XPer的新发射相：光谱与红外观测

ＸＰｅｒ的新发射相：光谱与红外观测杭恒荣，夏剑萍中国科学院紫金山天文台，南京２１０００８中国科学院光学天文联合实验室关键词Ｂｅ星／Ｘ射线双星，发射线，ＪＨＫ测光１引言ＸＰｅｒ是一颗Ｂｅ／Ｘ射线双星（４Ｕ０３５２＋３０）的光学对应体［１－３］，中子星的...     

恒星形成区NGC7538中的分子氢发射

报告在ＮＧＣ７５３８中利用Ｈ２（２．１２μｍ）发射线测新发现的两个喷流和１８个近红外ＨＨ天体,在ＩＲＳ１－３星云中观测到了强Ｈ２发射壳层结构环绕在星云的北边。星云中红外源的ＵＶ辐射场的外流活动都可能导致这一Ｈ２发射。在ＨＲＳ１－３星云的南边和东边探测到了５个Ｈ２ｋｎｏｔｓ．在ＩＲＳ１南边发现的Ｈ２喷流暗示该区域有一个南北向的外流,在ＩＲＳ１１星团的周围发现了９个Ｈ２ｈｎｏｔｓ．在西北－东南方向和东     

微U型爆发及微波精细结构

我们用新的时间分辨率短至８ｍｓ 的２ ．６ ～３ ．８ＧＨｚ 微波动态频谱仪在１９９８ 年４ 月１５ 日爆发和１９９７ 年１１ 月３ 日爆发中发现了微Ｕ 型爆发。其顶部频率为３ ．２ ～３ ．４ＧＨｚ（ 相应的等离子体密度：基波：１ ．２ ×１０１１ － １ ．４ ×１０１１／ｃｍ ３ ,二次谐波：３ ．２ ×１０１０ － ３ ．５ ×１０１０／ｃｍ ３） ;根部频率为３ ．４ ～３ ．６ＧＨｚ;单个Ｕ 型爆发的频率范围为６０ ～２２０ ＭＨｚ ;上升段频漂率为７ ～２８ＧＨｚ／ｓ;上升段持续时间为８ ～２４ｍｓ;寿命为１６ ～４８ｍｓ;偏振度大于８０ ％ 。在活动区为偶极子磁场的假设下,估计源区高度约为１ ．３ ×１０４ 公里,单一环的高度为２５０ ～８００ 公里。由此得出结论：１ ．由于高频漂率和高偏振度,似乎发现的微Ｕ 型爆发不是Ⅲ型爆发形成,而是尖峰辐射（Ｓｐｉｋｅ） 形成。２ ．我们发现的是小尺度的微磁环,其尺度与Ｓｐｉｋｅ 辐射的寿命相当。我们在１９９７ 年１１ 月２ 日的爆发中发现平均周期为数十ｍｓ 的准周期振荡群。在高密度流管的磁声波ＭＨＤ 振荡条件下,可取得磁环半径约９０ 公里的结果。由此可以得到微磁环物理尺度的图象     

导航型GPS接收机定时精度的分析

“能提供廉价并满足准确度达到或优于１μｓ的产业需求的世界范围内的时号传播”仍然是ＣＣＩＲ第７研究组的研究课题．为此，我们测量了４种型号的１３台导航星ＧＰＳ接收机输出的１ｐｐｓ与陕西天文台主钟ＵＴＣ（ＣＳＡＯＭＣ）的时间偏差．经电缆延迟和主钟相对子ＵＴＣ（ＣＳＡＯ）的钟差改正，测量结果表明，单次（采样时间约３０ｓ）定时测量的精度约为０．２μｓ，准确度为１～３μｓ；不同型号的ＧＰＳ接收机的硬件延时、测量偏倚误差和接收机噪声特性各不相同．只有测定这些接收机的时钟偏差并加以改正，才能达到准确度优于１μｓ的定时精度或时间同步精度。     

Taurus—Auriga外围区ROSAT定点观察选WTTS的光学证认与研究

低质量恒星形成区Ｔａｕｒｕｓ－Ａｕｒｉｇａ外围区ＲＯＳＡＴ定点观测选弱发射线Ｔ Ｔａｕｒｉ星候选体（ＷＴＴＳ）的光谱证认新发现４个ＷＴＴＳ。本给出了目标源的ＵＳＮＯ Ｒ星等、ＵＳＮＯ坐标（Ｊ２０００）、分类光谱型、Ｈα发射／吸收线和富ＬｉＸ射线源,包括新发现ＷＴＴＳ的ＬｉＩ吸收线强度等参量以及ＷＴＴＳ的特征光谱。并利用Ｈｉｐｐａｒｃｏｓ星表对部分目标源进行了视差和自行的研究。另外,本第一次给出     

XRB、SGR和GRB简介

ＸＲＢ、ＳＧＲ和ＧＲＢ简介Ｘ射线爆发（Ｘ－ｒａｙＢｕｒｓｔｅｒｓ，以下简称ＸＲＢ）、软γ射线复现（Ｓｏｆｔ－ｇａｍｍａＲｅｐｅａｔｅｒｓ，以下简称ＳＧＲ）和γ射线爆发（γ－ｒａａＢｕｒｓｔｅｒｓ，以下简称ＧＲＢ）都是天空中暂现、转瞬即逝的高能现象，三...     

