分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The disclosed satellite metadata as well as previous estimations using Revise Kinematic Precise Point Positioning (RKPPP) approach with L-band data have already demonstrated the continuous yaw steering model used by BDS-3 Medium Earth Orbit (MEO) satellites manufactured by China Academy of Space Technology (CAST) in deep eclipse seasons instead of the orbit normal mode. However, the yaw model has not been validated for MEO satellites manufactured by Shanghai Engineering Center of Microsatellites (SECM), as the horizontal phase center offsets (PCO) approaches zeros, similar for BDS-3 Inclined Geostationary Orbit (IGSO) satellites. In this study, the inter-satellite link (ISL) data were used to estimate the yaw angles of BDS-3 IGSO and MEO satellites with accuracy of around 1.49{\deg} to investigate their yaw behaviors, particularly in the deep eclipse seasons. The estimates confirm that the IGSO and MEO satellites from CAST show the similar yaw behaviors, while the SECM MEO satellites do not fully comply with the attitude law published by China Satellite Navigation Office (CSNO). The attitude transition postpones from that predicted by CSNO yaw law, and occurs when the yaw angle is less than 5{\deg} and the elevation angle of the Sun above the orbital plane (beta angle) crosses 0{\deg}. The transition completes within three minutes with a rate about 0.055{\deg}/s. A model is proposed to predict these behaviors, and the ISL residuals return to normal levels, and became more stable in the adjacent of midnight and noon points. Once the yaw models are used.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Wan-Min Zheng
Qiaoya Wu
Jianfeng Wu
Song Wang
Mouyuan Sun
Jing Guo
Junhui Liu
Tuan Yi
Zhi-Xiang Zhang
Wei-Min Gu
Junfeng Wang
Lijun Gou
Jifeng Liu
Paul J. Callanan
Luis C. Ho
Penélope Longa-Peña
Jerome A. Orosz
Mark T. Reynolds
摘要： The optical light curves of quiescent black hole low-mass X-ray binaries often exhibit significant non-ellipsoidal variabilities, showing the photospheric radiation of the companion star is veiled by other source of optical emission. Assessing this "veiling" effect is critical to the black hole mass measurement. Here in this work, we carry out a strictly simultaneous spectroscopic and photometric campaign on the prototype of black hole low-mass X-ray binary A0620-00. We find that for each observation epoch, the extra optical flux beyond a pure ellipsoidal modulation is positively correlated with the fraction of veiling emission, indicating the accretion disk contributes most of the non-ellipsoidal variations. Meanwhile, we also obtain a K2V spectral classification of the companion, as well as the measurements of the companion's rotational velocity $v \sin i = 83.8\pm1.9$ km s$^{-1}$ and the mass ratio between the companion and the black hole $q=0.063\pm0.004$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Tuan Yi
Wei-Min Gu
Zhi-Xiang Zhang
Ling-Lin Zheng
Mouyuan Sun
Junfeng Wang
Zhongrui Bai
Pei Wang
Jianfeng Wu
Yu Bai
Song Wang
Haotong Zhang
Yize Dong
Yong Shao
Xiang-Dong Li
Jia Zhang
Yang Huang
Fan Yang
Qingzheng Yu
Hui-Jun Mu
摘要： Optical time-domain surveys can unveil and characterize exciting but less-explored non-accreting and/or non-beaming neutron stars (NS) in binaries. Here we report the discovery of such a NS candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9+400736 (hereafter J1123), is in a single-lined spectroscopic binary containing an optically visible M star. The star's large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200-inch telescope and high-precision photometry from TESS, we measure a companion mass of $1.24_{-0.03}^{+0.03}~M_{\odot}$. Main-sequence stars with this mass are ruled out, leaving a NS or a massive white dwarf (WD). Although a massive WD cannot be ruled out, the lack of UV excess radiation from the companion supports the NS hypothesis. Deep radio observations with FAST yielded no detections of either pulsed or persistent emission. J1123 is not detected in numerous X-ray and gamma-ray surveys. These non-detections suggest that the NS candidate is not presently accreting and pulsing. Our work exemplifies the capability of discovering compact objects in non-accreting close binaries by synergizing the optical time-domain spectroscopy and high-cadence photometry.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Tuan Yi
Wei-Min Gu
Zhi-Xiang Zhang
Ling-Lin Zheng
Mouyuan Sun
Junfeng Wang
Zhongrui Bai
Pei Wang
Jianfeng Wu
Yu Bai
Song Wang
Haotong Zhang
Yize Dong
Yong Shao
Xiang-Dong Li
Jia Zhang
Yang Huang
Fan Yang
Qingzheng Yu
Hui-Jun Mu
摘要： Optical time-domain surveys can unveil and characterize exciting but less-explored non-accreting and/or non-beaming neutron stars (NS) in binaries. Here we report the discovery of such a NS candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9+400736 (hereafter J1123), is in a single-lined spectroscopic binary containing an optically visible M star. The star's large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200-inch telescope and high-precision photometry from TESS, we measure a companion mass of $1.24_{-0.03}^{+0.03}~M_{\odot}$. Main-sequence stars with this mass are ruled out, leaving a NS or a massive white dwarf (WD). Although a massive WD cannot be ruled out, the lack of UV excess radiation from the companion supports the NS hypothesis. Deep radio observations with FAST yielded no detections of either pulsed or persistent emission. J1123 is not detected in numerous X-ray and gamma-ray surveys. These non-detections suggest that the NS candidate is not presently accreting and pulsing. Our work exemplifies the capability of discovering compact objects in non-accreting close binaries by synergizing the optical time-domain spectroscopy and high-cadence photometry.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We demonstrate a novel approach to achieve wavelength-tunable ultrashort pulses from an all-fiber mode-locked laser with a saturable absorber based on nonlinear Kerr beam clean-up effect. This saturable absorber was formed by a single-mode fiber spliced to a graded-index multimode fiber, and its tunable band-pass filter effect is studied by a numerical model. By adjusting the bending condition of graded-index multimode fiber, the laser could produce dissipative soliton pulses with their central wavelength tunable from1040 nm to 1063 nm. The pulse width of output laser could be compressed externally to 791 fs, and the signal to noise ratio of its radio frequency spectrum was measured to be 75.5 dB. This work provides a new idea for the design of wavelength-tunable mode-locked laser which can be used as an attractive light source in communication system.
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