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

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produced by the accretion footprint. The hydrogen gas is excited and/or ionized, and recombination of the ionized hydrogen and spontaneous emission from excited atoms produces the characteristic observed hydrogen emission lines. 13
CHAPTER II ERUPT<strong>IN</strong>G <strong>YOUNG</strong> STARS 2.1 T Tauri Stars There are literally dozens of variable star classes. The majority of these, however, involve fully formed main-sequence stars or, as in the case of many single star systems, stars that have evolved o↵ the main sequence. Some of these variable star classes consist of binary systems in which the components are physically interacting with one another, typically causing the total observed flux to vary sporadically or quasi- periodically. Other binary systems have components that are distant enough from one another that they only interact gravitationally with one another. In these cases, the stars’ orbital geometry causes them to eclipse one another, periodically varying the observed flux. Still other variable star classes involve single, evolved stars that pulsate. There are fewer variable star classes that exist which consist of very young objects that have not reached the main sequence. This is often because these objects are still deeply embedded in dusty regions, making many of them very di cult to observe or even notice in the first place. When discussing the final formation of low-mass (2M and smaller) stars, these objects are often grouped into a category of stars known as T Tauri stars (TTSs), named after the prototype T Taurus. T Taurus, or “T Tau”, was first noted in 1852 by John Russel Hind (Barnard, 1895). Joy (1945) suggested that this star, along with ten others, should comprise a separate class of variable stars based on 14
Page 1 and 2: EVIDENCE OF ACCRETION-GENERATED X-R
Page 3 and 4: 4.3.2. Spectral Modeling . . . . .
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: perturbations or disk instabilities
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
Page 53 and 54: pixels or pixel columns. • Parame
Page 55 and 56: deal of built-in flexibility in how
Page 57 and 58: accrete most of their mass (Hartman
Page 59 and 60: 4.2 Observations & Data Reduction O
Page 61 and 62: were grouped into energy bins with
Page 63 and 64: Since V1647 Ori was imaged with bot
Page 65 and 66: 4.3 Results 4.3.1 Short-Term and Lo
Page 67 and 68: overall X-ray light curve, the soft
Page 69 and 70: Count Rate (cts/s) Count Rate (cts/
Page 71 and 72: Count Rate (cts/s) Count Rate (cts/
Page 73 and 74:
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
Page 113 and 114:
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
Page 127 and 128:
Figure 29 shows the three CXO spect
Page 129 and 130:
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,
Page 147 and 148:
Orlando, S., Peres, G., & Reale, F.
Page 149:
Venkat, V. & Anandarao, B. G. 2011,
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