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X-Ray Populations in the Norma and Scutum -Crux Spiral Arms

X-Ray Populations in the Norma and Scutum -Crux Spiral Arms. Francesca Fornasini, UC Berkeley In collaboration with: J. A. Tomsick , F. Rahoui , A. Bodaghee , R. A. Krivonos , H. An, E. V. Gotthelf , V. M. Kaspi , F. E. Bauer, D. Stern, S. E. Boggs .

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X-Ray Populations in the Norma and Scutum -Crux Spiral Arms

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  1. X-Ray Populations in the Norma and Scutum-Crux Spiral Arms Francesca Fornasini, UC Berkeley In collaboration with: J. A. Tomsick, F. Rahoui, A. Bodaghee, R. A. Krivonos, H. An, E. V. Gotthelf, V. M. Kaspi, F. E. Bauer, D. Stern, S. E. Boggs

  2. Chandra Observations of the Norma Region • Search for new HMXBs and study hard X-ray populations • Twenty-seven 20 kspointings • Red: 0.5-2 keVGreen: 2-4.5 keVBlue: 4.5-10 keV Bodaghee et al. 2012 HMXB Young Massive Clusters -0.4° b 0.4° Supernova Remnants Magnetar PWN 338° l 337° HEAD 13th Meeting, 2013

  3. Now I wonder what you are • Two main analyses to help classify X-ray sources: • Dividing sources into spectral groups • Making stacked spectra, analyzing variability and counterparts of sources in each group • Near-IR follow-up of individual sources • 30 J, H, K spectra obtained using OSIRIS on the SOAR telescope • Selected sources based on X-ray brightness, spectral hardness, variability, and IR counterpart reliability and magnitude HEAD 13th Meeting, 2013

  4. Now I wonder what you are • Two main analyses to help classify X-ray sources: • Dividing sources into spectral groups • Making stacked spectra, analyzing variability and counterparts of sources in each group • Near-IR follow-up of individual sources • 30 J, H, K spectra obtained using OSIRIS on the SOAR telescope • Selected sources based on X-ray brightness, spectral hardness, variability, and IR counterpart reliability and magnitude HEAD 13th Meeting, 2013

  5. Defining Spectral Groups >3σ sources (0.5-10 keV) Broadness Hardness HEAD 13th Meeting, 2013 Quantile grid method developed by Hong et al. 2004

  6. Defining Spectral Groups Broadness Hardness HEAD 13th Meeting, 2013

  7. Defining Spectral Groups Soft, high absorption Hard, high absorption Soft, low absorption Broadness Hard, moderate absorption Hard, low absorption Hardness HEAD 13th Meeting, 2013

  8. Group D • Probably dominated by intermediate polars in the far Norma arm. HMXBs are most likely to be in this group. • Power-law: • Γ = 0.7±0.1 • NH = 6.8±0.6 x 1022 cm-2 • Fe line: • Line = 6.62±0.03 keV • Eq width = 360±70 eV HEAD 13th Meeting, 2013

  9. Dominant X-Ray Populations Colliding wind binaries, high-mass stars IPs, HMXBs X-ray active stars, RS CVn Broadness CVs, RS CVn CVs Hardness HEAD 13th Meeting, 2013

  10. LogN-logS Corrected for differences in sensitivity across surveyed area and Eddington bias as discussed in Georgakakis et al. 2008 >3σ sources (2-10 keV) Broadness Hardness HEAD 13th Meeting, 2013

  11. Now I wonder what you are • Two main analyses to help classify X-ray sources: • Dividing sources into spectral groups • Making stacked spectra, analyzing variability and counterparts of sources in each group • Near-IR follow-up of individual sources • 30 J, H, K spectra obtained using OSIRIS on the SOAR telescope • Selected sources based on X-ray brightness, spectral hardness, variability, and IR counterpart reliability and magnitude HEAD 13th Meeting, 2013

