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  • Oxford University Press (OUP)  (11)
  • Ji, L  (11)
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  • Oxford University Press (OUP)  (11)
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  • 1
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 493, No. 4 ( 2020-04-21), p. 5680-5692
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 493, No. 4 ( 2020-04-21), p. 5680-5692
    Abstract: We report on our analysis of the 2019 outburst of the X-ray accreting pulsar 4U 1901+03 observed with Insight-HXMT and NICER. Both spectra and pulse profiles evolve significantly in the decaying phase of the outburst. Dozens of flares are observed throughout the outburst. They are more frequent and brighter at the outburst peak. We find that the flares, which have a duration from tens to hundreds of seconds, are generally brighter than the persistent emission by a factor of ∼1.5. The pulse-profile shape during the flares can be significantly different from that of the persistent emission. In particular, a phase shift is clearly observed in many cases. We interpret these findings as direct evidence of changes of the pulsed beam pattern, due to transitions between the sub- and supercritical accretion regimes on a short time-scale. We also observe that at comparable luminosities the flares’ pulse profiles are rather similar to those of the persistent emission. This indicates that the accretion on the polar cap of the neutron star is mainly determined by the luminosity, i.e. the mass accretion rate.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
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  • 2
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 497, No. 4 ( 2020-10-01), p. 5498-5506
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 497, No. 4 ( 2020-10-01), p. 5498-5506
    Abstract: Based on Insight-HXMT data, we report on the pulse fraction evolution during the 2017–2018 outburst of the newly discovered first Galactic ultraluminous X-ray (ULX) source Swift J0243.6+6124. The pulse fractions of 19 observation pairs selected in the rising and fading phases with similar luminosity are investigated. The results show a general trend of the pulse fraction increasing with luminosity and energy at supercritical luminosity. However, the relative strength of the pulsation between each pair evolves strongly with luminosity. The pulse fraction in the rising phase is larger at luminosity below 7.71 × 1038 erg s−1, but smaller at above. A transition luminosity is found to be energy independent. Such a phenomenon is first confirmed by Insight-HXMT observations and we speculate that it may have relation with the radiation-pressure-dominated accretion disc.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 3
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 512, No. 3 ( 2022-04-07), p. 4541-4555
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 512, No. 3 ( 2022-04-07), p. 4541-4555
    Abstract: We studied the 2018 outburst of the black hole transient H 1743 − 322 with a series of Insight-HXMT, NICER, and NuSTAR observations, covering the 1–120 keV band. With our broad-band X-ray spectral modelling, we confirm that the source remained in the low/hard state throughout the month-long outburst, although it became marginally softer at peak flux. We detected Type-C quasi-periodic oscillations (QPOs) and followed the evolution of their properties. The QPO frequency increased from ∼0.1 to ∼0.4 Hz during the rising phase of the outburst and decreased again in the decline. Continuum X-ray flux, power-law photon index, QPO frequency, and QPO root-mean-square amplitude were positively correlated. The QPO amplitude was slightly higher in the soft X-ray band (typical values of 12–16 per cent, compared with 8–10 per cent in the hard band). Our spectral-timing results shed light on the initial rising phase in the low/hard state, which has rarely been monitored with such high cadence, time resolution, and broad-band coverage. Combining spectral and timing properties, we find that ‘failed’ (hard state only) and ‘successful’ outbursts follow the same initial evolutionary track, although the former class of outburst never reaches the threshold for a transition to softer (thermally dominated) accretion regimes.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
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  • 4
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2021
    In:  Monthly Notices of the Royal Astronomical Society Vol. 501, No. 2 ( 2021-01-06), p. 2522-2530
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 501, No. 2 ( 2021-01-06), p. 2522-2530
    Abstract: We investigate the absorption and emission features in observations of GX 301-2 detected with Insight-HXMT/LE in 2017–2019. At different orbital phases, we found prominent Fe Kα, Kβ, and Ni Kα lines, as well as Compton shoulders and Fe K-shell absorption edges. These features are due to the X-ray reprocessing caused by the interaction between the radiation from the source and surrounding accretion material. According to the ratio of iron lines (Kα and Kβ), we infer the accretion material is in a low ionization state. We find an orbital-dependent local absorption column density, which has a large value and strong variability around the periastron. We explain its variability as a result of inhomogeneities of the accretion environment and/or instabilities of accretion processes. In addition, the variable local column density is correlated with the equivalent width of the iron Kα lines throughout the orbit, which suggests that the accretion material near the neutron star is spherically distributed.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 2016084-7
