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

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Table 4.1. Observed Properties of Short-Timescale Flares in NGC 4697 ∆t t0 Pconstant P ′ constant Pconstant,joint Source Name R.A. Decl. Obs. N n (s) (MJD) (%) (%) (%) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) CXOU J124837.8−054652 (source A) ..... 12 48 37.86 −05 46 52.9 0784 14 5 1047 51558.79424 0.700 1.787 4727 16 4 628 52999.75883 2.729 7.006 4728 14 4 509 53010.70296 1.212 3.096 0784,4727,4728 0.039 CXOU J124831.0−054828 (source B) ..... 12 48 31.04 −05 48 28.8 4727 9 5 1329 53000.04327 0.224 0.552 4728 9 4 1420 53010.72445 3.368 7.982 4729 6 5 5654 53047.59917 4.327 9.007 4727,4728 0.441 4727–4729 0.040 CXOU J124839.0−054750 (source C) ..... 12 48 39.03 −05 47 50.2 0784 20 4 68 51558.95771 0.013 0.034 4727 20 3 50 53000.05857 0.547 1.420 0784,4727 0.005 NOTE.—Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcseconds. Table 4.2. Inferred Properties of Short-Timescale Flares in NGC 4697 rflat ∆tflat Lflare Eflare Source Name Obs. nflat (10−3 s−1 ) (s) rflat/rpersistent (1038 ergs s−1 ) (1041 ergs) (1) (2) (3) (4) (5) (6) (7) (8) CXOU J124837.8−054652 (source A) .... 0784 3.7 +4.1 + 17.4 −2.2 3.2 − 1.2 1168 +1418 + 99 + 23.2 −1038 14 − 2 4.2 − 1.5 4.9 +5.4 −3.0 4727 2.6 +3.4 + 36.5 −1.7 3.5 − 2.3 754 +3573 + 161 + 60.7 − 701 12 − 6 5.8 − 3.9 4.4 +5.6 −2.9 4728 2.3 +3.0 + 24.8 −1.5 4.5 − 2.6 609 +1681 + 117 + 39.8 − 534 17 − 6 7.3 − 4.2 3.7 +4.8 −2.4 0784,4727,4728 844 +1399 + 74 + 25.4 − 454 14 − 3 5.8 − 2.0 4.3 +3.0 −1.6 CXOU J124831.0−054828 (source B) ..... 4728 4.2 +4.6 + 11.7 + 789 + 234 + 19.5 −2.6 2.8 − 0.5 1483 −1244 26 − 2 4.7 − 0.9 7.0 +7.7 −4.2 4729 3.0 +3.9 + 43.5 −2.2 1.8 − 0.8 1662 +2739 −1621 13 +1274 + 69.7 − 2 2.9 − 0.8 4.8 +6.2 −3.5 4730 3.8 +4.2 + 19.0 −2.3 0.6 − 0.1 6320 +1067 + ∞ + 31.1 −6235 22 − 1 1.0 − 0.1 6.2 +6.8 −3.8 4727,4728 1573 +1425 + 649 + 18.4 −1022 20 − 1 3.8 − 0.9 5.9 +4.9 −2.7 4727–4729 3155 +1015 + ∞ + 26.3 −2187 20 − 1 2.9 − 0.5 6.0 +4.0 −2.2 CXOU J124839.0−054750 (source C) ..... 0784 2.8 +3.7 + 85.4 + 74 + 220 −1.9 36.5 −10.9 78 − 52 76 − 20 48.5 +113.5 − 14.5 3.8 +4.9 −2.5 4727 2.1 +3.3 −1.5 37.1 +116.3 + 226 + 382 −26.0 57 − 42 96 − 63 61.8 +193.5 − 43.3 3.5 +5.5 −2.5 + 119 + 220 0784,4727 68 − 33 86 − 33 55.2 +112.2 − 22.8 3.7 +3.7 −1.8 122
duration, ∆tflat, beginning at a given time, t0,flat. Outside of the flare duration, we assumed a constant persistent source rate rpersistent. For a given model flare rate rflat, duration ∆tflat, and beginning time t0,flat, we performed 200,000 Monte Carlo simulations. We varied the model parameters until we found the model that was most likely to have reproduced the observed flare properties. For this best-fit model, the symmetric 90% confidence region for each model parameter was determined from the simulations. The rates and durations were used to calculate X-ray luminosities and fluences for each observation using conversion factors based on the best-fit model for the cumulative X-ray spectrum of all the sources (a power-law with Γ = 1.47; Paper IV). The spectral model was corrected for Galactic absorption and the quantum efficiency degradation for each observation. In Table 4.2, we list the best-fit model properties of the flaring sources. Columns (1) and (2) list the source name and observation number. Columns (3)–(8) list the best-fit flare properties: number of flare photons (nflat), flare rate (rflat), flare duration (∆tflat), ratio of flare rate to persistent rate, flare luminosity (Lflat), and flare fluence (Eflat). Rows with multiple observations listed display the averages of the flare duration, ratio of flare rate to persistent rate, flare luminosity, and flare fluence of the matching flares. Given our limited temporal coverage, it is difficult to place strong limits on the recurrence timescale (∆T ) of the flares. Our simulations show that the probability that our algorithm will detect a flare is only ∼50%. However, the fact that two flares were not seen in any single observation and that there are observations without observed flares for each of the sources implies that ∆T 5 hr. One upper limit on ∆T is given by the shortest observed time between observations with flares; this is 11 days for sources A and B, and 1441 days for source C. However, detections of flares in 123
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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
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Chapter 1 General Introduction 1.1
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Fig. 1.1.— Hubble Tuning Fork, co
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2000). In most HMXBs, the accreted
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not get a complete picture of the L
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this, the result of dynamical inter
