J/A+A/447/245 Cyg X-1 Spectral Evolution 1999-2004 (Wilms+, 2006)
Long Term Variability of Cyg X-1: IV. Spectral Evolution 1999-2004.
Wilms J., Nowak M.A., Pottschmidt K., Pooley G.G., Fritz S.
<Astron. Astrophys. 447, 245 (2006)>
=2006A&A...447..245W 2006A&A...447..245W
ADC_Keywords: Binaries, X-ray ; Stars, variable
Keywords: stars: individual: Cyg X-1 - stars: binaries: close -
X-rays: binaries - black hole physics
Abstract:
Continuing the observational campaign initiated by our group, we
present the long term spectral evolution of the Galactic black hole
candidate Cygnus X-1 in the X-rays and at 15GHz. We present about 200
pointed observations taken between early 1999 and late 2004 with the
Rossi X-ray Timing Explorer and the Ryle radio telescope. The X-ray
spectra are remarkably well described by a simple broken power law
spectrum with an exponential cutoff. Physically motivated
Comptonization models, e.g., by Titarchuk (1994ApJ...434..570T 1994ApJ...434..570T,
compTT) and by Coppi (1999, eqpair), can reproduce this simplicity;
however, the success of the phenomenological broken power law models
cautions against ``over-parameterizing'' the more physical models.
Broken power law models reveal a significant linear correlation
between the photon index of the lower energy power law and the
hardening of the power law at about 10keV. This phenomenological
soft/hard power law correlation is partly attributable to correlations
of broad band continuum components, rather than being dominated by the
weak hardness/reflection fraction correlation present in the
Comptonization model. Specifically, the Comptonization models show
that the bolometric flux of a soft excess (e.g., disk component) is
strongly correlated with the compactness ratio of the Comptonizing
medium, with Ldisk∝(lh/ls_)-0.19. Over the course of our
campaign, Cyg X-1 transited several times into the soft state, and
exhibited a large number of ``failed state transitions''. The fraction
of the time spent in such low radio emission/soft X-ray spectral
states has increased from about 10% in 1996-2000 to about 34% since
early 2000. We find that radio flares typically occur during state
transitions and failed state transitions (at lh/ls∼3), and that
there is a strong correlation between the 10-50keV X-ray flux and the
radio luminosity of the source. We demonstrate that rather than there
being distinctly separated states, in contrast to the timing
properties the spectrum of Cyg X-1 shows variations between extremes
of properties, with clear cut examples of spectra at every
intermediate point in the observed spectral correlations.
Objects:
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RA (2000) DE Designation(s)
----------------------------------------------------------
19 58 21.7 +35 12 06 Cyg X-1 = V* V1357 Cyg
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 388 202 Best-fit results for the broken power-law model
table1.fit 2880 31 FIT version of table1
table2.dat 394 202 Best-fit results for the compTT models
table2.fit 2880 31 FIT version of table2
table3.dat 494 202 Best-fit results for the eqpair models
table3.fit 2880 34 FIT version of table3
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See also:
J/AZh/78/408 : Variability of Cyg X-1 in 1994-1998 (Karitskaya+, 2001)
J/PAZh/26/27 : Variability of Cyg X-1 (V1357) in 1995-1996 (Karitskaya+, 2000)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 "date" ObsStart Date of the start of the observation,
YYYY-MM-DDThh:mm:ss
21- 39 A19 "date" ObsEnd Date of the end of the observation,
YYYY-MM-DDThh:mm:ss
41- 48 F8.2 d MJDStart MJD of the start of observation