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  • 5
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2019
    In:  Monthly Notices of the Royal Astronomical Society
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP)
    Abstract: We present a study of timing properties of the accreting pulsar 2S 1417-624 observed during its 2018 outburst, based on Swift/BAT, Fermi/GBM, Insight-HXMT and NICER observations. We report a dramatic change of the pulse profiles with luminosity. The morphology of the profile in the range 0.2-10.0 keV switches from double to triple peaks at ∼2.5 $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$ and from triple to quadruple peaks at ∼7 $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$. The profile at high energies (25-100 keV) shows significant evolutions as well. We explain this phenomenon according to existing theoretical models. We argue that the first change is related to the transition from the sub to the super-critical accretion regime, while the second to the transition of the accretion disc from the gas-dominated to the radiation pressure-dominated state. Considering the spin-up as well due to the accretion torque, this interpretation allows to estimate the magnetic field self-consistently at ∼7 × 1012 G.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2016084-7
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  • 6
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2019
    In:  Monthly Notices of the Royal Astronomical Society
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP)
    Abstract: We report on analysis of observations of the bright transient X-ray pulsar Swift J0243.6+6124 obtained during its 2017-2018 giant outburst with Insight-HXMT, NuSTAR, and Swift observatories. We focus on the discovery of a sharp state transition of the timing and spectral properties of the source at super-Eddington accretion rates, which we associate with the transition of the accretion disk to a radiation pressure dominated (RPD) state, the first ever directly observed for magnetized neutron star. This transition occurs at slightly higher luminosity compared to already reported transition of the source from sub- to super-critical accretion regime associate with onset of an accretion column. We argue that this scenario can only be realized for comparatively weakly magnetized neutron star, not dissimilar to other ultra-luminous X-ray pulsars (ULPs), which accrete at similar rates. Further evidence for this conclusion is provided by the non-detection of the transition to the propeller state in quiescence which strongly implies compact magnetosphere and thus rules out magnetar-like fields.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2016084-7
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  • 7
    In: European Heart Journal, Oxford University Press (OUP), Vol. 41, No. Supplement_2 ( 2020-11-01)
    Abstract: In patients with type 2 diabetes (T2D), optimal management of cardiovascular (CV) risk factors is critical for primary prevention of CV disease. Purpose To describe the association of country income and patient socioeconomic factors with risk factor control in patients with T2D. Methods DISCOVER is a 37-country, prospective, observational study of 15,983 patients with T2D enrolled between January 2016 and December 2018 at initiation of 2nd-line glucose-lowering therapy and followed for 3 years. In patients without known CV disease with sub-optimally controlled risk factors at baseline, we examined achievement of risk factor control (HbA1c & lt;7%, BP & lt;140/90 mmHg, appropriate statin) at the 3 year follow-up. Countries were stratified by gross national income (GNI)/capita, per World Bank report. We explored variability across countries in risk factor control achievement using hierarchical logistic regression models and examined the association of country- and patient-level economic factors with risk factor control. Results Among 9,613 patients with T2D but without CV disease (mean age 57.2 years, 47.9% women), 83.1%, 37.5%, and 66.3% did not have optimal control of glucose, BP, and statins, respectively, at baseline. Of these, 40.8%, 55.5%, and 28.6% achieved optimal control at 3 years of follow-up. There was substantial variability in achievement of risk factor control across countries (Figure) but no association of country GNI/capita on achievement of risk factor control (Table). Insurance status, which differed substantially by GNI group, was strongly associated with glycemic control, with no insurance and public insurance associated with lower odds of patients achieving HbA1c & lt;7%. Conclusions In a global cohort of patients with T2D, a substantial proportion do not achieve risk factor control even after 3 years of follow-up. The variability across countries in risk factor control is not explained by the GNI/capita of the country. Proportion of patients at goal Funding Acknowledgement Type of funding source: Private company. Main funding source(s): The DISCOVER study is funded by AstraZeneca
    Type of Medium: Online Resource
    ISSN: 0195-668X , 1522-9645
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2001908-7
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  • 8
