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

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94 CHAPTER 6. INDIVIDUAL SOURCESPravdo et al. 2001; Favata et al. 2002; see also Figure 2.9). Although CRBR85 has shown no evidencefor outflow activity, bipolar nebulosity was detected, indicating the existence of an edge-oncircumstellar disk (Brandner et al., 2000). We therefore suspect that jet-induced X-rays with alarge offset from the central source are possible because of the large inclination angle.BF-S7CRBR85Fig. 6.29.— Close-up ACIS image around BF-S7and CRBR85. Circles represent the position ofBF-S7 and CRBR85. Filled squares correspondto one X-ray photon.5arcsec6.6.6 BF-H3A hard-band source BF-H3 has no NIR counterpart, but is associated with an optical [S II ] sourceA2, a candidate of HH (Gómez et al., 1998). Hence BF-H3 may be the third sample of X-rayemitting HHs following HH2 (Pravdo et al., 2001) and L1551 IRS5 (Favata et al., 2002), althoughthere is no other evidence for its HH nature and for the origin of A2. Interestingly, BF-H3 showsX-ray emission only in the hard band (2.0–9.0 keV), hence would have much higher temperatureplasma (2 keV) than that of L1551 IRS5 and HH2 (0.1–0.5 keV). This indicates high-velocityoutflow activity, which is the similar case to GY91 (§6.1.1).
Chapter 7Overall Feature of X-ray Emissionfrom YSOs7.1 X-ray Detection RateWe detected 195 X-ray sources from the ∼1 pc × 2 pc region of the ρ Oph main body. About60% (110) of them are identified with NIR sources. Table 7.1 summarizes the number of X-raysources and detection rate for each class.High detection rate (≥ 50%) is obtained for class Isources as well as class II and III sources, while that is slightly lower for class III c , BD, and BD csources (< 40%). Figure 7.1 shows the relation between the bolometric luminosity (L bol ) and visualextinction (A V ) for the ρ Oph sources (Table B.1). We see the tendency that most sources with noX-ray detection (gray symbols in Figure 7.1) are distributed at the upper-left area in this figure,i.e., having relatively lower L bol and higher A V . Considering the almost constant < L X >/L boland N H /A V correlations (§7.4.1 and §7.4.2), this means that the X-ray non-detected sources havelower < L X > and higher N H even if they emit X-rays. It hence would be conceivable that theX-ray non-detected sources may emit X-rays below the current sensitivity limit of Chandra. Lowerdetection rate of class III c , BD, and BD c sources is simply due to lower L bol ( ∼ = lower < L X >) ofthese classes. On the other hand, X-ray non-detected class I sources have relatively high L bol withmoderate A V (e.g., GSS30, G304, and GY378; Figure 7.1). However, this could be partly due toshort time variability. For example, WL21 (BF-8) and GY256 (BF-51) are hardly visible exceptwhen they exhibit X-ray flares (see Figure A.1). Also long-term variability, like the 11-year cycleof the solar X-ray activity, may exist. We therefore expect that virtually all YSOs, at least in ρOph, are potential X-ray emitters regardless of their classes.95
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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 58 and 59: 44 CHAPTER 5. CHANDRA OBSERVATIONS
Page 72 and 73: 58 CHAPTER 6. INDIVIDUAL SOURCEShig
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Page 76 and 77: 62 CHAPTER 6. INDIVIDUAL SOURCES6.2
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Page 106 and 107: 92 CHAPTER 6. INDIVIDUAL SOURCESFig
Page 110 and 111: 96 CHAPTER 7. OVERALL FEATURE OF X-
Page 112 and 113: 98 CHAPTER 7. OVERALL FEATURE OF X-
Page 114 and 115: 100 CHAPTER 7. OVERALL FEATURE OF X
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
Page 140 and 141: 126 APPENDIX B. PHYSICAL PARAMETERS
Page 142 and 143: 128 APPENDIX B. PHYSICAL PARAMETERS
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., &
Page 153 and 154: BIBLIOGRAPHY 139Johnstone, D., Wils
Page 155 and 156: BIBLIOGRAPHY 141Rutledge, R. E., Ba
Page 157: BIBLIOGRAPHY 143Yokoyama, T. & Shib
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X-ray Study of Low-mass Young Stellar Objects in the ρ Ophiuchi ...

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