EVIDENCE OF ACCRETION-GENERATED X-RAYS IN THE YOUNG ...

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Table of Contents Page ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Chapter I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1. An Overview of Star Formation . . . . . . . . . . . . . . . . . . 3 1.1.1. Circumstellar Disks . . . . . . . . . . . . . . . . . . . . . 6 1.1.2. Circumstellar Accretion . . . . . . . . . . . . . . . . . . . 11 II. ERUPTING YOUNG STARS . . . . . . . . . . . . . . . . . . . . . . 14 2.1. T Tauri Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2. FUors and EXors . . . . . . . . . . . . . . . . . . . . . . . . . . 17 III. X-RAY ASTRONOMY: A TOOL FOR STUDYING YOUNG STARS 24 3.1. Previous X-ray Work . . . . . . . . . . . . . . . . . . . . . . . . 24 3.1.1. X-ray Production & Rotation . . . . . . . . . . . . . . . 25 3.1.2. X-ray Production & Coronal Structures . . . . . . . . . . 28 3.1.3. X-ray Production & Accretion . . . . . . . . . . . . . . . 29 3.1.4. Gleaning Other Information from X-rays . . . . . . . . . 30 3.2. The Chandra X-ray Observatory . . . . . . . . . . . . . . . . . . 33 3.2.1. The High Resolution Mirror Assembly . . . . . . . . . . . 35 3.2.2. High- and Low-Energy Transmission Gratings . . . . . . 36 3.2.3. HRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.2.4. ACIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.2.5. Other Instruments of Note . . . . . . . . . . . . . . . . . 42 3.3. From the Telescope to Science Results -CXO Data Reduction . . 42 IV. X-RAY PRODUCTION BY V1647 ORI DURING OPTICAL OUT- BURSTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.2. Observations & Data Reduction . . . . . . . . . . . . . . . . . . 50 4.3. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.3.1. Short-Term and Long-Term Variability . . . . . . . . . . 56 i
4.3.2. Spectral Modeling . . . . . . . . . . . . . . . . . . . . . . 72 4.4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 4.4.1. Observations of Hotter and Cooler X-ray-Generating Plasmas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 4.4.2. Possibility of a Second Plasma . . . . . . . . . . . . . . . 91 4.4.3. Similarity of the 2003 and 2008 Eruptions . . . . . . . . . 93 4.5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 V. DETECTION OF A COOL, ACCRETION SHOCK-GENERATED X-RAY PLASMA IN EX LUPI DURING THE 2008 OPTICAL ERUP- TION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.2. Observations & Data Reduction of X-ray Data . . . . . . . . . . 102 5.3. Results from X-ray Observations . . . . . . . . . . . . . . . . . . 106 5.3.1. General Spectral Characteristics Indicating Accretion . . 106 5.3.2. Spectral Modeling . . . . . . . . . . . . . . . . . . . . . . 106 5.3.3. The Temporal Evolution of the Post-Outburst X-ray Plasma116 5.4. Optical Variability During the 2008 Outburst . . . . . . . . . . . 123 5.5. Discussion & Conclusions . . . . . . . . . . . . . . . . . . . . . . 128 VI. DISCUSSION AND CONCLUSIONS . . . . . . . . . . . . . . . . . . 130 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 ii
Page 1: EVIDENCE OF ACCRETION-GENERATED X-R
Page 5 and 6: the first time through a telescope,
Page 7 and 8: List of Tables Table Page 1. 2002-2
Page 9 and 10: 19. Correlation Between Changes in
Page 11 and 12: on Earth, nay, the entire solar sys
Page 13 and 14: known as a molecular cloud. These s
Page 15 and 16: internal pressure will be overcome.
Page 17 and 18: With advancements in telescope and
Page 19 and 20: the circumstellar disk, such as the
Page 21 and 22: perturbations or disk instabilities
Page 23 and 24: CHAPTER II ERUPTING YOUNG STARS 2.1
Page 25 and 26: (1997). Once the TTS spectral class
Page 27 and 28: Annu. Rev. Astro. Astrophys. 1996.3
Page 29 and 30: FUors have typical accretion rates
Page 31 and 32: and radiative equilibrium and that
Page 33 and 34: CHAPTER III X-RAY ASTRONOMY: A TOOL
Page 35 and 36: of the X-ray luminosity (LX) totheb
Page 37 and 38: filtered light curves (which had la
Page 39 and 40: 3.1.4 Gleaning Other Information fr
Page 41 and 42: Fig. 9a ~6.4 keV ~6.7 keV Figure 8:
Page 43 and 44: 34 Figure 9: Schematic of the Chand
Page 45 and 46: Figure 10: Schematic of the Chandra
Page 47 and 48: Top View Rowland Circle Grating fac
Page 49 and 50: electrons eventually exits the outp
Page 51 and 52: one to e↵ectively determine the e
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pixels or pixel columns. • Parame
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deal of built-in flexibility in how
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accrete most of their mass (Hartman
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4.2 Observations & Data Reduction O
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were grouped into energy bins with
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Since V1647 Ori was imaged with bot
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4.3 Results 4.3.1 Short-Term and Lo
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overall X-ray light curve, the soft
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Count Rate (cts/s) Count Rate (cts/
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The highest measured X-ray mean cou
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during short-term variability, howe
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Change in Mean Hardness Ratio 1 0.5
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These results suggest that we can i
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Table 3. Model Fits for 2008-2009 C
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For the CXO observations of V1647 O
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normalized counts s −1 keV −1
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Determining a robust model for the
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April 4 XMM observation (109 eV) an
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s −1 ) Log Observed Flux (ergs cm
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tures of a few million Kelvin (kTX
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2004 March, especially if the large
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and AK =0.5on2004Feburary18,allofwh
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In order to test whether CXO would
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• and X-ray luminosities that are
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With V1647 Ori being observed inten
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level approximately one year after
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of an object in which this process
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eduction. In §3, we discuss the re
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Table 5. Chandra ACIS Observations
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5.3 Results from X-ray Observations
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y an intervening column of hydrogen
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Table 6. Best-Fit Models for EX Lup
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component plasma, subject to a sing
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does require a third, heavily-absor
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5.3.3 The Temporal Evolution of the
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Figure 29 shows the three CXO spect
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From 2008 June to August, the plasm
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June, however, the X-ray flux from
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to test this light curve for possib
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We note that in the above analysis,
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5.5 Discussion & Conclusions The op
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CHAPTER VI DISCUSSION AND CONCLUSIO
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sensitive line diagnostics that wou
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Bell, K. R., Lin, D. N. C., & Ruden
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Hartmann, L. & Kenyon, S. J. 1996,
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Orlando, S., Peres, G., & Reale, F.
Page 149:
Venkat, V. & Anandarao, B. G. 2011,
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EVIDENCE OF ACCRETION-GENERATED X-RAYS IN THE YOUNG ...

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