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
HEAD 13th Meeting, 2013
Chandra Observations of the Norma Region
Bodaghee et al. 2012
Search for new HMXBs and study hard X-ray populations
Twenty-seven 20 ks pointingsRed: 0.5-2 keV Green: 2-4.5 keV Blue: 4.5-10 keV
338° l 337°
-0.4
°
b
0
.4°
HMXB
MagnetarPWNSupernova Remnants
Young Massive Clusters
HEAD 13th Meeting, 2013
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 sources30 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
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 sources30 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
Defining Spectral Groups
Quantile grid method developed by Hong et al. 2004
Broa
dnes
s
Hardness
>3σ sources (0.5-10 keV)
HEAD 13th Meeting, 2013
Defining Spectral GroupsBr
oadn
ess
Hardness
HEAD 13th Meeting, 2013
Defining Spectral Groups
Hardness
Broa
dne
ss
Soft, low absorption
Soft, high absorption Hard,
high absorption
Hard, moderate absorption
Hard, low absorption
HEAD 13th Meeting, 2013
Group DProbably 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-2
Fe line:Line = 6.62±0.03
keVEq width = 360±70
eV
HEAD 13th Meeting, 2013
Dominant X-Ray Populations
Hardness
Broa
dne
ss
X-ray active stars, RS CVn
CVs, RS CVn
CVs
IPs, HMXBs
Colliding wind binaries, high-mass stars
HEAD 13th Meeting, 2013
>3σ sources (2-10 keV)
Broa
dne
ss
Hardness
LogN-logSCorrected for differences in sensitivity across surveyed area and Eddington bias as discussed in Georgakakis et al. 2008
HEAD 13th Meeting, 2013
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 sources30 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
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/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
High-mass counterparts6 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
K bandH band
Hardness
Broa
dnes
s
Near-IR diagnostics: Hanson & Conti 1996, Morris et al. 1996, Hanson et al. 1998, Meier et al. 1998, Hanson et al. 2005
HEAD 13th Meeting, 2013
Summary and OutlookMagnetic 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
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
Other clues for classifying sources
HEAD 13th Meeting, 2013
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
Group ADominated 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 1021
cm-2
HEAD 13th Meeting, 2013
Group BMixture 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-2
Blue dotted component:kT = 1.0 keVNH < 4 x 1020 cm-
2
HEAD 13th Meeting, 2013
Group CDominated by magnetic CVs
in the Scutum/near Norma arms.
Red dashed component:Γ = 1.2NH = 1.5 x 1022
cm-2
Blue dotted component:Line = 6.8 keVEq width = 400
eV
HEAD 13th Meeting, 2013
Group EMixture 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-2
Blue dotted component:kT = 1.45 keVNH = 4.1 x 1022
cm-2
HEAD 13th Meeting, 2013
AGN Contribution
HEAD 13th Meeting, 2013
LogN-logS for all groups
HEAD 13th Meeting, 2013
>3σ sources (2-10 keV)
Broa
dne
ss
Hardness
LogN-logSSensitivity curve method developed by Georgakakis et al. 2008
HEAD 13th Meeting, 2013
HMXB Luminosity Function
Blue: if all 4 potential HMXBs are HMXBs
17-60 keV
––– INTEGRAL: Lutovinov et al. 2013
– – Swift BAT: Voss & Ajello 2010
- - - Chandra: Grimm et al. 2002
