observational overview of state transitions in x-ray binaries

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SPECTRAL EVOLUTION hardness-intensity diagram (HID) The arrows indicate the evolution in time. The source starts out faint and hard and increases in luminosity while the spectrum remains hard. At some point a sudden softening of the spectrum takes place, with only minor changes in the count rate. The spectrum remains soft as the source decays, but at some point the spectrum shows a sudden hardening and returns to the same hardness as at the start of the outburst. For the remainder of the decay the spectrum remains hard. The q-shaped diagram is traced out in an anti-clockwise manner. There are two important aspect of this diagram that should be noted. First, while at low luminosities the spectrum is always hard, at higher luminosities, the spectrum can be hard, soft, or of intermediate hardness. Second, the transition from hard to soft takes place at a significantly higher luminosity than the reverse transition. Similar behavior is also seen in other sources, as I will show later.
Luminosity (erg/s) SPECTRAL EVOLUTION ux hardness 1- Disk Fraction Dunn et al. 2010 Alternative ways to trace the evolution that actually involve some spectral fitting, produce similar looking diagrams. Here I’m showing a figure taken from a paper by Dunn et al. It show a so-called disk-fraction-luminosity diagram, where disk fraction is defined as the ratio of disk flux and total flux. It is useful to compare outbursts of different sources, but it requires a lot more work and is less sensitive to subtle changes. For comparison they show how certain selected observations in a HID map onto such a diagram - it clearly show the limitation to constrain disk fraction with RXTE, which is the reason I prefer to stick with the HID.
Page 1 and 2: !""#$%&'()*#'"$++$+)&(),-#!.+/ 4566
Page 3 and 4: MORE BACKGROUND • 1996>: Dedicate
Page 5 and 6: TRANSIENT SOURCES • Relation betw
Page 7 and 8: OUTBURST LIGHT CURVES 4U 1543-47 GR
Page 9 and 10: ENERGY DEPENDENCE This movie (Homan
Page 11 and 12: SPECTRAL EVOLUTION GX 339-4 First I
Page 13: COLOR EVOLUTION hardness-intensity
Page 17 and 18: XTE J1752-223 XTE J1908+094 SPECTRA
Page 19 and 20: SPECTRAL EVOLUTION GRO J1655-40 I
Page 21 and 22: SPECTRAL EVOLUTION GRO J1655-40 We
Page 23 and 24: SPECTRAL EVOLUTION GX 339-4 Transit
Page 25 and 26: IMPLICATIONS FOR ACCRETION • outb
Page 27 and 28: STATE CLASSIFICATION • Various cl
Page 29 and 30: RAPID X-RAY VARIABILITY • power d
Page 31 and 32: • low-luminosity version of the h
Page 33 and 34: INTERMEDIATE STATE Intermediate (tr
Page 35 and 36: RAPID X-RAY VARIABILITY Okay, let
Page 37 and 38: Power type-B frequency up 1 10 100
Page 39 and 40: No Compact Jet (interaction with IS
Page 41 and 42: GRO J1655-40 weak abs. lines weak e
Page 43 and 44: Aql X-1 NEUTRON STARS hard - soft -
Page 45 and 46: Aql X-1 Back to the HID again. NEUT
Page 47 and 48: hard transitional Lin et al. 2009 H
Page 49 and 50: Lin et al. 2009 Homan et al. 2010 N

observational overview of state transitions in x-ray binaries

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