Chandra Observations of the Norma Region Bodaghee et al. 2012
Search for new HMXBs and study hard X-ray populations Twenty-seven
20 ks pointings Red: 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 Clusters
Slide 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
Slide 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
Slide 5
Defining Spectral Groups Quantile grid method developed by Hong
et al. 2004 HEAD 13th Meeting, 2013 Broadness Hardness >3
sources (0.5-10 keV)
Slide 6
Defining Spectral Groups HEAD 13th Meeting, 2013 Broadness
Hardness
Slide 7
Defining Spectral Groups HEAD 13th Meeting, 2013 Hardness
Broadness Soft, low absorption Soft, high absorption Hard, high
absorption Hard, moderate absorption Hard, low absorption
Slide 8
Group D Probably dominated by intermediate polars in the far
Norma arm. HMXBs are most likely to be in this group. Power-law: =
0.70.1 N H = 6.80.6 x 10 22 cm -2 Fe line: Line = 6.620.03 keV Eq
width = 36070 eV HEAD 13th Meeting, 2013
>3 sources (2-10 keV) Broadness Hardness LogN-logS HEAD 13th
Meeting, 2013 Corrected for differences in sensitivity across
surveyed area and Eddington bias as discussed in Georgakakis et al.
2008
Slide 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
Slide 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 = 1.1 0.1, N H =
1.2 0.1 x 10 21 cm -2, P 3500 sec, L 2-10 ~ 10 32 erg/s HEAD 13th
Meeting, 2013 K band Near-IR diagnostics: Wallace & Hinkle
1996, Meier et al. 1998, Frster Schreiber 2000, Ivanov et al. 2004,
Rayner et al. 2009
Slide 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 HEAD 13th Meeting, 2013 K bandH band
Hardness Broadness Near-IR diagnostics: Hanson & Conti 1996,
Morris et al. 1996, Hanson et al. 1998, Meier et al. 1998, Hanson
et al. 2005
Slide 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
Slide 15
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
Slide 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
Slide 17
Group A Dominated by low-mass X-ray active stars, RS CVn
systems in the foreground. Red dashed: kT = 2.1 +0.3 -0.1 keV N H =
5 +5 -4 x 10 20 cm -2 Blue dotted: kT = 0.760.04 keV N H = 31 x 10
21 cm -2 HEAD 13th Meeting, 2013
Slide 18
Group B Mixture of foreground active stars and magnetic CVs in
the Scutum/near Norma arms. Red dashed component: kT = 5.9 keV N H
= 3.0 x 10 21 cm -2 Blue dotted component: kT = 1.0 keV N H < 4
x 10 20 cm -2 HEAD 13th Meeting, 2013
Slide 19
Group C Dominated by magnetic CVs in the Scutum/near Norma
arms. Red dashed component: = 1.2 N H = 1.5 x 10 22 cm -2 Blue
dotted component: Line = 6.8 keV Eq width = 400 eV HEAD 13th
Meeting, 2013
Slide 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
N H = 2.3 x 10 23 cm -2 Blue dotted component: kT = 1.45 keV N H =
4.1 x 10 22 cm -2 HEAD 13th Meeting, 2013
Slide 21
AGN Contribution HEAD 13th Meeting, 2013
Slide 22
LogN-logS for all groups HEAD 13th Meeting, 2013
Slide 23
>3 sources (2-10 keV) Broadness Hardness LogN-logS HEAD 13th
Meeting, 2013 Sensitivity curve method developed by Georgakakis et
al. 2008
Slide 24
HMXB Luminosity Function Blue: if all 4 potential HMXBs are
HMXBs HEAD 13th Meeting, 2013 17-60 keV INTEGRAL: Lutovinov et al.
2013 Swift BAT: Voss & Ajello 2010 - - - Chandra: Grimm et al.
2002
