Characterizing the quiescent X-ray variability of the black hole low-mass X-ray binary V404 Cyg
Abstract
We conducted the first long-term (75 d) X-ray monitoring of the black hole low-mass X-ray binary V404 Cyg, with the goal of understanding and characterizing its variability during quiescence. The X-ray light curve of V404 Cyg shows several flares on time-scales of hours with a count rate change of a factor of about 5-8. The root-mean-square variability is Fvar = 57.0 ± 3.2 per cent. The first-order structure function is consistent with both a power spectrum of index -1 (flicker noise), or with a power spectrum of index 0 (white noise), implying that the light curve is variable on time-scales from days to months. The X-ray spectrum is well fitted by a power law with spectral index Γ = 2.10-2.35, and we found that the spectral shape remains roughly constant as the flux changes. A constant spectral shape with respect to a change in the X-ray flux may favour a scenario in which the X-ray emission is dominated by synchrotron radiation produced in a jet.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2014
- DOI:
- 10.1093/mnras/stu140
- arXiv:
- arXiv:1401.4113
- Bibcode:
- 2014MNRAS.439.2771B
- Keywords:
-
- accretion;
- accretion discs;
- black hole physics;
- stars: black holes;
- X-rays: binaries;
- X-rays: individual: V404 Cyg;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 11 pages, 7 figures, 2 tables, accepted on MNARS on January 16 2014