50- 57 F8.2 d MJDStop MJD of the end of observation
59- 63 I5 s ExpTime Exposure time
65- 70 F6.1 ct/s CR Count rate
72- 78 F7.5 ct/s e_CR rms uncertainty on CR
80- 85 F6.4 cm-2/s Fph(2-5) 2-5keV band photon flux (G1)
87- 96 E10.5 mW/m2 Fene(2-5) 2-5keV band energy flux
98-103 F6.4 cm-2/s Fph(5-10) 5-10keV band photon flux (G1)
105-114 E10.5 mW/m2 Fene(5-10) 5-10keV energy flux
116-123 F8.6 cm-2/s Fph(10-50) 10-50keV band photon flux (G1)
125-134 E10.5 mW/m2 Fene(10-50) 10-50keV band energy flux
136-144 F9.7 cm-2/s Fph(50-100) 50-100keV band photon flux (G1)
146-155 E10.5 mW/m2 Fene(50-100) 50-100keV band energy flux
158-163 F6.4 cm-2/s Fph(2-100) 2-100keV band photon flux (G1)
165-174 E10.5 mW/m2 Fene(2-100) 2-100keV band energy flux
176-182 F7.3 --- chi2 chi2 value
183-185 I3 --- DOF Degree of freedom
187-193 F7.5 --- chi2red Reduced chi2 value
196-205 E10.8 10+22cm-2 nH Hydrogen column density
207-215 F9.7 10+22cm-2 e_nH 90% uncertainty range on nH
217-226 F10.7 keV cutoffE Cutoff energy
228-238 F11.8 keV e_cutoffE 90% uncertainty range on cutoffE
240-246 F7.3 keV FoldE Folding energy
247-253 F7.3 keV e_FoldE 90% uncertainty range on FoldE
255-260 F6.4 keV lineE Fe Kalpha line energy
262-267 F6.4 keV e_lineE 90% uncertainty range on LineE
269-279 F11.9 keV lineEsigma Fe Kalpha width (sigma)
282-290 F9.7 keV e_lineEsigma 90% uncertainty range on lineEsigma
292-300 F9.7 --- lineEN Fe Kalpha norm (total photons in line)
302-310 F9.7 --- e_lineEN 90% uncertainty range on lineEN
312-317 F6.4 --- PI1 Photon index below break energy
319-324 F6.4 --- e_PI1 90% uncertainty range on PI1
326-332 F7.4 keV BreakE Break energy
334-340 F7.4 keV e_BreakE 90% uncertainty range on BreakE
342-347 F6.4 --- PI2 Photon index above break energy
349-354 F6.4 --- e_PI2 90% uncertainty range on PI2
357-363 F7.4 --- bknpowerN Photon flux of bkn powerlaw at 1keV
365-372 F8.5 --- e_bknpowerN 90% uncertainty range on bknpoweN
374-380 F7.5 --- Factor Flux normalization factor
382-388 F7.5 --- e_Factor 90% uncertainty range on Factor
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 "date" ObsStart Date of the start of the observation,
YYYY-MM-DDThh:mm:ss
21- 39 A19 "date" ObsEnd Date of the end of the observation,
YYYY-MM-DDThh:mm:ss
41- 48 F8.2 d MJDStart MJD of the start of observation
50- 57 F8.2 d MJDStop MJD of end of observation
59- 63 I5 s ExpTime Exposure time
65- 70 F6.1 ct/s CR Count rate
72- 78 F7.5 ct/s e_CR rms uncertainty on CR
80- 85 F6.3 cm-2/s FphDisk Accretion disk unabsorbed photon
flux (G1)
87- 96 E10.5 mW/m2 FeneDisk Accretion disk unabsorbed energy flux
98-103 F6.3 cm-2/s FphTotal Bolometric unabsorbed photon flux (G1)
105-114 E10.5 mW/m2 FeneTotal Bolometric unabsorbed energy flux
116-121 F6.4 cm-2/s Fph(2-5) 2-5keV band photon flux (G1)
123-132 E10.5 mW/m2 Fene(2-5) 2-5keV band energy flux
134-139 F6.4 cm-2/s Fph(5-10) 5-10keV band photon flux (G1)
141-150 E10.5 mW/m2 Fene(5-10) 5-10keV energy flux
152-159 F8.6 cm-2/s Fph(10-50) 10-50keV band photon flux (G1)
161-170 E10.5 mW/m2 Fene(10-50) 10-50keV band energy flux
172-180 F9.7 cm-2/s Fph(50-100) 50-100keV band photon flux (G1)
182-191 E10.5 mW/m2 Fene(50-100) 50-100keV band energy flux
193-198 F6.2 --- chi2 chi2 value of the best fit
200-202 I3 --- DOF Degree of freedom
204-210 F7.5 --- chi2red Reduced chi2 value
212-221 E10.8 10+22cm-2 nH Hydrogen column density
223-231 F9.7 10+22cm-2 e_nH 90% uncertainty range on nH
233-239 F7.5 keV Tin Inner disk temperature
241-247 F7.5 keV e_Tin 90% uncertainty range on Tin
249-255 F7.2 --- diskbbN Norm of disk (see XSPEC manual)
257-264 F8.3 --- e_diskbbN 90% uncertainty range on diskbbN
266-272 F7.3 keV kT Temperature of Comptonizing plasma
