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	Revisit the periodicity of SGR J1935+2154 bursts with updated sample 期刊论文 OAI收割 Monthly Notices of the Royal Astronomical Society, 2022, 卷号: 517, 期号: 3, 页码: 3854-3863 作者: Xie, Sheng-Lun; Cai, Ce; Xiong, Shao-Lin; Yu, Yun-Wei; Zhang, Yan-Qiu \| 收藏 \| 浏览/下载：13/0 \| 提交时间：2023/11/10 methods: data analysis stars: magnetars Astrophysics - High Energy Astrophysical Phenomena
	Synchronous X-ray/Optical QPOs from the Black Hole LMXB MAXI J1820+070 期刊论文 OAI收割 Monthly Notices of the Royal Astronomical Society, 2021 作者: HXMT \| 收藏 \| 浏览/下载：52/0 \| 提交时间：2022/02/08 black hole physics Low Mass X-ray Binaries accretion accretion discs stars: individual (MAXI J1820+070) Astrophysics - High Energy Astrophysical Phenomena Abstract: We present high-speed optical photometry from SAAO and SALT on the black hole LMXB MAXI J1820+070 (ASSASN-18ey), some of it simultaneous with NICER, Swift and Insight-HXMT X-ray coverage. We detect optical Quasi-Periodic Oscillations (QPOs) that move to higher frequencies as the outburst progresses, tracking both the frequency and evolution of similar X-ray QPOs previously reported. Correlated X-ray/optical data reveal a complex pattern of lags, including an anti-correlation and a sub-second lag that evolve over the first few weeks of outburst. They also show correlated components separated by a lag equal to the QPO period roughly centered on zero lag, implying that the inter-band variability is strongly and consistently affected by these QPOs at a constant phase lag of roughly ±Ю The synchronisation of X-ray and optical QPOs indicates that they must be produced in regions physically very close to each other we thus propose that they can be explained by a precessing jet model, based on analogies with V404 Cyg and MAXI J1348-630.
	Periodicity Search on X-Ray Bursts of SGR J1935+2154 Using 8.5 yr of Fermi/GBM Data 期刊论文 OAI收割 The Astrophysical Journal, 2021, 卷号: 923, 页码: L30 作者: HXMT \| 收藏 \| 浏览/下载：21/0 \| 提交时间：2022/02/08 2008 1471 Astrophysics - High Energy Astrophysical Phenomena Abstract: We performed a systematic search for X-ray bursts of the SGR J1935+2154 using the Fermi Gamma-ray Burst Monitor continuous data dated from 2013 January to 2021 October. Eight bursting phases, which consist of a total of 353 individual bursts, are identified. We further analyze the periodic properties of our sample using the Lomb-Scargle periodogram. The result suggests that those bursts exhibit a period of ~238 days with a ~63.2% duty cycle. Based on our analysis, we further predict two upcoming active windows of the X-ray bursts. Since 2021 July, the beginning date of our first prediction has been confirmed by the ongoing X-ray activities of the SGR J1935+2154.
	THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope 期刊论文 OAI收割 The Astrophysical Journal, 2020, 卷号: 897, 期号: 2, 页码: 38 作者: Broderick, Avery E.; Gold, Roman; Karami, Mansour; Preciado-López, Jorge A.; Tiede, Paul \| 收藏 \| 浏览/下载：47/0 \| 提交时间：2020/08/24 Astrophysical black holes Galactic center Astronomy data analysis Very long baseline interferometry Submillimeter astronomy
	No pulsed radio emission during a bursting phase of a Galactic magnetar 期刊论文 OAI收割 Nature, 2020, 卷号: 587, 页码: 63-65 作者: HXMT \| 收藏 \| 浏览/下载：44/0 \| 提交时间：2022/02/08 Astrophysics - High Energy Astrophysical Phenomena Abstract: Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances^1-3. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources^4-13, but no convincing evidence has been collected so far¹⁴. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft íray bursts¹⁵. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft íray/hard-X-ray flare^18-21. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-íray repeater (SGR) bursts were detected in íray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB-SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.
