From multicolor-photometric observations to a guaranteed mass of AL Cas

We utilize the PAdova and TRieste Stellar Evolution Code(PARSEC) combined with photometric observations to determine a guaranteed mass of AL Cas and re-examine its related physical parameters.Multicolor-photometric observations of AL Cas have been performed in 2016 and 2017. We use the WilsonDevinney(W-D) code to analyze the light curves and find that AL Cas is probably an A-subtype contact binary(f = 35.7±0.9%) with a mass ratio q = 0.6399±0.0230 and an effective temperature difference?T = 78 K. The mass-radius relation of a higher luminosity component for AL Cas is obtained by two methods: depending on calculation of the Roche lobe(DCRL method) and depending on calculation of the W-D code(DCWD method). Using this relationship with the PARSEC model, we investigate the component masses of AL Cas as M1 = 1.19±0.23 M⊙ with M2 = 0.76±0.18 M⊙ by the DCRL method and M1 = 1.22±0.26 M⊙ with M2 = 0.78±0.20 M ⊙ by the DCWD method. By means of the photometric studies, we examine the related physical properties of AL Cas with the latest findings. We update the orbital period(Porb = 0.50055593 d) of AL Cas according to six new times of light minimum together with those collected from the literature. Meanwhile, the(O-C)2 curve analysis suggests that the orbital period of AL Cas has a cyclic variation with a period of 81.25 yr and an amplitude of 0.01415 d. This cyclic change would be caused by the light-travel time effect from a third body. A similar mass of the third body(M3 sin i′= 0.279 M⊙) is derived from our two methods.

High Spatial Resolution X-Ray Spectroscopy of Cas A with Chandra

We present high spatial resolution X-ray spectroscopy of the supernova remnant Cassiopeia A with the Chandra observations. The X-ray emitting region of this remnant was divided into 38 × 34 pixels of 10″× 10″ each. Spectra of 960 pixels were created and fitted with an absorbed two component non-equilibrium ionization model. From the results of the spectral analysis we obtained maps of absorbing column density, temperatures, ionization ages, and the abundances of Ne, Mg, Si, S, Ca and Fe. The Si, S and possibly Ca abundance maps show obvious jet structures, while Fe does not follow the jet but seems to be distributed perpendicular to it. The abundances of Si, S and Ca show tight correlations between one another over a range of about two dex. This suggests that they are ejecta from explosive O- burning and incomplete Si-burning. Meanwhile, the Ne abundance is well correlated with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The Fe abundance is positively correlated with that of Si when the latter is lower than 3 times the solar value, and is negatively correlated when higher. We suggest that such a two phase correlation is due to the different ways in which Fe was synthesized.

MHD simulations of inward shocks in Cassiopeia A

Cassiopeia A,the brightest radio supernova remnant(SNR)in the sky,has several unique characteristics in comparison to its peers.Besides its radio brightness and prominent soft-concave radio spectrum,itsγ-ray spectrum appears to have a low-energy cutoff near 2 GeV,and it is the only SNR with prominent hard X-ray emission.While the unusual radio properties may be attributed to strong emission from reverse shocks,the hard X-ray emission has been associated with high-speed inward shocks induced by high density gases.Then,the low-energyγ-ray spectral cutoff could be attributed to slow penetration of lower energy particles accelerated near the inward shocks into high-density emission zone.In this paper,we carry out magneto-hydrodynamic(MHD)simulations of shocks in Cassiopeia A and demonstrate that its inward shock structure can indeed be reproduced via shock interactions with clumps of gases with a density of 20 cm-3.

Hints of a second explosion(a quark nova) in Cassiopeia A supernova

We show that the explosive transition of the neutron star （NS） to a quark star （QS） （a Quark Nova） in Cassiopeia A （Cas A） a few days following the supernova （SN） proper can account for several of the puzzling kinematic and nucleosynthetic features that are observed. The observed decoupling between Fe and 44Ti and the lack of Fe emission within 44Ti regions is expected in the QN model owing to the spallation of the inner SN ejecta by relativistic QN neutrons. Our model predicts the 44Ti to be more prominent to the NW of the central compact object （CCO） than in the SE and little of it along the NE-SW jets, in agreement with NuStar observations. Other intriguing features of Cas A are addressed, such as the lack of a pulsar wind nebula and the reported few percent drop in the CCO temperature over a period of 10 yr.

Cassiopeia产品线

在竞争者纷纷推出基于微软最新的PDA操作系统的型号后,Casio也发布了它的Casio Cassiopeia E-200 Pocket PC 2002(报价600美元),至此他们终于又站在了一条起跑线上虽然E-200是一个可靠和完善的设备(它包括64MB RAM,CompactFlash TypeⅡ和Secure Digital/MultiMedia Card扩展槽),但它也没有什么特别与众不同的功能。 E-200使用USB连接,配置了206MHz的Intel StrongARM处理器和65536色的背光式TFT显示屏,在各种照明条件下使用时后者的表现都令我们非常满意。7盎司重的E-200尺寸大小为5.0×3.1×0.6英寸(长宽高)。银色和亮紫色的金属外壳可能比外观漂亮的HP Jornada 568和Toshiba PocketPC e560更容易引起保守用户的兴趣。不过,我们发现它存在两个小问题:一是MMC插槽的翻盖不好打开。

卡西欧Cassiopeia E-125

这款同样是由卡西欧所推出的Cassiopeia E-125(以下简称E-125),和以前推出的Cassiopeia E-115极为类似,除了E-125采用较具质感的铝银色外壳不一样外,不论是外形还是体积上都几乎一模一样,似乎是第二代E-115 Pocket PC.此款产品的主要特色是挟带着E-115的硬件优势,进一步将内部配置升级,它采用NEC VR4122 MIPS150MHz处理器,内置32MBRAM、16MB ROM,执行速度很流畅,且对于想要安装较多应用程序的使用者来说,也不必担心内存不足.

迷人的仙后座

仙后座（Cassiopeia）是秋天的代表星座之一，它的五颗亮量呈英文“W”状，高挂在星空，非常容易辨认。仙后座位于天球北极附近，介于英仙座、仙王座与仙女座之间，隔着北极星与大熊座遥遥相对。在星座与希腊神话故事中，仙后座是埃塞俄比亚国王后卡西奥帕亚的化身，据说她是一位美丽又受慕虚荣的皇后，她因虚荣与傲慢触怒的海神，最后导致他的女儿（后来被提升为仙女座）险些成为鲸鱼怪的祭品，幸好被英雄珀尔修斯所救（详见上期星空漫步：古埃塞俄比亚的国王——仙王座）。