Orbital and quasi-periodic optical variations in the black hole X-ray binary V404 Cyg

Павленко, Е. П.; Martin, Angela C.; Casares, J.; Charles, P. A.; Ketsaris, N. A.

doi:10.1093/mnras/281.3.1094

Cited by 28 publications

(40 citation statements)

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“…For GS 2000+25 and V404 Cyg, the peaks detected in the periodograms of data from individual nights are not significant at the 99% level. Since there is evidence for a 6 hr periodicity in V404 Cyg (Pavlenko et al 1996 and reference therein), we compute a single periodogram using all the data and compare it with that obtained by Pavlenko et al (1996) from data taken in 1992. The significant peaks are only detected above 1 hr, but the periodogram shows a complicated one-dimensional alias pattern that makes it difficult to discern the 6 hr periodicity (see Fig.…”

Section: Searching For Periodicitiesmentioning

confidence: 99%

“…It is largely known that the highest mass black hole SXT, V404 Cyg, exhibits short-term quasi-periodic optical variability in quiescence, superposed on the ellipsoidal modulation (e.g., Pavlenko et al 1996). Although this variability has been observed since the onset of the quiescent phase (Wagner et al 1992;Casares et al 1993), its origin is still unknown.…”

Section: Introductionmentioning

confidence: 99%

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Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Zurita

Casares

Shahbaz

2003

ApJ

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120

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We present the results of high time resolution optical photometry of five quiescent soft X-ray transients (SXTs): V404 Cyg, A0620À00, J0422+32, GS 2000+25, and Cen X-4. We detect fast optical variations superposed on the secondary star's double-humped ellipsoidal modulation. The variability resembles typical flare activity and has amplitudes ranging from 0.06 to 0.6 mag. Flares occur on timescales of minutes to a few hours, with no dependency on orbital phase, and contribute $19%-46% to the total veiling observed in the R band. We find that the observed level of flaring activity is veiled by the light of the companion star, and therefore, systems with cool companions (e.g., J0422+32) exhibit stronger variability. After correcting for this dilution, we do not find any correlation between the flaring activity and fundamental system parameters. We find no underlying coherent periods in the data, only quasi-periodic variations ranging between 30 and 90 minutes for the short-period SXTs and longer than 1 hr for V404 Cyg. The power-law index of the power spectra is consistent with what is observed at X-rays wavelengths, i.e., a 1/f distribution, which is compatible with the cellular automaton model. Our observed R 0 -band luminosities, which are in the range 10 31 -10 33 ergs s À1 , are too large to be due to chromospheric activity in the rapidly rotating companions. Since the typical timescale of the flares increases with orbital period, they are most likely produced in the accretion disk. The associated dynamical (Keplerian) timescales suggest that flares are produced at $0.3R d -0.7R d . Possible formation mechanisms are magnetic loop reconnection events in the disk or, less likely, optical reprocessing of X-ray flares. In the former scenario, the maximum duration of the flares suggests that the outer disk is responsible for the flare events and so allows us to constrain the sharing timescale to $ 5 6 ð Þ À1 K .

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Section: Searching For Periodicitiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Zurita

Casares

Shahbaz

2003

ApJ

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120

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“…We assume a nonrotating black hole, so the model is parameterized by the inner and outer radius of the disk, and , respec-R R in out tively, and the radial distribution of irradiation emissivity. We fix the form of the emissivity, , as expected from We assume that the inclination of the system is ⅙ i ϭ 56 (Pavlenko et al 1996).…”

Section: Modelmentioning

confidence: 99%

Relativistically Smeared X-Ray Reprocessed Components in the [ITAL]Ginga[/ITAL] Spectra of GS 2023+338

Życki

Done

Smith

1997

The Astrophysical Journal

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We present results of spectral analysis of Ginga data obtained during the decline phase after the 1989 outburst of GS 2023ϩ338 (V404 Cyg). Our analysis includes detailed modeling of the effects of X-ray reflection/reprocessing. We have found that (1) the contribution of the reprocessed component (both continuum and line) corresponds to the solid angle of the reprocessor as seen from the X-ray source of Q ≈ (0.4-0.5) # 2p, and (2) the reprocessed component (both line and continuum) is broadened ("smeared") by kinematic and relativistic effects, as expected from the accretion disk reflection. We discuss the constraints these results give on various possible system geometries.

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“…Of the stellar mass black hole population, the most accessible quiescent object is V404 Cyg. V404 Cyg is known to vary in X-rays (Wagner et al 1994;Kong et al 2002), optical (Wagner et al 1992;Casares et al 1993;Pavlenko et al 1996;Hynes et al 2002;Zurita et al 2003;Shahbaz et al 2003), IR (Sanwal et al 1996), and radio (Hjellming et al 2000), but none of these studies were coordinated. Hynes et al (2002) established that optical emission line variations are correlated with the optical continuum.…”

Section: Introductionmentioning

confidence: 99%

Correlated X-Ray and Optical Variability in V404 Cygni in Quiescence

Hynes

Charles

Garcia

et al. 2004

ApJ

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We report simultaneous X-ray and optical observations of V404 Cyg in quiescence. The X-ray flux varied dramatically by a factor of տ20 during a 60 ks observation. X-ray variations were well correlated with those in Ha, although the latter include an approximately constant component as well. Correlations can also be seen with the optical continuum, although these are less clear. We see no large lag between X-ray and optical line variations; this implies they are causally connected on short timescales. As in previous observations, Ha flares exhibit a double-peaked profile suggesting emission distributed across the accretion disk. The peak separation is consistent with material extending outward to at least the circularization radius. The prompt response in the entire Ha line confirms that the variability is powered by X-ray (and/or EUV) irradiation.

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Orbital and quasi-periodic optical variations in the black hole X-ray binary V404 Cyg

Cited by 28 publications

References 0 publications

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Relativistically Smeared X-Ray Reprocessed Components in the [ITAL]Ginga[/ITAL] Spectra of GS 2023+338

Correlated X-Ray and Optical Variability in V404 Cygni in Quiescence

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