Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Zurita, C.; Casares, J.; Shahbaz, T.

doi:10.1086/344534

Cited by 85 publications

(132 citation statements)

References 44 publications

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“…Single Blackbody Fits to the IR /Optical Spectra agreement that it should take place somewhere in the accretion flow rather than in the hot gas stream/donor star Zurita et al 2003;Hynes et al 2003Hynes et al , 2004.…”

Section: Tablementioning

confidence: 90%

The Spectral Energy Distribution of Quiescent Black Hole X‐Ray Binaries: New Constraints fromSpitzer

Gallo¹,

Migliari²,

Markoff³

et al. 2007

ApJ

108

174

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Among the various issues that remain open in the field of accretion onto black hole X-ray binaries (BHBs) is the question of how gas accretes at very low Eddington ratios, in the so-called quiescent regime. While there is general agreement that X-rays are produced by a population of high-energy electrons near the BH, there is controversy concerning the modeling of the contributions of inflowing versus outflowing particles and their relative energy budget. Recent Spitzer observations of three quiescent BHBs have shown evidence for excess emission with respect to the Rayleigh-Jeans tail of the companion star between 8Y24 m. We suggest that synchrotron emission from a partially self-absorbed outflow might be responsible for the observed mid-IR excess, in place of, or in addition to, thermal emission from circumbinary material. If so, then the jet synchrotron luminosity, integrated from radio to near-IR frequencies, exceeds the measured 2Y10 keV luminosity by a factor of a few in these systems. In turn, the mechanical power stored in the jet exceeds the bolometric X-ray luminosity by at least 4 orders of magnitude. We compile the broadband spectral energy distribution (SED) of A0620À00, the lowest Eddington-ratio stellar mass BH with a known radio counterpart, by means of simultaneous radio, optical, and X-ray observations, and the archival Spitzer data. We are able to fit the SED of A0620À00 with a maximally jet-dominated model, in which the radio through the soft X-rays are dominated by synchrotron emission, while the hard X-rays are dominated by inverse Compton at the jet base. The fitted parameters land in a range of values reminiscent of the Galactic center supermassive black hole Sgr A Ã . Most notably, the inferred ratio of the jet acceleration rate to local cooling rates is 2 orders of magnitude weaker than higher luminosity, hard-state sources.

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Section: Tablementioning

confidence: 90%

The Spectral Energy Distribution of Quiescent Black Hole X‐Ray Binaries: New Constraints fromSpitzer

Gallo¹,

Migliari²,

Markoff³

et al. 2007

ApJ

108

174

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“…Rutledge et al 2001;Degenaar & Wijnands 2012;Bernardini & Cackett 2014;Coti Zelati et al 2014) and the UV/optical/infrared properties (e.g. Orosz et al 1994;Zurita et al 2003;Shahbaz et al 2005;Cantrell et al 2008;Yang et al 2012;MacDonald et al 2014;Bernardini et al 2016;Koljonen et al 2016) in quiescence can be explained by a truncated disc and a radiatively inefficient accretion flow. The X-ray and optical fluxes can be positively correc 2016 The Authors lated on long (e.g.…”

Section: Introductionmentioning

confidence: 99%

Polarized synchrotron emission in quiescent black hole X-ray transients

Russell¹,

Shahbaz²,

Lewis³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present near-infrared polarimetric observations of the black hole X-ray binaries Swift J1357.2-0933 and A0620-00. In both sources, recent studies have demonstrated the presence of variable infrared synchrotron emission in quiescence, most likely from weak compact jets. For Swift J1357.2-0933 we find that the synchrotron emission is polarized at a level of 8.0 ± 2.5 per cent (a 3.2 σ detection of intrinsic polarization). The mean magnitude and rms variability of the flux (fractional rms of 19-24 per cent in K S -band) agree with previous observations. These properties imply a continuously launched (stable on long timescales), highly variable (on short timescales) jet in the Swift J1357.2-0933 system in quiescence, which has a moderately tangled magnetic field close to the base of the jet. We find that for A0620-00, there are likely to be three components to the optical-infrared polarization; interstellar dust along the line of sight, scattering within the system, and an additional source that changes the polarization position angle in the reddest (H and K S ) wave-bands. We interpret this as a stronger contribution of synchrotron emission, and by subtracting the line-of-sight polarization, we measure an excess of ∼ 1.25±0.28 per cent polarization and a position angle of the magnetic field vector that is consistent with being parallel with the axis of the resolved radio jet. These results imply that weak jets in low luminosity accreting systems have magnetic fields which possess similarly tangled fields compared to the more luminous, hard state jets in X-ray binaries.

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“…Mass transfer instabilities, magnetic reconnection events, and X-ray reprocessing in the accretion disc (Hynes et al 2002;Zurita et al 2003) might in principle also explain a strong flaring activity in LMXBs. No enhanced X-ray activity has been detected in IGR J00291+5934 near the epoch of our observations in 2014.…”

Section: Discussionmentioning

confidence: 99%

“…Magnetic reconnection events in the disc could also trigger the flares (Hynes et al 2002;Zurita et al 2003). In particular, differential motions in the accretion disc plasma may produce magnetic fields, and when the reconnection between vertical field lines of opposite signs occurs, some energy is dissipated, leading to the emission of flares.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, differential motions in the accretion disc plasma may produce magnetic fields, and when the reconnection between vertical field lines of opposite signs occurs, some energy is dissipated, leading to the emission of flares. In this scenario, the duration of flares must then be related to the timescale of shearing in the accretion disc, and should be more efficient in the outer regions of the disc, where the amount of shearing is higher (see Zurita et al 2003). If we assume that the duration of flares is linked to their location in the accretion disc, flares with the longest duration should then be the most significant.…”

Section: Discussionmentioning

confidence: 99%

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The puzzling case of the accreting millisecond X-ray pulsar IGR J00291+5934: flaring optical emission during quiescence

Baglio

Campana

D’Avanzo

et al. 2017

A&A

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We present an optical (gri) study during quiescence of the accreting millisecond X-ray pulsar IGR J00291+5934 performed with the 10.4m Gran Telescopio Canarias (GTC) in August 2014. Although the source was in quiescence at the time of our observations, it showed a strong optical flaring activity, more pronounced at higher frequencies (i.e. the g band). After subtracting the flares, we tentatively recovered a sinusoidal modulation at the system orbital period in all bands, even when a significant phase shift with respect to an irradiated star, typical of accreting millisecond X-ray pulsars, was detected. We conclude that the observed flaring could be a manifestation of the presence of an accretion disc in the system. The observed light curve variability could be explained by the presence of a superhump, which might be another proof of the formation of an accretion disc. In particular, the disc at the time of our observations was probably preparing the new outburst of the source, which occurred a few months later, in 2015.

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Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Cited by 85 publications

References 44 publications

The Spectral Energy Distribution of Quiescent Black Hole X‐Ray Binaries: New Constraints fromSpitzer

The Spectral Energy Distribution of Quiescent Black Hole X‐Ray Binaries: New Constraints fromSpitzer

Polarized synchrotron emission in quiescent black hole X-ray transients

The puzzling case of the accreting millisecond X-ray pulsar IGR J00291+5934: flaring optical emission during quiescence

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