Periodic photometric variability of the black hole binary V404 Cygni

Wagner, R. M.; Kreidl, T. J.; Howell, Steve B.; Starrfield, S.

doi:10.1086/186680

Cited by 57 publications

(44 citation statements)

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“…Intensive photometric and spectroscopic follow-up of this historical event yielded an orbital period of about 6.5 d and remarkably concluded with the presence of a massive stellar black hole in the system (Casares et al 1992;Wagner et al 1992). The companion star of V404 Cygni has been proposed to be an object of a late-type K0(±1) III-V spectral type (Casares et al 1993).…”

Section: Introductionmentioning

confidence: 92%

Multi-colour optical photometry of V404 Cygni in outburst

Martı́

Luque-Escamilla

García-Hernández

2016

A&A

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Context. This observational paper has been prepared in the context of the large multi-wavelength effort by many observers with the aim of following up the transient flaring event of V404 Cygni that took place for several weeks in 2015 June. Aims. Our main original aim was to contribute to the study of this transient source by acquiring broad-band photometric observations during its most active flaring phases. Nevertheless, after a detailed analysis of the data, several interesting results were obtained that encouraged a dedicated publication. Methods. The methodology used was based on broad-band differential CCD photometry. This outburst of V404 Cygni rendered the source a very bright target easily within reach of small educational telescopes. Therefore, the 41 cm telescope available at the Astronomical Observatory of the University of Jaén was used in this work. Results. We detected variability at different time scales, both in amplitude and colour. Individual optical flares appear every half hour on average during our 3 h long observation, although large-amplitude (∼1 mag) variations are also observed to occur on intervals as short as 10 min. Also, colour variations appear to be highly correlated in a colour-colour diagram. Another remarkable finding is the detection of time lag, from about one to a fraction of a minute between light curves in different filters (VR c I c ).Conclusions. The observed behaviour is tentatively interpreted in an scenario based on the ejection of non-thermal emitting, relativistic plasmons, with their synchrotron spectra extending up to optical wavelengths. This would render some of the V404 Cygni flares very similar to those of the well-know microquasar GRS 1915+105

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Section: Introductionmentioning

confidence: 92%

Multi-colour optical photometry of V404 Cygni in outburst

Martı́

Luque-Escamilla

García-Hernández

2016

A&A

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“…In Figure 1 we show a sample of the observed light curves and the lower envelope constructed in this way, and in Figure 2 we present the detrended light curves in relative intensity units (see x 5). Furthermore, in order to compare the results of different References.-(1) Wagner et al 1992. (2) Shahbaz et al 1994b.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…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. To study whether this property is a peculiarity of this system or a common feature of the SXTs, we have embarked on a campaign of fast photometry of quiescent SXTs.…”

Section: Introductionmentioning

confidence: 99%

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Zurita

Casares

Shahbaz

2003

ApJ

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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“…During the outburst, the visual magnitude of V404 Cyg increased from V = 18.3 to V = 11.6. One year after its discovery, it had fallen back to V = 18.0 (Wagner et al 1992). Since then, V404 Cyg has been studied in quiescence at optical and infrared wavelengths, establishing most of the system parameters.…”

Section: Introductionmentioning

confidence: 99%

NEAR-INFRARED SPECTROSCOPY OF LOW-MASS X-RAY BINARIES: ACCRETION DISK CONTAMINATION AND COMPACT OBJECT MASS DETERMINATION IN V404 Cyg AND Cen X-4

Khargharia

Froning

Robinson

2010

ApJ

139

127

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We present near-infrared (NIR) broadband (0.80-2.42 μm) spectroscopy of two low-mass X-ray binaries: V404 Cyg and Cen X-4. One important parameter required in the determination of the mass of the compact objects in these systems is the binary inclination. We can determine the inclination by modeling the ellipsoidal modulations of the Roche-lobe filling donor star, but the contamination of the donor star light from other components of the binary, particularly the accretion disk, must be taken into account. To this end, we determined the donor star contribution to the infrared flux by comparing the spectra of V404 Cyg and Cen X-4 to those of various field K-stars of known spectral type. For V404 Cyg, we determined that the donor star has a spectral type of K3 III. We determined the fractional donor contribution to the NIR flux in the H and K bands as 0.98 ± 0.05 and 0.97 ± 0.09, respectively. We remodeled the H-band light curve from Sanwal et al. after correcting for the donor star contribution to obtain a new value for the binary inclination. From this, we determined the mass of the black hole in V404 Cyg to be M BH = 9.0 +0.2 −0.6 M . We performed the same spectral analysis for Cen X-4 and found the spectral type of the donor star to be in the range K5-M1 V. The donor star contribution in Cen X-4 is 0.94 ± 0.14 in the H band while in the K band, the accretion disk can contribute up to 10% of the infrared flux. We remodeled the H-band light curve from Shahbaz et al., again correcting for the fractional contribution of the donor star to obtain the inclination. From this, we determined the mass of the neutron star as M NS = 1.5 +0.1 −0.4 M . However, the masses obtained for both systems should be viewed with some caution since contemporaneous light curve and spectral data are required to obtain definitive masses.

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Periodic photometric variability of the black hole binary V404 Cygni

Cited by 57 publications

References 0 publications

Multi-colour optical photometry of V404 Cygni in outburst

Multi-colour optical photometry of V404 Cygni in outburst

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

NEAR-INFRARED SPECTROSCOPY OF LOW-MASS X-RAY BINARIES: ACCRETION DISK CONTAMINATION AND COMPACT OBJECT MASS DETERMINATION IN V404 Cyg AND Cen X-4

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