274-281 F8.3 keV e_kT 90% uncertainty range on kT
283-290 F8.6 --- taup Optical depth of Comptonizing plasma
292-300 F9.6 --- e_taup 90% uncertainty range on taup
302-310 F9.7 --- compTTN Norm of compTT model
312-321 F10.7 --- e_compTTN 90% uncertainty range on compTTN
323-332 F10.7 --- Refl omega/2pi for the reflecting medium
334-342 F9.6 --- e_Refl 90% uncertainty range on Refl
344-350 F7.5 keV Reflsigma omega/2pi for the reflecting
medium (sigma)
352-358 F7.5 keV e_Reflsigma 90% uncertainty range on Reflsigma
360-368 F9.7 --- ReflN omega/2pi for the reflecting medium
norm
370-378 F9.7 --- e_ReflN 90% uncertainty range on ReflN
380-386 F7.5 --- Factor Flux normalization factor
388-394 F7.5 --- e_Factor 90% uncertainty range on Factor
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 "date" ObsStart Earliest time entering observation,
YYYY-MM-SSThh:mm:ss
22- 40 A19 "date" ObsEnd Latest time entering observation,
YYYY-MM-SSThh:mm:ss
42- 49 F8.2 s MJDStart MJD of the start of observation
51- 58 F8.2 s MJDStop MJD of the end of observation
60- 64 I5 s TimeExp Exposure time of each file
66- 71 F6.1 ct/s CR Count rate of each file
73- 79 F7.5 ct/s e_CR rms uncertainty of each count rate
81- 86 F6.3 cm-2/s FphDisk Accretion disk unabsorbed photon
flux (G1)
88- 97 E10.5 mW/m2 FeneDisk Accretion disk unabsorbed energy flux
99-104 F6.3 cm-2/s FphTotal Bolometric unabsorbed photon flux (G1)
106-115 E10.5 mW/m2 FeneTotal Bolometric unabsorbed energy flux
118-123 F6.4 cm-2/s Fph(2-5) 2-5keV band Photon flux (G1)
126-135 E10.5 mW/m2 Fene(2-5) 2-5keV band Energy flux
140-145 F6.4 cm-2/s Fph(5-10) 5-10keV band Photon flux (G1)
147-156 E10.5 mW/m2 Fene(5-10) 5-10keV band Energy flux
159-166 F8.6 cm-2/s Fph(10-50) 10-50keV band Photon flux (G1)
169-178 E10.5 mW/m2 Fene(10-50) 10-50keV band Energy flux
181-189 F9.7 cm-2/s Fph(50-100) 50-100keV Photon flux (G1)
192-201 E10.5 mW/m2 Fene(50-100) 50-100keV band Energy flux
204-209 F6.2 --- chi2 Chi-squared value of the best fit
212-214 I3 --- DOF Degrees of freedom
217-223 F7.5 --- chi2red Reduced Chi-squared
226-235 E10.8 10+22cm-2 nH Hydrogen column density
238-246 F9.7 10+22cm-2 e_nH 90% uncertainty range of nH parameter
249-255 F7.5 keV Tin Innner disk temperature
258-264 F7.5 keV e_Tin 90% uncertainty range of Tin parameter
267-277 F11.5 --- DiskbbN norm of the disk
280-290 F11.5 --- e_DiskbbN 90% uncertainty range of DiskbbN
293-298 F6.4 keV LineE Fe Kalpha line energy
301-306 F6.4 keV e_LineE 90% uncertainty range of LineE
309-315 F7.5 keV LineEsigma Fe Kalpha line width
318-325 F8.6 keV e_LineEsigma 90% uncertainty range of LineEsigma
328-336 F9.7 --- LineEN Fe Kalpha norm (total photons in line)
339-347 F9.7 --- e_LineEN 90% uncertainty range of LineEN
350-356 F7.5 --- lhls Ratio of hard to soft compactness
359-365 F7.5 --- e_lhls 90% uncertainty range of lhls
368-374 F7.5 --- taup optical depth of Comptonizing plasma
377-383 F7.5 --- e_taup 90% uncertainty range of taup
386-395 E10.7 --- Refl Omega/2pi for reflecting medium
398-405 F8.6 --- e_Refl 90% uncertainty range of Refl
408-420 E13.12 --- xi Ionization parameter of reflector
423-430 F8.3 --- e_xi 90% uncertainty range of xi
439-447 F9.7 --- eqpairN Norm of eqpair model
450-460 F11.8 --- e_eqpairN 90% uncertainty range of eqpairN
471-477 F7.5 --- Factor Flux normalization factor
488-494 F7.5 --- e_Factor 90% uncertainty range of Factor
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Global notes:
Note (G1): in ph/cm2/s
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Acknowledgements: Joern Wilms, j.wilms(at)warwick.ac.uk
(End) Patricia Vannier [CDS] 17-Oct-2005