Swift J1357.2−0933: the faintest black hole?

Padilla, M. Armas; Wijnands, Rudy; Degenaar, N.; Muñoz-Darias, T.; Casares, J.; Fender, R. P.

doi:10.1093/mnras/stu1487

Cited by 41 publications

(45 citation statements)

References 36 publications

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“…Indeed, when we refit the quiescent Chandra X-ray spectrum allowing NH to vary as a free parameter, NH converges toward zero and the bestfit photon index remains similar (Γ = 2.6 +1.2 −0.8 ). This photon index is consistent with an XMM-Newton observation in quiescence taken by Armas Padilla et al (2014b) (λ2600) u (λ3465) Figure 2. The UV/X-ray luminosity correlation for J1357.2.…”

Section: X-ray Spectrumsupporting

confidence: 90%

“…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. Our other optical LT and UVOT u flux measurements are also brighter by a similar factor.…”

Section: Flux Variabilitysupporting

confidence: 63%

“…We perform the spectral fitting within ISIS, using Cash statistics (Cash 1979) with the background included in the fit (an energy-dependent aperture correction was applied to account for the finite size of the extraction region). We initially fixed the column density to the Galactic value of NH = 1.2 × 10 20 cm −2 (Krimm, Kennea & Holland 2011;Armas Padilla et al 2014b), and we found a bestfit photon index Γ = 2.6 ± 0.9. Armas Padilla et al (2014a) found negligible X-ray absorption for J1357.2 from a high-count XMM-Newton X-ray spectrum taken during its 2011 outburst.…”

Section: X-ray Spectrummentioning

confidence: 99%

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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: X-ray Spectrumsupporting

confidence: 90%

Section: Flux Variabilitysupporting

confidence: 63%

Section: X-ray Spectrummentioning

confidence: 99%

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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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“…Emission lines from the accretion disc have been detected in quiescence (Torres et al 2015;Mata Sánchez et al 2015), but its contribution to the continuum is likely to be low, since the UV flux is much fainter than the optical flux (Plotkin et al 2016). The X-ray luminosity is also very low, possibly the lowest measured of all black hole LMXBs (Armas Padilla et al 2014). The polarization of 8.0±2.5 per cent implies the magnetic field in the region of the jet near its base is moderately tangled.…”

Section: Swift J13572-0933mentioning

confidence: 94%

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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“…A similar conclusion was also reached for A0620-00 in quiescence, for which the same jet model converged toward similar best-fit parameters as we find for J1118 (Gallo et al 2007). Furthermore, the BHXB Swift J1357.2-0933 was recently suggested to have the lowest quiescent X-ray luminosity of any known BHXB (Armas Padilla et al 2014), making it suitable for comparisons to J1118 and A0620-00. Swift J1357.2-0933 has a very steep NIR-optical spectrum (αν = −1.4) in quiescence, which is also consistent with synchrotron radiation from a thermal distribution of electrons in a weak jet (Shahbaz et al 2013).…”

Section: Jets In Quiescencementioning

confidence: 99%

Constraints on relativistic jets in quiescent black hole X-ray binaries from broad-band spectral modelling

Plotkin

Gallo

Markoff

et al. 2014

Monthly Notices of the Royal Astronomical Society

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The nature of black hole jets at the lowest detectable luminosities remains an open question, largely due to a dearth of observational constraints. Here, we present a new, nearly-simultaneous broadband spectrum of the black hole X-ray binary (BHXB) XTE J1118+480 at an extremely low Eddington ratio (L X ∼ 10 −8.5 L Edd ). Our new spectral energy distribution (SED) includes the radio, near-infrared, optical, ultraviolet, and X-ray wavebands. XTE J1118+480 is now the second BHXB at such a low Eddington ratio with a well-sampled SED, thereby providing new constraints on highly sub-Eddington accretion flows and jets, and opening the door to begin comparison studies between systems. We apply a multi-zone jet model to the new broadband SED, and we compare our results to previous fits to the same source using the same model at 4-5 decades higher luminosity. We find that after a BHXB transitions to the so-called quiescent spectral state, the jet base becomes more compact (by up to an order of magnitude) and slightly cooler (by at least a factor of two). Our preferred model fit indicates that jet particle acceleration is much weaker after the transition into quiescence. That is, accelerated non-thermal particles no longer reach high enough Lorentz factors to contribute significant amounts of synchrotron X-ray emission. Instead, the X-ray waveband is dominated by synchrotron self-Compton emission from a population of mildly relativistic electrons with a quasi-thermal velocity distribution that are associated with the jet base. The corresponding (thermal) synchrotron component from the jet base emits primarily in the infrared through ultraviolet wavebands. Our results on XTE J1118+480 are consistent with broadband modeling for A0620-00 (the only other comparably low Eddington ratio BHXB with a well-sampled SED) and for Sgr A* (the quiescent supermassive black hole at the Galactic center). The above could therefore represent a canonical baseline geometry for accreting black holes in quiescence. We conclude with suggestions for future studies to further investigate the above scenario.

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Swift J1357.2−0933: the faintest black hole?

Cited by 41 publications

References 36 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

Polarized synchrotron emission in quiescent black hole X-ray transients

Constraints on relativistic jets in quiescent black hole X-ray binaries from broad-band spectral modelling

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