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

Hynes, R. I.; Charles, P. A.; Garcia, M. R.; Robinson, E. L.; Casares, J.; Haswell, C. A.; Kong, Albert; Rupen, M.; Fender, R. P.; Wagner, R. M.; Gallo, Elena; Eves, B.A.C.; Shahbaz, T.; Zurita, C.

doi:10.1086/424005

Cited by 67 publications

(98 citation statements)

References 31 publications

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“…The Chandra X-ray flux is almost a factor of three brighter than the quiescent flux from an XMM-Newton observation obtained nine months earlier (Armas Padilla et al 2014b find fX = 3.2 × 10 −15 erg s −1 cm −2 , compared to fX = 8.2 × 10 −15 erg s −1 cm −2 from Chandra). This level of Xray variability is typical for quiescent BHXB systems (e.g., Hynes et al 2004;Bernardini & Cackett 2014). On the same day as the XMM-Newton observation, a fainter optical flux of r ′ = 22.29 ± 0.08 mag (omitted from Figure 4 for clarity) was observed with the LT (Armas Padilla et al 2014b); our 2014 r ′ flux measurement is 4-5 times brighter.…”

Section: Flux Variabilitysupporting

confidence: 65%

A clean sightline to quiescence: multiwavelength observations of the high Galactic latitude black hole X-ray binary Swift J1357.2−0933

Plotkin

Gallo

Jonker

et al. 2015

Mon. Not. R. Astron. Soc.

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We present coordinated multiwavelength observations of the high Galactic latitude (b=+50 • ) black hole X-ray binary (BHXB) Swift J1357.2−0933 in quiescence. Our broadband spectrum includes strictly simultaneous radio and X-ray observations, and near-infrared, optical, and ultraviolet data taken 1-2 days later. We detect Swift J1357.2−0933 at all wavebands except for the radio (f 5GHz <3.9 µJy beam −1 ; 3σ rms ). Given current constraints on the distance (2.3-6.3 kpc), its 0.5-10 keV X-ray flux corresponds to an Eddington ratio L X /L Edd = 4 × 10 −9 − 3 × 10 −8 (assuming a black hole mass of 10M ⊙ ). The broadband spectrum is dominated by synchrotron radiation from a relativistic population of outflowing thermal electrons, which we argue to be a common signature of short-period quiescent BHXBs. Furthermore, we identify the frequency where the synchrotron radiation transitions from optically thick-to-thin (ν b ≈ 2 − 5 × 10 14 Hz, which is the most robust determination of a 'jet break' for a quiescent BHXB to date. Our interpretation relies on the presence of steep curvature in the ultraviolet spectrum, a frequency window made observable by the low amount of interstellar absorption along the line of sight. High Galactic latitude systems like Swift J1357.2−0933 with clean ultraviolet sightlines are crucial for understanding black hole accretion at low luminosities.

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Section: Flux Variabilitysupporting

confidence: 65%

A clean sightline to quiescence: multiwavelength observations of the high Galactic latitude black hole X-ray binary Swift J1357.2−0933

Plotkin

Gallo

Jonker

et al. 2015

Mon. Not. R. Astron. Soc.

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“…It is worth noting though that distance uncertainties can not be modelled as uncorrelated errors, as they have the effect of shifting data points for a specific system along the LX∝Lr plane, rather than randomizing the measurements. All considered, 0.3 dex, or a factor ∼2 in luminosity seems to be a fair representation of the observed short-term radio and X-ray luminosity variability for hard and quiescent state black hole X-ray binaries (Garcia et al 2001;Gallo et al 2006;Gallo et al 2007;Hynes et al 2003aHynes et al , 2004Hynes et al , 2006Hynes et al , 2009Bradley et al 2007;Miller-Jones et al 2008;Bernardini & Cackett 2014; notice that σ 0.15 dex was adopted in previous works, e.g. Corbel et al 2013), and it also accounts for the uncertainties in the slope of the partially self-absorbed radio jet (often assumed as flat; please see § 5 for a quantitative discussion).…”