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2021
    In:  Clinical and Experimental Immunology Vol. 204, No. 3 ( 2021-05-13), p. 361-372
    In: Clinical and Experimental Immunology, Oxford University Press (OUP), Vol. 204, No. 3 ( 2021-05-13), p. 361-372
    Abstract: Dedicator of cytokinesis 2 (Dock2), an atypical guanine exchange factor, is specifically expressed on immune cells and mediates cell adhesion and migration by activating Rac and regulates actin cytoskeleton remodeling. It plays a crucial role in the migration, formation of immune synapses, cell proliferation, activation of T and B lymphocytes and chemotaxis of pDCs and neutrophils. However, in-vivo physiological functions of Dock2 have been relatively seldom studied. Our previous studies showed that Dock2−/− mice were highly susceptible to colitis induced by Citrobacter rodentium infection, and in early infection, Dock2−/− mice had defects in macrophage migration. However, the specific roles of Dock2 in the migration and functions of macrophages are not clear. In this study, we found that the expression of chemokines such as chemokine (C-C motif) ligand (CCL)4 and CCL5 and chemokine receptors such as chemokine (C-C motif) receptor (CCR)4 and CCR5 in bone marrow-derived macrophages (BMDM) of Dock2−/− mice decreased after infection, which were supported by the in-vivo infection experimental results; the Transwell experiment results showed that Dock2−/− BMDM had a defect in chemotaxis. The bacterial phagocytic and bactericidal experiment results also showed that Dock2−/− BMDM had the defects of bacterial phagocytosis and killing. Furthermore, the adoptive transfer of wild-type BMDM alleviated the susceptibility of Dock2−/− mice to C. rodentium infection. Our results show that Dock2 affects migration and phagocytic and bactericidal ability of macrophages by regulating the expression of chemokines, chemokine receptors and their responses to chemokine stimulation, thus playing an essential role in the host defense against enteric bacterial infection.
    Type of Medium: Online Resource
    ISSN: 0009-9104 , 1365-2249
    RVK:
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 2020024-9
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  • 9
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 518, No. 2 ( 2022-11-26), p. 2521-2528
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 518, No. 2 ( 2022-11-26), p. 2521-2528
    Abstract: We study the spectral and temporal properties of the black hole X-ray transient binary MAXI J1820+070 during the 2018 outburst with Insight-HXMT observations. The outburst of MAXI J1820+070 can be divided into three intervals. For the two intervals of the outburst, we find that low-energy (below 140 keV) photons lag high-energy (140–170 keV) ones, while in the decay of the outburst, high-energy photons lag low-energy photons, both with a time-scale of the order of days. Based on these results, the canonical hysteresis effect of the ‘q’ shape in the hardness–intensity diagram can be reformed into a roughly linear shape by taking into account the lag corrections between different energy bands. Time analysis shows that the high-frequency break of hard X-rays, derived from the power-density spectrum of the first interval of the outburst, is in general larger and more variable than that of soft X-rays. The spectral fitting shows that the coverage fraction of the hard X-rays drops sharply at the beginning of the outburst to about 0.5, and then increases slightly. The coverage fraction drops to roughly zero once the source steps into soft state and increases gradually to unity when the source returns to low–hard state. We discuss the possible overall evolution scenario of corona hinted from these discoveries.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
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  • 10
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2023
    In:  Monthly Notices of the Royal Astronomical Society Vol. 525, No. 1 ( 2023-08-09), p. 595-606
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 525, No. 1 ( 2023-08-09), p. 595-606
    Abstract: MAXI J1816–195 is a newly discovered accreting millisecond X-ray pulsar that went outburst in 2022 June. Through timing analysis with Neutron star Interior Composition Explorer (NICER) and Nuclear Spectroscopic Telescope Array (NuSTAR) observations, we find a transient modulation at ~2.5 Hz during the decay period of MAXI J1816–195. The modulation is strongly correlated with a spectral hardening, and its fractional rms amplitude increases with energy. These results suggest that the modulation is likely to be produced in an unstable corona. In addition, the presence of the modulation during thermonuclear bursts indicates that it may originate from a disc-corona where the optical depth is likely the main factor affecting the modulation, rather than temperature. Moreover, we find significant reflection features in the spectra observed simultaneously by NICER and NuSTAR, including a relativistically broadened Fe-K line around 6–7 keV, and a Compton hump in the 10–30 keV energy band. The radius of the inner disc is constrained to be Rin  = (1.04–1.23) RISCO based on reflection modeling of the broad-band spectra. Assuming that the inner disc is truncated at the magnetosphere radius, we estimate that the magnetic field strength is $\le 4.67 \times 10^{8}\, \rm G$.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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