X-ray Study of Low-mass Young Stellar Objects in the ρ Ophiuchi ...

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88 CHAPTER 6. INDIVIDUAL SOURCES1keVA-291keVA-31FlareBF-3610keV5keV5keVQuiescent10keVSMMJ16264-2424KSHK-ASMMJ16267-2430Fig. 6.22.— The relation between the X-ray ionization rate and the distance from the source for(left) A-29, (middle) A-31, and (right) BF-36. For A-29 and A-31, we represent three lines for theflare phase with the assumed temperatures (1, 5, and 10 keV). For BF-36, the flare and quiescentphases are separately estimated. Dashed and dash-dotted lines represent the ionization rate fromcosmic rays and the core radii.
6.6. UNIDENTIFIED SOURCES 896.6 Unidentified Sources6.6.1 Overall featureIn order to examine the average feature of unidentified sources, we co-add and make compositespectra, separately for total-band, soft-band, and hard-band sources (hereafter, we call them “totalbandunidentified sources” and so on). We do not include A-29, A-31, BF-36, A-75 = BF-11, BF-92,BF-S7, and BF-H3 because they have different nature from the other unidentified sources. A-H2 isalso excluded because of severe contamination from A-2 (DoAr21). Figure 6.23 shows the compositespectra. First we fit them by the MEKAL model. However, uncomfortably high temperature (>20 keV) is obtained for the total- and hard-band unidentified sources. We hence re-fit them by apower-law model and find acceptable fits. Figure 6.23 (solid lines) and Table 6.7 show the best-fitmodels and parameters, respectively.Fig. 6.23.— Composite spectra of (a) total-band, (b) soft-band, and (c) hard-band unidentifiedsources. The upper panels show data points (crosses) and the best-fit non-thermal (a and c) andthermal (b) model (solid line), while the lower panels are the data residuals from the best-fit model.Circles and triangles represent the data for obs-A and obs-BF, respectively.The best-fit photon index (∼1.5) of the total-band unidentified sources is similar to that ofthe canonical value of active galactic nuclei (AGNs: ∼1.7), while the best-fit N H of 5.3×10 22 cm −2is nearly equal to the average value through this cloud (Tachihara et al., 2000). Inversely, if thebackground sources have a mean photon index of 1.5 and are absorbed by the cloud gas of N H =5.3×10 22 cm −2 , the log N – log S relation by Mushotzky et al. (2000) predicts the detectable sourcenumbers to be several tens, which is consistent with the total number of unidentified sources (∼80).Also, the spatial distribution of the total-band unidentified sources seems to be anti-correlated withthe molecular cloud (Figure 6.24). Most of the total-band unidentified sources therefore are likelyto be background AGNs, as well as the radio bright unidentified source A-75/BF-11 = LFAM21(§6.6.3).
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Contents1 Introduction 12 Review of
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List of Figures2.1 The H-R diagram
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LIST OF FIGURESix6.17 Light curves
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List of Tables3.1 Multiwavelength s
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Chapter 1IntroductionStar formation
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Chapter 2Review of Low-mass Young S
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2.1. EVOLUTION OF LOW-MASS STARS 5w
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2.2. MOLECULAR CLOUDS 72.2 Molecula
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2.3. X-RAY OBSERVATIONS OF LOW-MASS
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16 CHAPTER 3. REVIEW OF THE ρ OPHI
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22 CHAPTER 4. INSTRUMENTATIONrespec
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24 CHAPTER 4. INSTRUMENTATIONangle
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26 CHAPTER 4. INSTRUMENTATIONThe AC
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¨28 CHAPTER 4. INSTRUMENTATIONspli
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30 CHAPTER 4. INSTRUMENTATIONTable
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32 CHAPTER 5. CHANDRA OBSERVATIONS
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Page 121 and 122: Chapter 8Systematic Study of YSO Fl
Page 123 and 124: 8.2. CORRELATION BETWEEN THE FLARE
Page 125 and 126: 8.3. MAGNETIC RECONNECTION MODEL 11
Page 127 and 128: 8.5. EFFECT OF THE QUIESCENT X-RAYS
Page 129 and 130: 8.6. EVOLUTION OF YSOS AND THEIR FL
Page 131 and 132: Chapter 9ConclusionWe summarize the
Page 133 and 134: Appendix AFlare Light CurvesFig. A.
Page 135 and 136: Fig.A.2 (Continued)121
Page 137: Fig. A.4.— Same as Figure A.1, bu
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Page 145 and 146: Appendix CModeling of the FlareIn t
Page 147 and 148: C.2. PREDICTED CORRELATIONS BETWEEN
Page 149 and 150: BibliographyAgeorges, N., Eckart, A
Page 151 and 152: BIBLIOGRAPHY 137Feigelson, E. D., &
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BIBLIOGRAPHY 139Johnstone, D., Wils
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BIBLIOGRAPHY 141Rutledge, R. E., Ba
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BIBLIOGRAPHY 143Yokoyama, T. & Shib
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