星族综合模型与星系的颜色演化

本文利用Ｂｅｒｔｅｌｉ等人新算出的等龄线，以及Ｇｕｎｎ和Ｓｔｒｙｋｅｒ观测的恒星光谱（３１３０－１０８００）构造了一个星族综合模型．该模型能预计金属丰度在Ｚ＝０．０００４－０．０５，年龄在１０７－２×１０１０年范围内的简单星族（ＳＳＰ）的光谱能量分布（ＳＥＤ）．利用ＳＳＰ，通过对不同时刻恒星形成率的卷积能够得到星系的ＳＥＤ的演化．我们计算出ＳＳＰ以及星系在ＵＢＶＲＩ系统和ＢＡＴＣ１５色中带测光系统中的颜色．计算出的从Ｅ／ＳＯ到Ｓｄｍ各类星系的ＵＢＶＲＩ颜色在年龄为１２Ｇｙｒ时都和观测符合较好．因此，我们的模型为正在进行的关于星系ＳＥＤ的多色测光研究提供了理论上的探索．     

1ES1853-379的EGRET观测上限对其自转参数的限制

给出了来自新发现的孤立中子星１ＥＳ１８５３－３７９方向的γ射线上限为５×１０－８ｐｈｃｍ－２ｓ－１．假设γ射线辐射的立体角的成束和１ＧｅＶ的平均光子能量,对应的１光度上限为７．６×１０~２３（Ｄ／１００ｐｃ）２Ｊ／ｓ．导出的γ射线辐射效率上限比极冠模型或外间隙模型所预期的辐射效率低两个量级．由此给出了这一中子星自转参数的限制．     

晚型双星UX Ari的多频射电观测研究

用美国甚大阵（ＶＬＡ）对色球活动性双星系统ＵＸＡｒｉ进行了从１．４ＧＨｚ到１５ＧＨｚ范围内五个频段的观测，观测期间ＵＸＡｒｉ处于活动性比较低的阶段，射电光度为（６．６－１２．６）×１０１６ｅｒｇｓ－１Ｈｚ－１．射电频谱低频部分比较平坦，高频呈幂律形式，低频的圆偏振度很低，趋于零，高频辐射有中等圆偏振度（１５％）．射电发射机制可能是回旋同步加速机制，由此我们估计出发射区的磁场强度为几至几十高斯，相对论电子密度为～１０４－１０２ｃｍ－３量级，热电子数密度～１０８ｃｍ－３。     

OMC—3的^13CO（1—0）和C^18O（1—0）分子辐射

利用紫金山天台青海站的１３．７ｍ毫米波望远镜,对ＯｒｉｏｎＡ分子云中的ＯＭＣ－３区域,进行了较高分辨率的＾１３ＣＯ（Ｊ＝１－０）和Ｃ＾１８Ｏ（Ｊ＝１－０）分子辐射的图观测,给出了该分子云中＾１３ＣＯ和Ｃ＾１８Ｏ的云核中心分别与最年龄的天体－Ｃｌａｓｓ０类源ＭＭＳＩ,ＭＭＳ４,ＭＭＳ６和ＭＭＳ７,ＭＭＳ８,ＭＭＳ９成协,此外,通过分析ＯＭＣ－３整个区域的速度场结构,发现沿Ｃ＾１８Ｏ和＾１３ＣＯ云核     

Spectra of the spreading layers on the neutron star surface and constraints on the neutron star equation of state

Spectra of the spreading layers on the neutron star surface are calculated on the basis of the Inogamov–Sunyaev model taking into account general relativity correction to the surface gravity and considering various chemical composition of the accreting matter. Local (at a given latitude) spectra are similar to the X-ray burst spectra and are described by a diluted blackbody. Total spreading layer spectra are integrated accounting for the light bending, gravitational redshift and the relativistic Doppler effect and aberration. They depend slightly on the inclination angle and on the luminosity. These spectra also can be fitted by a diluted blackbody with the colour temperature depending mainly on a neutron star compactness. Owing to the fact that the flux from the spreading layer is close to the critical Eddington, we can put constraints on a neutron star radius without the need to know precisely the emitting region area or the distance to the source. The boundary layer spectra observed in the luminous low-mass X-ray binaries, and described by a blackbody of colour temperature   T _c= 2.4 ± 0.1 keV  , restrict the neutron star radii to   R = 14.8 ± 1.5 km  (for a  1.4-M_⊙  star and solar composition of the accreting matter), which corresponds to the hard equation of state.     

