We present time-resolved optical spectroscopy of the `redback' binary millisecond pulsar system PSR J1023+0038 during both its radio pulsar (2009) and accretion disc states (2014 and 2016). We provide observational evidence for the companion star being heated during the disc-state. We observe a spectral type change along the orbit, from G5 to F6 at the secondary star's superior and inferior conjunction, respectively, and find that the corresponding irradiating luminosity can be powered by the high energy accretion luminosity or the spin-down luminosity of the neutron star. We determine the secondary star's radial velocity semi-amplitude from the metallic (primarily Fe and Ca) and Halpha absorption lines during these different states. The metallic and Halpha radial velocity semi-amplitude determined from the 2009 pulsar-state observations allows us to constrain the secondary star's true radial velocity K_2=276.3+/-5.6 km/s and the binary mass ratio q=0.137+/-0.003. By comparing the observed metallic and Halpha absorption-line radial velocity semi-amplitudes with model predictions, we can explain the observed semi-amplitude changes during the pulsar-state and during the pulsar/disc-state transition as being due to different amounts of heating and the presence of an accretion disc, respectively.
Modeling Multi-wavelength Pulse Profiles of Millisecond Pulsar PSR B1821-24
PSR B 1821 $-$ 24是一颗单毫秒脉冲星（MSP），辐射多波长脉冲光子。它具有复杂的无线电，X射线和$γ$射线脉冲轮廓，具有独特的峰值相位分离，挑战了传统的焦散辐射模型。采用单极环形隙模型，通过适当的磁倾角（$α=40^\circ$）和视角（$ζ=75^\circ$），我们成功地再现了它的三个波段的脉冲轮廓。结果表明，中间的射电峰起源于高海拔的核心间隙区，而另外两个射电峰则起源于相对低海拔的环形间隙区。X射线和$γ$射线波段的两个峰基本上都起源于环形间隙区，而从芯间隙区产生的$γ$射线发射对第一个$γ$射线峰有一定贡献。精确再现PSR B1821 $-$ 24的多波长脉冲轮廓使我们能够理解不同波段的发射区域，并证明脉冲星发射模型。
Prospects of constraining the dense matter equation of state from the timing analysis of pulsars in double neutron star binaries: the cases of PSR J0737-3039A and PSR J1757-1854
Do all millisecond pulsars share a common heritage?
低质量X射线双星系统中中子星毫秒脉动的发现证实了毫秒射电双星与低质量X射线双星系统之间的联系。从那时起，从LMXB产生毫秒射电双星，然后由于偶极辐射而自旋下降的过程被认为是毫秒射电双星的“标准进化”。然而，是否所有观测到的毫秒射电暴都可以由LMXB产生的问题直到现在还没有得到定量的解决。标准的演化过程产生的毫秒周期（P）和自旋下降速率（Pdot）并不完全独立。毫秒级射电望远镜可能达到的P-Pdot值受到联合约束。为了检验观测到的毫秒射电天体是否是毫秒X射线天体（MSXP）的明确后代，我们制作了一张概率图，它代表了标准模型下毫秒射电天体的预期分布。我们以超过95%的置信度表明，在标准模型的框架内，所观测到的毫秒X射线天体不能产生具有高磁场的最快旋转毫秒射电天体，例如PSR B 1937 +21。
