CONTENT= ‘ EVENT LIST ’ TELESCOP= ‘ SAX ’ INSTRUME= ‘ MECS2 ’ OBJECT= ‘ SGR ’ RA_OBJ= DEC_OBJ= DATE-OBS= ‘ ’ TIME-OBS= ’ 01:21: ’ /(HH:MM:SS) DATA-END= ‘ ’ TIME-END= ’ 01:05: ’ And ………

10 Some points …… : SAOimage: How to determine the center and the radius of the region? Xselect: How to filter time and region (and pha_cutoff), then 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!!

11 In Xspec analysis, we need …… *.pha *.rmf (response matrix file) *.arf (ancillary response file) Background files (Make it by yourself!!)

12 One way to make a background file (blank field) : E-03 counts/sec E-03 counts/sec E-03 counts/sec Note: in DETX DETY coordinate ( )/2.8279=5 corfile cornorm

13 Current results: data "bubu.pha" Backgrnd & corfile “ bubu_bgd.pha" response "mecs2_sep97.rmf " arf "mecs2_4_sep97.arf " ignore **

14 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

15 About bbody (Additive) A blackbody spectrum A(E) = K 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

16 About bremss (Additive) A thermal bremsstrahlung spectrum based on the Kellogg, Baldwin & 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 ion density (cm^-3), and D is the distance to the source (cm).

17 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.

18 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)

19 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)

20 1_Model: phabs[1]( powerlaw[2] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / powerlaw PhoIndex / powerlaw norm E-03 +/ E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 187 degrees of freedom Null hypothesis probability = 0.498

21 1_Model: phabs[1]( powerlaw[2] )

22 2_Model: phabs[1]( bbody[2] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / bbody kT keV / E bbody norm E-05 +/ E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 187 degrees of freedom Null hypothesis probability = 3.317E-05

23 2_Model: phabs[1]( bbody[2] )

24 3_Model: phabs[1]( bbody[2] + powerlaw[3] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / bbody kT keV / bbody norm E-05 +/ E powerlaw PhoIndex / powerlaw norm E-02 +/ E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 185 degrees of freedom Null hypothesis probability = 0.573

25 3_Model: phabs[1]( bbody[2] + powerlaw[3] )

26 4_Model: phabs[1]( bbody[2] + bbody[3] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / bbody kT keV / bbody norm E-05 +/ E bbody kT keV / E bbody norm E-05 +/ E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 185 degrees of freedom Null hypothesis probability = 0.663

27 4_Model: phabs[1]( bbody[2] + bbody[3] )

28 5_Model: phabs[1]( bremss[2] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / bremss kT keV / bremss norm E-03 +/ E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 187 degrees of freedom Null hypothesis probability = 0.414

29 5_Model: phabs[1]( bremss[2] )

30 6_Model: phabs[1]( bbody[2] + bremss[3] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / bbody kT keV / bbody norm E-05 +/ E bremss kT keV / bremss norm E-02 +/ E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 185 degrees of freedom Null hypothesis probability = 0.611

31 6_Model: phabs[1]( bbody[2] + bremss[3] )

32 7_Model: phabs[1]( bremss[2] + powerlaw[3] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / bremss kT keV / bremss norm E-03 +/ E powerlaw PhoIndex / powerlaw norm E-04 +/ E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 185 degrees of freedom Null hypothesis probability = 0.574

33 7_Model: phabs[1]( bremss[2] + powerlaw[3] )

34 8_Model: phabs[1]( bbody[2] + powerlaw[3] + bremss[4] ) Model Fit Model Component Parameter Unit Value par par comp phabs nH 10^ / bbody kT keV / bbody norm E-05 +/ E powerlaw PhoIndex / powerlaw norm E-02 +/ E bremss kT keV / bremss norm / E Chi-Squared = using 190 PHA bins. Reduced chi-squared = for 183 degrees of freedom Null hypothesis probability = 0.524

35 8_Model: phabs[1]( bbody[2] + powerlaw[3] + bremss[4] )

36 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) E

37 But …… Astro-ph/

38 Conclusion (& next step): error, recornrm α=2.2?? Reasonable!! Try MECS and LECS data. Compare with more results. Uncertainties??......

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


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