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Spectrum Analysis of SGR 1900+14 in quiescent

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

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Spectrum Analysis of SGR 1900+14 in quiescent

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

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

  3. 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

  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_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………

  10. Some points……: Go!! • 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?

  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): Note: in DETX DETY coordinate 2.8279E-03 counts/sec corfile 4.7622E-03 counts/sec cornorm 5.2428E-03 counts/sec (5.2428+4.7622)/2.8279=5

  13. Current results: data "bubu.pha" Backgrnd & corfile “bubu_bgd.pha" response "mecs2_sep97.rmf " arf "mecs2_4_sep97.arf " ignore 1-37 227-**

  14. In Xspec, there are two basic kinds of model components: • Additivemodel 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 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

  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 iondensity (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 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

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

  22. 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

  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 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

  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 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

  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 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

  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 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

  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 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

  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 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

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

  36. Null hypothesis probability of these models are: 0.498 3.317E-05 0.573 0.663 0.414 0.611 0.574 0.524 • 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)

  37. But…… Astro-ph/9912061

  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|/”

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