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Register a new userThe Curious Case of Swift J1753.5-0127: A Black Hole Low-mass X-ray Binary Analogue to Z Cam Type Dwarf Novae
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Swift J1753.5-0127 (J1753) is a candidate black hole low-mass X-ray binary (BH-LMXB) that was discovered in outburst in May 2005. It remained in outburst for $sim12$ years, exhibiting a wide range of variability on various timescales, before entering quiescence after two short-lived, low-luminosity mini-outbursts in April 2017. The unusually long outburst duration in such a short-period ($P_{rm orb}approx3.24$ hrs) source, and complex variability observed during this outburst period, challenges the predictions of the widely accepted disc-instability model, which has been shown to broadly reproduce the behaviour of LMXB systems well. The long-term behaviour observed in J1753 is reminiscent of the Z Cam class of dwarf novae, whereby variable mass transfer from the companion star drives unusual outbursts, characterized by stalled decays and abrupt changes in luminosity. Using sophisticated modelling of the multi-wavelength light curves and spectra of J1753, during the $sim12$ years the source was active, we investigate the hypothesis that periods of enhanced mass transfer from the companion star may have driven this unusually long outburst. Our modelling suggests that J1753 is in fact a BH-LMXB analogue to Z Cam systems, where the variable mass transfer from the companion star is driven by the changing irradiation properties of the system, affecting both the disc and companion star.
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We present high-resolution, time-resolved optical spectroscopy of the black hole X-ray transient Swift J1753.5-0127. Our optical spectra do not show features that we can associate with the companion star. However we do observe broad, double-peaked emission lines, typical of an accretion disc. We show that the mass of the compact object is likely $>7.4pm1.2M_{odot}$, much higher than previous suggestions of a low-mass ($<5M_{odot}$) black hole.
We present a spectral analysis of the black hole candidate and X-ray transient source Swift J1753.5 0127 making use of simultaneous observations of XMM-Newton and Rossi X-ray Timing Explorer (RXTE) in 2006, when the source was in outburst. The aim of this paper is to test whether a thermal component due to the accretion disc is present in the X-ray spectrum. We fit the data with a range of spectral models, and we find that for all of these models the fits to the X-ray energy spectra significantly require the addition of the disc black-body component. We also find a broad iron emission line at around 6.5 keV, most likely due to iron in the accretion disc. Our results confirm the existence of a cool inner disc extending near or close to the innermost circular orbit (ISCO).We further discovered broad emission lines of NVII and OVIII at ~ 0.52 keV and 0.65 keV, respectively in the RGS spectrum of Swift J1753.5-0127.
(abridged) We report on multi-wavelength measurements of Swift J1753.5-0127 in the hard state at L=2.7e36 erg/s (assuming d=3 kpc) in 2014. The radio emission is optically thick synchrotron, presumably from a compact jet. We take advantage of the low extinction and model the near-IR to UV emission with a multi-temperature disk model. Assuming a BH mass of M_BH=5 Msun and a system inclination of 40 deg, the fits imply an inner radius for the disk of Rin/Rg>212 d_3 (5Msun/M_BH). The outer radius is R_out/R_g=90,000 d_3 (5Msun/M_BH), which corresponds to 6.6e10 d_3 cm, consistent with the expected size of the disk. The 0.5-240 keV spectrum measured by Swift/XRT, Suzaku, and NuSTAR is relatively well characterized by a power-law with a photon index of Gamma=1.722+/-0.003, but a significant improvement is seen when a second continuum component is added. Reflection is a possibility, but no iron line is detected, implying a low iron abundance. We are able to fit the entire SED with a multi-temperature disk component, a Comptonization component, and a broken power-law, representing the emission from the compact jet. The broken power-law cannot significantly contribute to the soft X-ray emission, and this may be related to why Swift J1753.5-0127 is an outlier in the radio/X-ray correlation. The broken power-law might dominate above 20 keV, which would constrain the break frequency to be between 2.4e10 Hz and 3.6e12 Hz. Although the fits to the full SED do not include significant thermal emission in the X-ray band, previous observations have consistently seen such a component, and we find that there is evidence at the 3.1-sigma level for a disk-blackbody component with a temperature of 150(+30)(-20) eV and an inner radius of 5-14 R_g. If this component is real, it might imply the presence of an inner accretion disk in addition to the strongly truncated (R_in>212 R_g) disk.
We report the discovery of the correlated optical/X-ray low-frequency quasi-periodic oscillations (QPOs) in black hole binary SWIFT J1753.5-0127. The phase lag between two light-curves at the QPO frequency is close to zero. This result puts strong constraints on the nature of the optical emission in this object and on the origin of the QPOs in general. We demonstrate that the QPO signal and the broadband variability can be explained in terms of the hot accretion flow radiating in both optical and X-ray bands. In this model, the QPO appears due to the Lense-Thirring precession of entire flow, while the broadband variability in the optical is produced by two components: the hot flow and the irradiated disc. Using the phase-lag spectra, we put a lower limit on the orbital inclination i>50 deg, which can be used to constrain the mass of the compact object.
We report on radio and X-ray monitoring observations of the BHC Swift J1753.5-0127 taken over a ~10 year period. Presented are daily radio observations at 15 GHz with the AMI-LA and X-ray data from Swift XRT and BAT. Also presented is a deep 2hr JVLA observation taken in an unusually low-luminosity soft-state (with a low disk temperature). We show that although the source has remained relatively radio-quiet compared to XRBs with a similar X-ray luminosity in the hard-state, the power-law relationship scales as $zeta=0.96pm0.06$ i.e. slightly closer to what has been considered for radiatively inefficient accretion disks. We also place the most stringent limit to date on the radio-jet quenching in an XRB soft-state, showing the connection of the jet quenching to the X-ray power-law component; the radio flux in the soft-state was found to be $<21~mu$Jy, which is a quenching factor of $gtrsim25$
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