<i>Kepler</i>K2 observations of Sco X-1: orbital modulations and correlations with<i>Fermi</i>GBM and MAXI

Hynes, R. I.; Schaefer, Bradley E.; Baum, Zachary A.; Hsu, C. C.; Cherry, M. L.; Scaringi, Simone

doi:10.1093/mnras/stw854

Cited by 13 publications

(9 citation statements)

References 60 publications

(108 reference statements)

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“…In this scenario, light travel-time delays between the X-rays and the optical emission are expected. Such time lags have been observed for instance in Sco X-1 (Muñoz-Darias et al 2007;Hynes et al 2016). However, other mechanisms (e.g.…”

Section: Introductionmentioning

confidence: 59%

Optical/X-ray correlations during the V404 Cygni June 2015 outburst

Alfonso-Garzón

Sánchez–Fernández

Charles

et al. 2018

A&A

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Context. We present a multiwavelength analysis of the simultaneous optical and X-ray light curves of the microquasar V404 Cyg during the June 2015 outburst. Aims. We have performed a comprehensive analysis of all the INTEGRAL/IBIS, JEM–X, and OMC observations during the brightest epoch of the outburst, along with complementary NuSTAR, AAVSO, and VSNET data, to examine the timing relationship between the simultaneous optical and X-ray light curves, in order to understand the emission mechanisms and physical locations. Methods. We have identified all optical flares that have simultaneous X-ray observations, and performed a cross-correlation analysis to estimate the time delays between the optical and soft and hard X-ray emission. We also compared the evolution of the optical and X-ray emission with the hardness ratios. Results. We have identified several types of behaviour during the outburst. On many occasions, the optical flares occur simultaneously with X-ray flares, but at other times, positive and negative time delays between the optical and X-ray emission are measured. Conclusions. We conclude that the observed optical variability is driven by different physical mechanisms, including reprocessing of X-rays in the accretion disc and/or the companion star, interaction of the jet ejections with surrounding material or with previously ejected blobs, and synchrotron emission from the jet.

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Section: Introductionmentioning

confidence: 59%

Optical/X-ray correlations during the V404 Cygni June 2015 outburst

Alfonso-Garzón

Sánchez–Fernández

Charles

et al. 2018

A&A

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“…Such time lags have been observed e.g. in Sco X-1 (Muñoz-Darias et al 2007;Hynes et al 2016). However, there are other mechanisms (e.g.…”

Section: Introductionmentioning

confidence: 63%

Optical/X-ray correlations during the V404 Cyg June 2015 outburst

Alfonso-Garzón,

Sánchez-Fernández,

Charles

et al. 2018

Preprint

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Context. We present a multiwavelength analysis of the simultaneous optical and X-ray light curves of the microquasar V404 Cyg during the June 2015 outburst. Aims. We have performed a comprehensive analysis of all the INTEGRAL/IBIS, JEM-X, and OMC observations during the brightest epoch of the outburst, along with complementary NuSTAR, AAVSO, and VSNET data, to examine the timing relationship between the simultaneous optical and X-ray light curves, in order to understand the emission mechanisms and physical locations. Methods. We have identified all optical flares which have simultaneous X-ray observations, and performed cross-correlation analysis to estimate the time delays between the optical and soft and hard X-ray emission. We have also compared the evolution of the optical and X-ray emission with the hardness-ratios. Results. We have identified several types of behaviour during the outburst. On many occasions, the optical flares occur simultaneously with X-ray flares, but at other times positive and negative time delays between the optical and X-ray emission are measured. Conclusions. We conclude that the observed optical variability is driven by different physical mechanisms, including reprocessing of X-rays in the accretion disc and/or the companion star, interaction of the jet ejections with surrounding material or with previously ejected blobs, and synchrotron emission from the jet.

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“…Although no flickering plateaus appear in either light curve, there are some peaks in the optical light curve that correlate with X-ray peaks, such as the three peaks in the MJD region 54970.75-54970.76. In addition, Sco X-1 is solidly on the FB during these observations, the only place reprocessing has been seen in Sco X-1 (Hynes et al 2016 ). For these reasons, this peak is an extremely promising candidate for reprocessing.…”

Section: Data D E S C R I P T I O Nmentioning

confidence: 86%

Links between optical and X-ray light in Scorpius X-1

Igl,

Hynes,

Britt

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We observed the low-mass X-ray binary Sco X-1 for 12 nights simultaneously using the Rossi X-Ray Timing Explorer and the Otto Struve Telescope at McDonald Observatory at 1 second time resolution. This is among the most comprehensive simultaneous X-Ray/optical data sets of Sco X-1. Evidence of reprocessing was observed in the form of nine positive, near-zero lag peaks in the cross correlation function, eight of which were relatively small and took the shape of piecewise exponential functions. These peaks were initially identified by eye, after which a computational identification scheme was developed to confirm their significance. Based on their short lags (less than 4 seconds), as well as their occurrence on the flaring branch and soft apex, the small cross correlation features are likely to be caused by reprocessing off the outer disc, although the companion could still make a contribution to their tails. The Z track was parameterized using a rank number scheme so that the system’s location on the track could be numerically defined. Plotting the results against the optical reveals an increasing step function when moving from the horizontal to the normal to the flaring branch, with differential optical levels at ∼0.47, ∼0.57, and ∼1.1 respectively. An additional correlation between Z track location and the optical was found on the upper flaring branch. An optical intensity histogram reveals a transition region between the normal and flaring branches with only intermediate fluxes.

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KeplerK2 observations of Sco X-1: orbital modulations and correlations withFermiGBM and MAXI

Cited by 13 publications

References 60 publications

Optical/X-ray correlations during the V404 Cygni June 2015 outburst

Optical/X-ray correlations during the V404 Cygni June 2015 outburst

Optical/X-ray correlations during the V404 Cyg June 2015 outburst

Links between optical and X-ray light in Scorpius X-1

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