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is the Advanced CCD Imaging Spectro
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Chapter 2 Chandra Observations of L
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keV (Sarazin et al. 2000, 2001). Wi
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agreed with positions from the USNO
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24:00 22:00 7:20:00 18:00 16:00 18:
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Table 2.1. Discrete X-ray Sources i
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Table 2.1—Continued Source d Coun
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Table 2.2—Continued Source d Coun
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optical/IR positions of R.A. = 12 h
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log N(>L) 2.0 1.5 1.0 0.5 0.0 NGC 4
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luminosity function for luminositie
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H31 1.0 0.5 0.0 -0.5 -1.0 NGC 4365
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2.4.5 Variability We searched for v
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Number 10 8 6 4 2 NGC 4365 Optical
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LMXBs has an effective radius of 12
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component (“MEKAL”) was used fo
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Table 2.4. X-ray Spectral Fits of N
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Fig. 2.9.— Top panels: Cumulative
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we extended the spectrum down to 0.
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We also examined whether the unreso
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esolved sources in the galaxy. This
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temperature ∼0.3 keV. Matsumoto e
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log I X (counts/sec/arcmin 2 ) -1.0
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∼45% of the counts are resolved i
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Chapter 3 Chandra Observations of D
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noninteracting members (de Vaucoule
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used for spectroscopic analysis. We
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02:00.0 03:00.0 04:00.0 05:00.0 06:
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Page 89 and 90: Table 3.1—Continued d a Count Rat
Page 91 and 92: We also attempted detections in mul
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Page 95 and 96: Fig. 3.3.— Histogram of the obser
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Page 105 and 106: counts occur within ∼ 4 ks. Sourc
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Page 109 and 110: tion), and βouter = 0.36 +0.01 −
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Page 113 and 114: group, we assumed that they were at
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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
Page 121 and 122: 90% confidence level errors. Bracke
Page 123 and 124: we adopted the power-law model as o
Page 125 and 126: sources could be a non-trivial sour
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Page 129 and 130: Fig. 3.13.— Estimated gas and gra
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Page 133 and 134: NGC 1600 that has a small spatial s
Page 135 and 136: (HMXBs). LMC X-4, an HMXB pulsar, h
Page 137 and 138: searched for the shortest time tn o
Page 139: with NGC 4697. Columns (1)-(4) list
Page 143 and 144: the uncertainties quoted do not inc
Page 145 and 146: to persistent rate for short flares
Page 147 and 148: Chapter 5 Multi-Epoch Chandra X-ray
Page 149 and 150: the field, these different populati
Page 151 and 152: luminous (MB < −20) elliptical (E
Page 153 and 154: Although Chandra is known to encoun
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Page 157 and 158: Fig. 5.3.— Adaptively smoothed Ch
Page 159 and 160: 1 × 10 −5 count s −1 arcsec
Page 161 and 162: Table 5.1—Continued Source R.A. D
Page 167 and 168: source list against which to regist
Page 169 and 170: ate from Observation 0784 alone (Pa
Page 171 and 172: Table 5.2. : Optical Properties of
Page 173 and 174: actually be an AGN. Sources 79, 80,
Page 175 and 176: two potential GC counterparts. We l
Page 177 and 178: Table 5.3—Continued X-ray Source
Page 179 and 180: Fig. 5.6.— Color (G475−Z850) -
Page 181 and 182: mass segregation of GCs with the sa
Page 183 and 184: Table 5.4. Fits to the Expected Num
Page 185 and 186: dependence are allowed to vary. Var
Page 187 and 188: NGC 4697 to convert the observed so
Page 189 and 190: 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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