分类: 天文学 >> 天文学 提交时间: 2024-07-15 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: We present a comprehensive analysis of the 2021 outburst of MAXI J1803–298 utilizing observations of the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) spanning from the low hard state to the high soft state. Within the Insight-HXMT data set, compared to the previous work, we identify a more prolonged presence of type-C quasi-periodic oscillations (QPOs) with centroid frequencies ranging from ∼0.16 to 6.3 Hz, which present correlations with the hardness ratio and the photon index of the Comptonized component. For QPO frequencies less than ∼2 Hz, the QPO phase lags are hard (photons of 10–19 keV arrive later than those of 1–4 keV), while at higher frequencies, the lags become soft at and above ∼4 Hz. Furthermore, the spectra in all Insight-HXMT observations consist of a multi-color blackbody component and a Comptonized component, as commonly observed in classical black hole X-ray binaries. We analyze state transitions and the evolution of accretion geometry in this work. The fitted inner disk radius increases abnormally during the low hard state, hypothesized to result from the corona condensing onto the inner disk. Additionally, two significant drops in flux are observed during the soft intermediate state, maybe implying changes in the corona/jet and the disk, respectively.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-02-01 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Fast radio bursts (FRBs) are short pulses observed in radio frequencies usually originating from cosmological distances. The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154 suggests that at least some FRBs can be generated by magnetars. However, the majority of X-ray bursts from magnetars are not associated with radio emission. The fact that only in rare cases can an FRB be generated raises the question regarding the special triggering mechanism of FRBs. Here we report long time spin evolution of SGR J1935+2154 until the end of 2022. According to ν and , the spin evolution of SGR J1935+2154 could be divided into two stages. The first stage evolves relatively steady evolution until 2020 April 27. After the burst activity in 2020, the spin of SGR J1935+2154 shows strong variations, especially for . After the burst activity in 2022 October, a new spin-down glitch with Δν/ν = (–7.2 ± 0.6) × 10−6 is detected around MJD 59876, which is the second event in SGR J1935+2154. At the end, spin frequency and pulse profile do not show variations around the time of FRB 200428 and radio bursts 221014 and 221021, which supply strong clues to constrain the trigger mechanism of FRBs or radio bursts.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Proton radiography experiment with a Zumbro lens system was carried out on an 11 MeV proton cyclotron. The experimental results show that the image blurring is improved markedly. Clear images and good spatial resolution of the density step edges are obtained, which is important for hydrotest experiments, and the spatial resolution can achieve 100 m.
分类: 天文学 >> 天文学 提交时间: 2023-12-29
摘要: Magnetars are neutron stars with extremely strong magnetic fields, frequently powering high-energy activity in X-rays. Pulsed radio emission following some X-ray outbursts have been detected, albeit its physical origin is unclear. It has long been speculated that the origin of magnetars' radio signals is different from those from canonical pulsars, although convincing evidence is still lacking. Five months after magnetar SGR 1935+2154's X-ray outburst and its associated Fast Radio Burst (FRB) 20200428, a radio pulsar phase was discovered. Here we report the discovery of X-ray spectral hardening associated with the emergence of periodic radio pulsations from SGR 1935+2154 and a detailed analysis of the properties of the radio pulses. The complex radio pulse morphology, which contains both narrow-band emission and frequency drifts, has not been seen before in other magnetars, but is similar to those of repeating FRBs - even though the luminosities are many orders of magnitude different. The observations suggest that radio emission originates from the outer magnetosphere of the magnetar, and the surface heating due to the bombardment of inward-going particles from the radio emission region is responsible for the observed X-ray spectral hardening.