Section: Xte J1118+480 In the Radio/x-ray Domainmentioning

confidence: 83%

The radio/X-ray domain of black hole X-ray binaries at the lowest radio luminosities

Gallo¹,

Miller-Jones²,

Russell³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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154

200

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We report on deep, coordinated radio and X-ray observations of the black hole X-ray binary XTE J1118+480 in quiescence. The source was observed with the Karl G. Jansky Very Large Array for a total of 17.5 hrs at 5.3 GHz, yielding a 4.8±1.4 µJy radio source at a position consistent with the binary system. At a distance of 1.7 kpc, this corresponds to an integrated radio luminosity between 4-8 ×10 25 erg s −1 , depending on the spectral index. This is the lowest radio luminosity measured for any accreting black hole to date. Simultaneous observations with the Chandra X-ray Telescope detected XTE J1118+480 at 1.2 × 10 −14 erg s −1 cm −2 (1-10 keV), corresponding to an Eddington ratio of ∼4 × 10 −9 for a 7.5 M black hole. Combining these new measurements with data from the 2005 and 2000 outbursts available in the literature, we find evidence for a relationship of the form r =α+β X (where denotes logarithmic luminosities), with β = 0.72 ± 0.09. XTE J1118+480 is thus the third system -together with GX339-4 and V404 Cyg -for which a tight, non-linear radio/X-ray correlation has been reported over more than 5 dex in X . Confirming previous results, we find no evidence for a dependence of the correlation normalisation of an individual system on orbital parameters, relativistic boosting, reported black hole spin and/or black hole mass. We then perform a clustering and linear regression analysis on what is arguably the most up-to-date collection of coordinated radio and X-ray luminosity measurements from quiescent and hard state black hole X-ray binaries, including 24 systems. At variance with previous results, a two-cluster description is statistically preferred only for random errors < ∼ 0.3 dex in both r and X , a level which we argue can be easily reached when the known spectral shape/distance uncertainties and intrinsic variability are accounted for. A linear regression analysis performed on the whole data set returns a best-fitting slope β = 0.61 ± 0.03 and intrinsic scatter σ 0 = 0.31 ± 0.03 dex.

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“…For A0620À00, we make use of new optical data, presented in x 3.3.1. Clearly, the nonstrict simultaneity of the observations, combined with the known variability of quiescent BHBs at all wavelengths (e.g., Hynes et al 2003Hynes et al , 2004, should be kept in mind before drawing any definitive conclusion on the modeling. Figure 2 shows the broadband SEDs of V404 Cyg, XTE J1118+480, and A0620À00 while in the quiescent state, from radio to optical wavelengths.…”

Section: Radio/infrared/optical Spectramentioning

confidence: 99%

“…V404 Cyg (GS 2023+338) Casares et al (1993) report on B-, V-, R-, J-, H-, and K-band photometry of V404 Cyg taken from 1991 July to August, 2 years after the end of the 1989 outburst that preceded the current quiescent regime (even though this system, because of its relatively high quiescent X-ray luminosity [L X /L Edd ' 10 À6:5 ], is often considered at the boundary between quiescence and the hard X-ray state). Several later works have established V404 Cyg to be variable by a factor of a few at IR-to-X-ray wavelengths (see, e.g., Hynes et al 2004, Bradley et al 2007 for the X-ray/optical variability; Zurita et al 2004 and references therein for a study of the long term optical/IR variability). The origin of such variability is yet to be well understood, even though there is general Table 2 for the fitted parameters); curves in the middle panels are for a double-blackbody fit (Table 3); the right panels show the fit to the radio/ IR /optical SEDs with a single-blackbody, plus a broken power law ( Table 4).…”

Section: Radio/infrared/optical Spectramentioning

confidence: 99%

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

Cited by 67 publications

References 31 publications

A clean sightline to quiescence: multiwavelength observations of the high Galactic latitude black hole X-ray binary Swift J1357.2−0933

A clean sightline to quiescence: multiwavelength observations of the high Galactic latitude black hole X-ray binary Swift J1357.2−0933

The radio/X-ray domain of black hole X-ray binaries at the lowest radio luminosities

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

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