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 ID: 196655
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Slide1
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 Slide2
Chandra Observations of the Norma Region
Bodaghee
et al. 2012
Search for new
HMXBs
and study hard X-ray populationsTwenty-seven 20 ks pointingsRed: 0.5-2 keV Green: 2-4.5 keV Blue: 4.5-10 keV
HEAD 13th Meeting, 2013
338°
l
337°
-0.4° b 0.4°
HMXB
Magnetar
PWN
Supernova Remnants
Young Massive ClustersSlide3
Now I wonder what you areTwo 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, 2013Slide4
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, 2013Slide5
Defining Spectral Groups
Quantile
grid method developed by Hong et al. 2004
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Broadness
Hardness
>3σ sources (0.5-10 keV)Slide6
Defining Spectral Groups
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Broadness
HardnessSlide7
Defining Spectral Groups
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Hardness
Broadness
Soft, low absorption
Soft, high absorption
Hard, high absorptionHard, moderate absorption
Hard, low absorption Slide8
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±0.1NH = 6.8±0.6 x 1022 cm-2Fe line
:Line = 6.62±0.03 keVEq width = 360±70 eVHEAD 13th Meeting, 2013Slide9
Dominant X-Ray Populations
HEAD 13th Meeting, 2013
Hardness
Broadness
X-ray active stars, RS
CVn
CVs, RS CVnCVs
IPs,
HMXBs
Colliding wind binaries, high-mass starsSlide10
>3σ sources (2-10
keV
)
Broadness
Hardness
LogN-logS
HEAD 13th Meeting, 2013Corrected for differences in sensitivity across surveyed area and Eddington bias as discussed in Georgakakis et al. 2008Slide11
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 magnitudeHEAD 13th Meeting, 2013Slide12
Low-mass counterparts13 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/sHEAD 13th Meeting, 2013K band
K bandNear-IR diagnostics: Wallace & Hinkle 1996, Meier et al. 1998, Förster Schreiber 2000, Ivanov
et al. 2004, Rayner et al. 2009Slide13
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
HEAD 13th Meeting, 2013
K band
H band
Hardness
Broadness
Near-IR diagnostics: Hanson & Conti 1996, Morris et al. 1996, Hanson et al. 1998, Meier et al. 1998, Hanson et al. 2005Slide14
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, 2013Slide15
IR counterparts from VISTA VVV surveyLow-mass, foreground starsCool giants and high mass stars, near arm
Cool giants and high mass stars, far arm
Other clues for classifying sources
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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 amplitudeHMXBs and X-rays from high-mass winds are variableIntermediate polars have fairly constant emission
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Group A
Dominated by low-mass X-ray active stars, RS
CVn
systems in the foreground.
Red dashed:
kT = 2.1+0.3-0.1 keVNH = 5+5-4 x 1020 cm-2
Blue dotted:kT = 0.76±0.04 keVNH = 3±1 x 10
21 cm-2
HEAD 13th Meeting, 2013Slide18
Group B
Mixture of foreground active stars and magnetic CVs in the
Scutum
/near Norma arms.
Red dashed component:
kT = 5.9 keVNH = 3.0 x 1021 cm-2Blue dotted
component:kT = 1.0 keVNH < 4 x 1020 cm-2
HEAD 13th Meeting, 2013Slide19
Group C
Dominated by magnetic CVs in the
Scutum
/near Norma arms.
Red dashed component:
Γ = 1.2NH = 1.5 x 1022 cm-2Blue dotted component:
Line = 6.8 keVEq width = 400 eVHEAD 13th Meeting, 2013Slide20
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 keVNH = 2.3 x 1023 cm-2Blue dotted
component:kT = 1.45 keVNH = 4.1 x 1022 cm-2
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AGN Contribution
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LogN-logS for all groups
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>3σ sources (2-10
keV
)
Broadness
Hardness
LogN-logS
HEAD 13th Meeting, 2013Sensitivity curve method developed by Georgakakis et al. 2008Slide24
HMXB Luminosity Function
Blue: if all 4 potential
HMXBs
are
HMXBs
HEAD 13th Meeting, 201317-60 keV––– INTEGRAL: Lutovinov et al. 2013
– – Swift BAT: Voss & Ajello 2010- - - Chandra: Grimm et al. 2002