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J/A+A/452/975       Temporal variability of Cygnus X-1       (Axelsson+, 2006)
Probing the temporal variability of Cygnus X-1 into the soft state.
    Axelsson M., Borgonovo L., Larsson S.
   <Astron. Astrophys. 452, 975 (2006)>
   =2006A&A...452..975A
ADC_Keywords: Accretion ; Binaries, X-ray ; X-ray sources

Keywords: Accretion, accretion disks ; Stars: individual: Cyg X-1 ;
          X-rays: binaries

Abstract:
    We present results of fitting power density spectra from archived
    Rossi X-ray Timing Explorer (RXTE) data of the source Cygnus X-1. 
    The data cover the observations of the source during 1996-2003, 
    and all spectral states are included.

Description:
    This file contains the results of the fits of two Lorentzians and a
    cut-off power-law to the X-ray power density spectra of Cygnus X-1.
    The power spectra in all spectral states of the source are fitted with
    this model. The majority of the data were first presented in Axelsson
    et al. (2005A&A...438..999A), but is included as Table 1 in Axelsson
    et al. (2006A&A...452..975A).

    Note that some data has been refitted after further analysis as
    described in Axelsson et al. (2006A&A...452..975A), and some time
    ranges therefore overlap. In addition, in the refitted cases one
    parameter was frozen to the value given in the table. The error-bars
    of this parameter (W1) are here equal to exactly zero.

    Parameters of components which were not present in the fit are
    identified by setting them to exactly zero.
Objects:
    -----------------------------------------------
       RA   (2000)   DE      Designation(s)
    -----------------------------------------------
    19 58 21.7   +35 12 05   Cyg X-1 = HD 226868
    -----------------------------------------------

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table1.dat       277     1819  *Results of fitting two Lorentzians and cut-off
                             power-law to power spectra of RXTE/PCA
                             observations of Cyg X-1 from 1996-2003.

Note on table1.dat:
    The frequency range is from 0.01Hz to 25Hz, with reanalyzed data
    (model Nb 3) extending to 50Hz. The energy range is 2-9keV.


See also:
   http://heasarc.gsfc.nasa.gov/FTP/xte/data/archive : XTE Archive


Byte-by-byte Description of file: table1.dat

   Bytes Format Units   Label     Explanations

   1- 15  A15   ---     ObsID     Proposal number and sub-ID
  17- 25  F9.3  d       Tstart    Start time in MJD
  27- 35  F9.3  d       Tstop     Stop time in MJD
      37  I1    ---     Model     [1/5] Model components presence (1)
  39- 49  E11.5 ct/s    F2-9keV   Average 2-9keV flux
  51- 61  E11.5 ---     HR        Average (9-20)keV/(2-4)keV flux ratio
  63- 73  E11.5 ---     A         Normalization of power-law (2)
  75- 85  E11.5 ---     e_A       Error of A
  87- 97  E11.5 ---     alpha     Index of power-law (2)
  99-109  E11.5 ---     e_alpha   Error of alpha
 111-121  E11.5 Hz      fc        Cut-off frequency for power-law (2)
 123-133  E11.5 Hz      e_fc      Error of fc
 135-145  E11.5 ---     W1        Width par of Lorentzian 1 (2)
 147-157  E11.5 ---     e_W1      Error of W1
 159-169  E11.5 Hz      H1        Height par of Lorentzian 1 (2)
 171-181  E11.5 Hz      e_H1      Error of H1
 183-193  E11.5 Hz      freq1     Peak frequency of Lorentzian 1 (2)
 195-205  E11.5 Hz      e_freq1   Error of freq1
 207-217  E11.5 ---     W2        Width par of Lorentzian 2 (2)
 219-229  E11.5 ---     e_W2      Error of W2
 231-241  E11.5 Hz      H2        Height par of Lorentzian 2 (2)
 243-253  E11.5 Hz      e_H2      Error of H2
 255-265  E11.5 Hz      freq2     Peak frequency of Lorentzian 2 (2)
 267-277  E11.5 Hz      e_freq2   Error of freq2

Note (1): Model components presence as follows:
      1 = only two Lorentzians are present,
      2 = two Lorentzians and cut-off power-law,
      3 = refitted results (two Lorentzians and cut-off power-law present),
      4 = first Lorentzian and cut-off power-law only,
      5 = purely cut-off power-law.
Note (2): We describe the power spectrum using a model of two Lorentzian
          components and a cut-off power-law.

      The Lorentzians have the form:
          L(f)=H*W*ν/((f-ν)2+f*W*ν), where
      H is the value of frequency times power at the peak frequency ν,
      and W a dimensionless measure of the relative width of the profile
      in the frequency times power (Pf) representation.

      The cut-off power-law is of the form:
          Pl(f)=A*f-α*e-(f/fc_)^ , where
      A is the normalization constant, α is the exponent, and
      fc is the turnover frequency.


Acknowledgements:
    Magnus Axelsson, magnusa(at)astro.su.se
    Luis Borgonovo, luis(at)astro.su.se
    Stefan Larsson, stefan(at)astro.su.se
(End) M. Axelsson, L. Borgonovo, S. Larsson [Stockholm Univ.]        31-Mar-2006