	The braking index of PSR B0540-69 and the associated pulsar wind nebula emission after spin-down rate transition 期刊论文 OAI收割 Monthly Notices of the Royal Astronomical Society, 2020, 卷号: 494, 页码: 1865-1870 作者: HXMT \| 收藏 \| 浏览/下载：54/0 \| 提交时间：2022/02/08 stars: magnetic field stars: neutron pulsars: general Astrophysics - High Energy Astrophysical Phenomena Abstract: In 2011 December, PSR B054-69 experienced a spin-down rate transition (SRT), after which the spin-down power of the pulsar increased by $\sim 36{{\ \rm per\ cent}}$. About 1000 d after the SRT, the X-ray luminosity of the associated pulsar wind nebula (PWN) was found to brighten by $32\pm 8{{\ \rm per\ cent}}$. After the SRT, the braking index n of PSR B0540-69 changes from n = 2.12 to 0.03 and then keeps this value for about five years before rising to n = 0.9 in the following years. We find that most of the current models have difficulties in explaining the measured braking index. One exceptive model of the braking index evolution is the increasing dipole magnetic field of PSR B0540-69. We suggest that the field increase may result from some instabilities within the pulsar core that enhance the poloidal component at the price of toroidal component of the magnetic field. The increasing dipole magnetic field will result in the X-ray brightening of the PWN. We fit the PWN X-ray light curve by two models: one assumes a constant magnetic field within the PWN during the brightening and the other assumes an enhanced magnetic field proportional to the energy density of the PWN. It appears that the two models fit the data well, though the later model seems to fit the data a bit better. This provides marginal observational evidence that magnetic field in the PWN is generated by the termination shock. Future high-quality and high-cadence data are required to draw a solid conclusion.
	Insight-HXMT observations of Swift J0243.6+6124: the evolution of RMS pulse fractions at super-Eddington luminosity 期刊论文 OAI收割 Monthly Notices of the Royal Astronomical Society, 2020, 卷号: 497, 页码: 5498-5506 作者: HXMT \| 收藏 \| 浏览/下载：44/0 \| 提交时间：2022/02/08 stars: neutron pulsars: individual: Swift J0243.6+6124 X-rays: binaries Astrophysics - High Energy Astrophysical Phenomena 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.
	GRB 200415A: A Short Gamma-Ray Burst from a Magnetar Giant Flare? 期刊论文 OAI收割 The Astrophysical Journal, 2020, 卷号: 899, 页码: 106 作者: HXMT \| 收藏 \| 浏览/下载：39/0 \| 提交时间：2022/02/08 Gamma-ray bursts Soft gamma-ray repeaters Magnetars Gamma-ray transient sources 629 1441 992 1853 Astrophysics - High Energy Astrophysical Phenomena Abstract: The giant flares of soft gamma-ray repeaters (SGRs) have long been proposed to contribute to at least a subsample of the observed short gamma-ray bursts (GRBs). In this paper, we perform a comprehensive analysis of the high-energy data of the recent bright short GRB 200415A, which was located close to the Sculptor galaxy. Our results suggest that a magnetar giant flare provides the most natural explanation for most observational properties of GRB 200415A, including its location, temporal and spectral features, energy, statistical correlations, and high-energy emissions. On the other hand, the compact star merger GRB model is found to have difficulty reproducing such an event in a nearby distance. Future detections and follow-up observations of similar events are essential to firmly establish the connection between SGR giant flares and a subsample of nearby short GRBs.
	Ghost Image Correction in CSTAR Photometry 期刊论文 OAI收割 PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 2013, 卷号: 125, 期号: 930, 页码: 1015-1020 作者: Meng, Zeyang; Zhou, Xu; Zhang, Hui; Zhou, Jilin; Wang, Songhu 收藏 \| 浏览/下载：30/0 \| 提交时间：2016/11/11 Astrophysical Data