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

More documents

Recommendations

Info

102 CHAPTER 7. OVERALL FEATURE OF X-RAY EMISSION FROM YSOS7.4 Correlation between X-ray and Other Physical Parameters7.4.1 N H vs A VThe relation between the X-ray and visual extinction (N H and A V ) is a key to understand the gasto-dustratio of the interstellar medium, since X-ray and optical–IR photons are mainly absorbedand scattered by interstellar gas and dust, respectively. We find a good log-linear correlation asshown in Figure 7.6. The best-fit linear model (dashed line) isN H(10 21 cm −2 ) = (1.38 ± 0.03)( A V). (7.1)magThe N H /A V ratio of 1.38 is roughly consistent with that of other star-forming clouds; OMC 2/3(1.49: Tsujimoto et al., 2001) and Mon R2 (1.32: Kohno, Koyama, & Hamaguchi, 2002), but slightlylower than that in the average interstellar space of our Galaxy (1.79: Predehl & Schmitt, 1995).This indicates that the gas-to-dust ratio is lower in star-forming clouds than that in the interstellarmedium.Fig. 7.6.— Relation between the absorption column (N H ) and visual extinction (A V : Bontemps etal., 2001, see also TableB.1). Circles, triangles, squares, diamonds, and stars represent class I, classII, class III+III c , unclassified NIR, and BD/BD c sources, respectively. The dashed line shows thebest-fit linear model (see text).
7.4. CORRELATION BETWEEN X-RAY AND OTHER PHYSICAL PARAMETERS 1037.4.2 < L X > vs L bolThe ratio of the X-ray (< L X >) and bolometric (L bol ) luminosities is often used to estimaterelative activity level of X-ray emission of various classes. We show the relation of < L X > andL bol for the ρ Oph X-ray sources with NIR counterpart in Figure 7.7. In the quiescent phase, mostsources have < L X > /L bol of 10 −5 –10 −3 , which is comparable to those for other star-formingclouds (Feigelson et al., 2002; Preibisch & Zinnecker, 2002) and is significantly larger than that forthe quiet sun (∼5×10 −7 : Vaiana & Rosner, 1978). < L X >/L bol for the flare X-rays is also largeand some flares exceed the saturation level of coronally active stars (< L X >/L bol = 10 −3 : Fleminget al., 1995). These results directly indicate that YSOs have much higher X-ray activity level thanMSs. On the other hand, the magnetic B star S1 (= A-41) shows much lower < L X > /L bol value of∼10 −6 than, but almost comparable < L X > of ∼10 29 ergs s −1 to the other (low-mass) YSOs. Thisis consistent with the ASCA results for intermediate-mass YSOs (Herbig Ae/Be stars: Hamaguchi,2001), hence suggests that the X-ray emission mechanism for intermediate-mass YSOs is nearly thesame as that of low-mass YSOs, although the relative X-ray activity level normalized by the totalstellar emission is significantly low. It is also conceivable that S1 shows peculiar spectral features,indicating possible non-thermal emission (see §6.3.5).Fig. 7.7.— Relation between the bolometric (L bol ) and X-ray (< L X >) luminosities for the (left)quiescent and (right) flare phases. Symbols are the same as Figure 7.6. Solid lines represent therelations of < L X >/L bol = 10 −1 , 10 −3 , and 10 −5 . The position of the magnetic B star S1 (=A-41) is indicated in the figure.7.4.3 < L X > vs MassFigure 7.8 shows the relation between < L X > and their stellar mass (M). Within the rangeof M < 2M ⊙ , < L X > seems to be roughly proportional to M, which is the same as another
Page 3:
Contents1 Introduction 12 Review of
Page 9 and 10:
List of Figures2.1 The H-R diagram
Page 11 and 12:
LIST OF FIGURESix6.17 Light curves
Page 13 and 14:
List of Tables3.1 Multiwavelength s
Page 15 and 16:
Chapter 1IntroductionStar formation
Page 17 and 18:
Chapter 2Review of Low-mass Young S
Page 19 and 20:
2.1. EVOLUTION OF LOW-MASS STARS 5w
Page 21 and 22:
2.2. MOLECULAR CLOUDS 72.2 Molecula
Page 23 and 24:
2.3. X-RAY OBSERVATIONS OF LOW-MASS
Page 25 and 26:
Page 27:
Page 30 and 31:
16 CHAPTER 3. REVIEW OF THE ρ OPHI
Page 32 and 33:
Page 34 and 35:
Page 36 and 37:
22 CHAPTER 4. INSTRUMENTATIONrespec
Page 38 and 39:
24 CHAPTER 4. INSTRUMENTATIONangle
Page 40 and 41:
26 CHAPTER 4. INSTRUMENTATIONThe AC
Page 42 and 43:
¨28 CHAPTER 4. INSTRUMENTATIONspli
Page 44 and 45:
30 CHAPTER 4. INSTRUMENTATIONTable
Page 46 and 47:
32 CHAPTER 5. CHANDRA OBSERVATIONS
Page 48 and 49:
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67: 52 CHAPTER 5. CHANDRA OBSERVATIONS
Page 72 and 73: 58 CHAPTER 6. INDIVIDUAL SOURCEShig
Page 74 and 75: 60 CHAPTER 6. INDIVIDUAL SOURCESres
Page 76 and 77: 62 CHAPTER 6. INDIVIDUAL SOURCES6.2
Page 78 and 79: 64 CHAPTER 6. INDIVIDUAL SOURCESfla
Page 80 and 81: 66 CHAPTER 6. INDIVIDUAL SOURCESTab
Page 82 and 83: 68 CHAPTER 6. INDIVIDUAL SOURCESUsi
Page 84 and 85: 70 CHAPTER 6. INDIVIDUAL SOURCESlos
Page 88 and 89: 74 CHAPTER 6. INDIVIDUAL SOURCESdes
Page 90 and 91: 76 CHAPTER 6. INDIVIDUAL SOURCESocc
Page 100 and 101: 86 CHAPTER 6. INDIVIDUAL SOURCEStha
Page 102 and 103: 88 CHAPTER 6. INDIVIDUAL SOURCES1ke
Page 104 and 105: 90 CHAPTER 6. INDIVIDUAL SOURCESThe
Page 106 and 107: 92 CHAPTER 6. INDIVIDUAL SOURCESFig
Page 108 and 109: 94 CHAPTER 6. INDIVIDUAL SOURCESPra
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 118 and 119: 104 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
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?