PhD Thesis (PDF) - Department of Astronomy - University of Virginia

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source accounts for ∼ 1 4 of the hard counts in the one to three effective radii resolved source region. If we were to exclude this source, the flux ratio between the two regions would be ∼0.65. One would expect that if the unresolved source distribution is the same as the resolved source distribution, we should find a flux ratio between ∼0.6 and 1.0 for the unresolved sources. Instead, the best-fit unresolved emission between one and three effective radii is a purely soft component fit. At best, we can limit the ratio to be 0.15. This suggests that the unresolved source radial distribution may decline more rapidly than the resolved source distribution. Poisson errors in the 2–9 keV count rate of the one to three effective radii unresolved emission are too large to statistically confirm this result. Deeper X-ray observations of NGC 4365 are needed to resolve enough sources to allow the faint source and bright source radial distribution to be compared. NGC 4382 The spectrum of the unresolved emission of the inner two effective radii (Fig- ure 2.10, right-hand panels) had 2620 counts. We initially fitted the spectrum with a model containing only a soft MEKAL component representing emission from diffuse interstellar gas (row 8). The best-fit models with varying absorption gave values be- low the Galactic column, but with an upper limit that included the Galactic value (Table 2.4, row 9). Thus, we chose to use the Galactic column for all remaining fits of this galaxy’s spectra. As with NGC 4365, the addition of a hard component representing unresolved sources led to a much better statistical fit (row 10). Allowing the parameters of the hard component to vary did not result in a significantly better fit, and the hard component parameters were very poorly constrained. Thus, we fixed the shape of the spectrum of the hard component to the adopted model for the 52
esolved sources in the galaxy. This leads to an acceptable fit (row 10); however, its abundance is abnormally high and poorly constrained as a result of minimal emission from hydrogen. Therefore, we have frozen the abundance at 0.5 solar for all remaining soft component fits in this galaxy. This choice (row 11) is very close to the best fit (∆χ 2 = 0.3). This best-fit model has a temperature of 0.28 +0.04 −0.03 and is shown in Figure 2.10. We extracted the unresolved emission spectrum from a larger (but overlapping) elliptical annulus extending from one to three effective radii. The spectrum in this region was reasonably fitted by the same gas temperature and abundance that pro- vided the best fit within two effective radii (row 12). When the gas temperature was allowed to vary (row 13), the best-fit temperature increased; however, that increase was not statistically significant. Unlike in NGC 4365, we find no change in the flux ratio of the resolved and unresolved sources with increasing radius. 2.5.3 Total X-ray Spectra NGC 4365 We first extracted the spectrum of all of the emission within one effective radius. The spectrum in this region is consistent with the best-fit spectra for the resolved and unresolved emission (row 16); when the spectral parameters of the hard and soft components were allowed to vary, the fits were not significantly improved (rows 17 and 18) and did not constrain the abundance. We also attempted a model with a bremsstrahlung hard component (row 19). This fit, slightly better than the power-law model, was more successful at constraining the abundance (5.21 keV). We therefore adopted the sum of the best-fit spectra for the resolved and unresolved emission as our best-fit 53
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LOW-MASS X-RAY BINARIES, DIFFUSE GA
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smaller GCs are more likely to cont
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GO2-3099X, GO3-4099X, AR3-4005X, GO
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her room (my apologies to her offic
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US Court expert from India), for al
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Table of contents Abstract ii Ackno
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5.2.1 Chandra X-ray Observatory . .
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List of Figures 1.1 Hubble Tuning F
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List of Tables 1.1 Galactic Low-Mas
Page 19 and 20: Chapter 1 General Introduction 1.1
Page 21 and 22: Fig. 1.1.— Hubble Tuning Fork, co
Page 23 and 24: 2000). In most HMXBs, the accreted
Page 25 and 26: not get a complete picture of the L
Page 27 and 28: this, the result of dynamical inter
Page 29 and 30: is the Advanced CCD Imaging Spectro
Page 31 and 32: Chapter 2 Chandra Observations of L
Page 33 and 34: keV (Sarazin et al. 2000, 2001). Wi
Page 35 and 36: agreed with positions from the USNO
Page 37 and 38: 24:00 22:00 7:20:00 18:00 16:00 18:
Page 39 and 40: Table 2.1. Discrete X-ray Sources i
Page 41 and 42: Table 2.1—Continued Source d Coun
Page 45 and 46: Table 2.2—Continued Source d Coun
Page 47 and 48: optical/IR positions of R.A. = 12 h
Page 49 and 50: log N(>L) 2.0 1.5 1.0 0.5 0.0 NGC 4
Page 51 and 52: luminosity function for luminositie
Page 53 and 54: H31 1.0 0.5 0.0 -0.5 -1.0 NGC 4365
Page 55 and 56: 2.4.5 Variability We searched for v
Page 57 and 58: Number 10 8 6 4 2 NGC 4365 Optical
Page 59 and 60: LMXBs has an effective radius of 12
Page 61 and 62: component (“MEKAL”) was used fo
Page 63 and 64: Table 2.4. X-ray Spectral Fits of N
Page 65 and 66: Fig. 2.9.— Top panels: Cumulative
Page 67 and 68: we extended the spectrum down to 0.
