Repeated short-term spectral softening in the low/hard state of the Galactic black hole candidate Swift J1753.5−0127

Yoshikawa, A.; Yamada, S.; Nakahira, S.; Matsuoka, M.; Negoro, H.; Mihara, T.; Tamagawa, Toru

doi:10.1093/pasj/psu140

Cited by 14 publications

(22 citation statements)

References 22 publications

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“…There appeared to be two so-called "failed statetransitions" (Soleri et al 2013;Yoshikawa et al 2015) that occurred around MJD 55400 and 56000 that showed the source to increase in soft flux but no significant increase was seen at harder bands. Unfortunately no radio observations were available during those epochs.…”

Section: Results and Analysismentioning

confidence: 99%

“…The source has still not re-turned to quiescence, ∼ 10 years after its initial discovery, and has instead exhibited significant long-term (> 400 day) variability over the course of its prolonged 'outburst' (Shaw et al 2013). Swift J1753.5 has remained as a persistent LMXB in a hard accretion state for the majority of this time, however it has experienced a number of short-term spectral softenings, characterised by an increase in the temperature of the inner accretion disk and simultaneous steepening of the power law component in the X-ray spectrum (Yoshikawa et al 2015). Investigation of the source during one such event with RXTE revealed that it had transitioned to a hard intermediate accretion state.…”

Section: Introductionmentioning

confidence: 99%

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Disc–jet quenching of the galactic black hole Swift J1753.5−0127

Rushton¹,

Shaw²,

Fender³

et al. 2016

Mon. Not. R. Astron. Soc.

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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 ζ = 0.96 ± 0.06 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 µJy, which is a quenching factor of 25.

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Section: Results and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Disc–jet quenching of the galactic black hole Swift J1753.5−0127

Rushton¹,

Shaw²,

Fender³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Separately, we also find that the rms variability has decreased significantly (Uttley et al, in prep) and a sudden drop in the radio flux (Rushton, private communication), suggesting that the compact jet has switched off -also evidence of a transition to a disk-dominated soft state. The HID constructed from ∼10 years of Swift-XRT observations shows that the source has indeed reached its softest state ever observed, with the HR dropping to ∼0.2-0.3, compared with ∼0.4 during the failed state transitions studied by Soleri et al (2013) and Yoshikawa et al (2015).…”

Section: An Unusual Soft Statementioning

confidence: 89%

“…The source has still not returned to quiescence, ∼10 years after its initial discovery, and has instead exhibited significant long-term (> 400 day) variability over the course of its prolonged 'outburst' (Shaw et al 2013). Swift J1753.5-0127 has remained as a persistent LMXB in the hard state for the majority of this time, however it has experienced a number of short-term spectral softenings, characterised by an increase in the inner disk temperature and simultaneous steepening of the power law component (Yoshikawa et al 2015). Investigation of the source during one such event with RXTE revealed that it had transitioned to the hard intermediate state.…”

Section: Introductionmentioning

confidence: 99%

A low-luminosity soft state in the short-period black hole X-ray binary Swift J1753.5-0127

Shaw¹,

Gandhi²,

Altamirano³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present results from the spectral fitting of the candidate black hole X-ray binary Swift J1753.5-0127 in an accretion state previously unseen in this source. We fit the 0.7-78 keV spectrum with a number of models, however the preferred model is one of a multi-temperature disk with an inner disk temperature kT in = 0.252±0.003 keV scattered into a steep power-law with photon index Γ = 6.39 +0.08 −0.02 and an additional hard power law tail (Γ = 1.79 ± 0.02). We report on the emergence of a strong disk-dominated component in the X-ray spectrum and we conclude that the source has entered the soft state for the first time in its ∼10 year prolonged outburst. Using reasonable estimates for the distance to the source (3 kpc) and black hole mass (5M ⊙ ), we find the unabsorbed luminosity (0.1-100 keV) to be ≈ 0.60% of the Eddington luminosity, making this one of the lowest luminosity soft states recorded in X-ray binaries. We also find that the accretion disk extended towards the compact object during its transition from hard to soft, with the inner radius estimated to be R in = 28.0 +0.7 −0.4 R g or ∼ 12R g , dependent on the boundary condition chosen, assuming the above distance and mass, a spectral hardening factor f = 1.7 and a binary inclination i = 55• .

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“…The spectral properties and X-ray variability of 4U 1954+11 find similarities with other BHCs in the soft spectral state (Swift J1753.5-0127 (Yoshikawa et al 2015), MAXI J1634-479 (Xu et al 2020) and MAXI J1535-571 (Cúneo et al 2020)). The evolution of the hard component to dominate the emission at the relatively high-flux states as observed during the epochs 6 and 7 provides strong evidence that it does not harbour a NS (Di Salvo et al 2000;Wijnands et al 2002).…”

Section: Discussionmentioning

confidence: 60%

Broad-band spectral study of LMXB black hole candidate 4U 1957+11 with NuSTAR

Sharma,

Jain

et al. 2021

Preprint

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We present here the results of broadband spectral analysis of low-mass X-ray binary and a black hole candidate 4U 1957+11. The source was observed nine times with the Nuclear Spectroscopic Telescope Array (NuSTAR) between 2018 September and 2019 November. During these observations, the spectral state of 4U 1957+11 evolved marginally.The disc dominant spectra are well described with a hot, multicolour disc blackbody with disc temperature varying in the range kT in ∼ 1.35-1.86 keV and a non-thermal component having a steep slope (Γ = 2-3). A broad Fe emission line feature (5-8 keV) was observed in the spectra of all the observations. The relativistic disc model was used to study the effect of distance, inclination, and the black hole mass on its spin. Simulations indicate a higher spin for smaller distances and lower black hole mass. At smaller distances and higher mass, spin is maximum and almost independent of the distance. An inverse correlation exists between the spin and the spectral hardening factor for all the cases. The system prefers a moderate spin of about 0.85 for black hole masses between 4-6 M for a 7 kpc distance.

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Repeated short-term spectral softening in the low/hard state of the Galactic black hole candidate Swift J1753.5−0127

Cited by 14 publications

References 22 publications

Disc–jet quenching of the galactic black hole Swift J1753.5−0127

Disc–jet quenching of the galactic black hole Swift J1753.5−0127

A low-luminosity soft state in the short-period black hole X-ray binary Swift J1753.5-0127

Broad-band spectral study of LMXB black hole candidate 4U 1957+11 with NuSTAR

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