  12. Low-mass counterparts • 13 show CO lines typical of low-mass stars and cool giants • consistent with a dominant CV population • 1 shows accretion disk signatures > magnetic CV • Γ = 1.1 ± 0.1, NH = 1.2 ± 0.1 x 1021 cm-2 , P ≈ 3500 sec, L2-10~ 1032 erg/s K band K band Near-IR diagnostics: Wallace & Hinkle 1996, Meier et al. 1998, Förster Schreiber 2000, Ivanov et al. 2004, Rayner et al. 2009 HEAD 13th Meeting, 2013

  13. High-mass counterparts • 6 spectra show lines typical of O, B, Be, or WR stars • 2 are possible HMXBs in the far Norma arm • 2 are likely massive stars in the far Norma arm • 2 are sources in the Scutum-Crux or near Norma arm Broadness H band K band Hardness HEAD 13th Meeting, 2013 Near-IR diagnostics: Hanson & Conti 1996, Morris et al. 1996, Hanson et al. 1998, Meier et al. 1998, Hanson et al. 2005

  14. Summary and Outlook • Magnetic CVs are the dominant X-ray population in the Norma spiral arm, many of which appear to be intermediate polars. • The potential HMXBs we have discovered are faint and could be useful in constraining the faint end of the HMXB luminosity function. • Ongoing IR follow-up and a NuSTAR survey of this region will help to uncover other potential HMXBs and to constrain their hard X-ray spectral properties. HEAD 13th Meeting, 2013

  15. Other clues for classifying sources • IR counterparts from VISTA VVV survey • Low-mass, foreground stars • Cool giants and high mass stars, near arm • Cool giants and high mass stars, far arm HEAD 13th Meeting, 2013

  16. Other clues for classifying sources • Short-timescale variability • 21 of 28 variable sources (95% confidence) belong to groups A and B > consistent with foreground flaring stars • Long-timescale variability • RS CVn systems can flare by factor of 10 in amplitude • HMXBs and X-rays from high-mass winds are variable • Intermediate polars have fairly constant emission HEAD 13th Meeting, 2013

  17. Group A • Dominated by low-mass X-ray active stars, RS CVn systems in the foreground. • Red dashed: • kT = 2.1+0.3-0.1keV • NH = 5+5-4x 1020 cm-2 • Blue dotted: • kT = 0.76±0.04 keV • NH = 3±1 x 1021 cm-2 HEAD 13th Meeting, 2013

  18. Group B • Mixture of foreground active stars and magnetic CVs in the Scutum/near Norma arms. • Red dashed component: • kT = 5.9 keV • NH = 3.0 x 1021 cm-2 • Blue dotted component: • kT = 1.0 keV • NH < 4 x 1020 cm-2 HEAD 13th Meeting, 2013

  19. Group C • Dominated by magnetic CVs in the Scutum/near Norma arms. • Red dashed component: • Γ = 1.2 • NH = 1.5 x 1022 cm-2 • Blue dotted component: • Line = 6.8 keV • Eq width = 400 eV HEAD 13th Meeting, 2013

  20. Group E • Mixture of isolated high-mass stars, colliding wind binaries, symbiotic binaries in the far Norma arm. Possible contamination from group D IPs. • Red dashed component: • kT = 1.8 keV • NH = 2.3 x 1023 cm-2 • Blue dotted component: • kT = 1.45 keV • NH = 4.1 x 1022 cm-2 HEAD 13th Meeting, 2013

  21. AGN Contribution HEAD 13th Meeting, 2013

  22. LogN-logS for all groups HEAD 13th Meeting, 2013

  23. LogN-logS Sensitivity curve method developed by Georgakakis et al. 2008 >3σ sources (2-10 keV) Broadness Hardness HEAD 13th Meeting, 2013

  24. HMXB Luminosity Function • Blue: if all 4 potential HMXBs are HMXBs 17-60 keV - - - Chandra: Grimm et al. 2002 – – Swift BAT: Voss & Ajello 2010 ––– INTEGRAL: Lutovinov et al. 2013 HEAD 13th Meeting, 2013

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