Page 69: We also examined whether the unreso
Page 73 and 74: temperature ∼0.3 keV. Matsumoto e
Page 75 and 76: log I X (counts/sec/arcmin 2 ) -1.0
Page 77 and 78: ∼45% of the counts are resolved i
Page 79 and 80: Chapter 3 Chandra Observations of D
Page 81 and 82: noninteracting members (de Vaucoule
Page 83 and 84: used for spectroscopic analysis. We
Page 85 and 86: 02:00.0 03:00.0 04:00.0 05:00.0 06:
Page 89 and 90: Table 3.1—Continued d a Count Rat
Page 91 and 92: We also attempted detections in mul
Page 93 and 94: sociated with extended X-ray or opt
Page 95 and 96: Fig. 3.3.— Histogram of the obser
Page 97 and 98: chip. The number of ULX candidates
Page 99 and 100: these luminosities among previously
Page 101 and 102: to 2-6 keV. Since the 6-10 keV rang
Page 103 and 104: absorption and varying power-law in
Page 105 and 106: counts occur within ∼ 4 ks. Sourc
Page 107 and 108: log I X (counts/sec/arcmin 2 ) 0.5
Page 109 and 110: tion), and βouter = 0.36 +0.01 −
Page 111 and 112: the east and northeast of NGC 1600.
Page 113 and 114: group, we assumed that they were at
Page 115 and 116: the group gas than we calculate fro
Page 117 and 118: 04:55 -5:05:00 05 -5:05:10 15 -5:05
Page 119 and 120: for the spectrum: “Field” impli
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90% confidence level errors. Bracke
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we adopted the power-law model as o
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sources could be a non-trivial sour
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jection to include the emission fro
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Fig. 3.13.— Estimated gas and gra
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ackground source population cannot
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NGC 1600 that has a small spatial s
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(HMXBs). LMC X-4, an HMXB pulsar, h
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searched for the shortest time tn o
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with NGC 4697. Columns (1)-(4) list
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duration, ∆tflat, beginning at a
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the uncertainties quoted do not inc
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to persistent rate for short flares
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Chapter 5 Multi-Epoch Chandra X-ray
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the field, these different populati
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luminous (MB < −20) elliptical (E
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Although Chandra is known to encoun
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42:00.0 44:00.0 46:00.0 48:00.0 -5:
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Fig. 5.3.— Adaptively smoothed Ch
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1 × 10 −5 count s −1 arcsec
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Table 5.1—Continued Source R.A. D
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source list against which to regist
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ate from Observation 0784 alone (Pa
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Table 5.2. : Optical Properties of
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actually be an AGN. Sources 79, 80,
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two potential GC counterparts. We l
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Table 5.3—Continued X-ray Source
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Fig. 5.6.— Color (G475−Z850) -
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mass segregation of GCs with the sa
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Table 5.4. Fits to the Expected Num
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dependence are allowed to vary. Var
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NGC 4697 to convert the observed so
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Table 5.6—Continued Source LA LB
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Table 5.6—Continued Source LA LB
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Table 5.7. Combined Luminosities &
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Table 5.7—Continued Source Not De
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Fig. 5.8.— Cumulative luminosity
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LF, there are enough datapoints tha
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Fig. 5.10.— Cumulative luminosity
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Fig. 5.11.— Merged luminosities (
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Fig. 5.12.— X-ray color-color dia
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5.9 Spectral Analysis We performed
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some data loss, it allows for direc
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for 2 dof and the f-test indicates
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ple to LMXBs interior to that semi-
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est-fit (χ 2 = 56.4 for 65 dof) by
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5.10.1 Intraobservation Variability
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Fig. 5.14.— Binned lightcurve usi
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Table 5.10. Possible Flaring Source
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Fig. 5.16.— Cumulative lightcurve
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pairs of observations. In Figure 5.
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Table 5.11—Continued Source PL,AB
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Fig. 5.17.— Percentage of Analysi
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dofs and the number of combinations
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Table 5.12—Continued Source Obs.S
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of states as transient candidates.
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Long-Term Hardness Ratio Variabilit
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In the final observation, there wer
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limits). The 0.3-10 keV X-ray lumin
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atio is expected only from the most
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eak (Kim et al. 2006a). We find mar
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LMXBs in Galactic GCs (Heinke et al
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in the field of the Milky Way and a
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6.2 Sample 6.2.1 Galaxy Sample Tabl
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Table 6.2. Properties of Chandra Ob
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identification of point sources, AC
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the QE degradation in the ACIS dete
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Table 6.3—Continued Galaxy NX LX,
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The positions of the GCs were used
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Fig. 6.2.— Scatter plot of GC gal
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Fig. 6.3.— Scatter plot of estima
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Fig. 6.5.— Scatter plot of estima
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isophote from the galaxy optical su
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6.3.1 Luminosity and Mass Prior obs
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compare their χ 2 fits to test whi
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GCs without LMXBs; however, there a
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following dependence on GC properti
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of this probability with individual
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Fig. 6.9.— Identical to Figure 6.
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We used the indices from our best-f
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(20.3 for half-mass radius, both wi
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most are steeper than Z ∼0.4 . Ei
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Fig. 6.11.— (Left:) Two-dimension
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differently by the properties of th
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dependent IMF (Grindlay 1987), or e
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a 1.4M⊙ neutron star (NS). They s
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equivalent to a dependence on the b
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variability timescale, but it is no
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7.2.1 X-ray Properties of the GC-LM
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of the metallicity dependence. As i
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Appendix A Encounter Rate Parameter
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Fig. A.1.— Dimensionless quantity
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and four; these positions do not in
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Table B.1—Continued RA Dec. d GC
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Table B.2. Optical Properties of Gl
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investigations into improving the h
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C.4 Sivakoff Signature Soy Sauce Sk
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Blanton, E. L., Sarazin, C. L., & I
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Frogel, J. A., Persson, S. E., Matt
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Johnston, H. M. & Verbunt, F. 1996,
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Makishima, K. et al. 2000, ApJ, 535
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Porter, A. C. 1993, PASP, 105, 1250
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Verner, D. A., Ferland, G. J., Kori
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