Relativistic plasma diffusion: a possible source for neutron star magnetic fields

Plasma density gradient which is inherent to degenerate neutron star matter is shown to lead to large scale plasma diffusion and subsequent charge separation. The surface (internal) fields generated by the spinning separated charges are found to be dipolar with intensities of ≃ 10¹⁴ G (for the surface fields) very early in the life-time of a typical neutron star. The internal fields, on the other hand, are relatively much weaker. These fields, which in this case are also shown to be temperature dependent, decay as a result of neutrino and photon emissions. The decay law derived from equations of standard cooling calculations and the equation connecting the magnetic field and temperature is indicated to have two distinct modes, each corresponding to the two branches of a typical neutron star cooling curve. We have found that results derived from the decay law are consistent with observational findings. Based on the theory behind our new model, we have also argued to show that isolated millisecond and sub-millisecond pulsars might be very rare objects. This revised version was published online in July 2006 with corrections to the Cover Date.     

Neutron star mergers in the context of the hadron–quark phase transition

The long awaited event of the detection of a gravitational wave from a binary neutron star merger and its electromagnetic counterparts marked the beginning of a new era in observational astrophysics. The brand-new field of gravitational wave astronomy combined with multi-messenger observations will uncover violent, highly energetic astrophysical events that could not be explored before by humankind. This article focuses on the presumable appearance of a hadron–quark phase transition and the formation of regions of deconfined quark matter in the interior of a neutron star merger product. The evolution of density and temperature profiles inside the inner region of the produced hypermassive/supramassive neutron star advises an incorporation of a hadron–quark phase transition in the equation of state of neutron star matter. The highly densed and hot neutron star matter of the remnant populate regions in the QCD phase diagram where a non neglectable amount of deconfined quark matter is expected to be present. If a strong hadron–quark phase transition would happen during the post-merger phase, it will be imprinted in the spectral properties of the emitted gravitational wave signal and might give an additional contribution to the dynamically emitted outflow of mass.     

Breakdown of the Goldreich–Julian relation in a neutron star

The electromagnetic field in a magnetized neutron star and the underlying volume charges and currents are found. A general case of a rigidly rotating neutron star with infinite conductivity, arbitrary distribution of the internal magnetic field, arbitrarily changing angular velocity, and arbitrary surface velocity less than the velocity of light is considered. Quaternions are used to describe rotation and determine the magnetic field. It is shown that the charge density is not equal to and can exceed significantly the common Goldreich–Julian density. Moreover, corrections to the magnetic field due to stellar rotation are zero. For a rotating neutron star, twisting magnetic field lines causes charge accumulation and current flows. This fact shows a possible link between changing internal magnetic field topology and observed activity of neutron stars.     

Neutron star retention and millisecond pulsar production in globular clusters

We investigate the conditions by which neutron star retention in globular clusters is favoured. We find that neutron stars formed in massive binaries are far more likely to be retained. Such binaries are likely to then evolve into contact before encountering other stars, possibly producing a single neutron star after a common envelope phase. A large fraction of the single neutron stars in globular clusters are then likely to exchange into binaries containing moderate-mass main-sequence stars, replacing the lower-mass components of the original systems. These binaries will become intermediate-mass X-ray binaries (IMXBs), once the moderate-mass star evolves off the main sequence, as mass is transferred on to the neutron star, possibly spinning it up in the process. Such systems may be responsible for the population of millisecond pulsars (MSPs) that has been observed in globular clusters. Additionally, the period of mass-transfer (and thus X-ray visibility) in the vast majority of such systems will have occurred 5–10 Gyr ago, thus explaining the observed relative paucity of X-ray binaries today, given the MSP population.     

Models for the formation of binary and millisecond radio pulsars

The peculiar combination of a relatively short pulse period and a relatively weak surface dipole magnetic field strength of binary radio pulsars finds a consistent explanation in terms of (i) decay of the surface dipole component of neutron-star magnetic fields on a timescale of (2–5) × 10⁶ yr, in combination with (ii) spin-up of the rotation of the neutron star during a subsequent mass-transfer phase. The four known binary radio pulsars appear to fall into two different categories. Two of them, PSR 0655 + 64 and PSR 1913 + 16, have short orbital periods (<25 h) and high mass functions, indicating companion masses 0.7M⊙ (∼1 (± 0.3) M⊙ and 1.4 M⊙, respectively). The other two, PSR 0820 + 02 and PSR 1953 + 29, have long orbital periods (117d), nearly circular orbits, and low, almost identical mass functions of about 3×10^-3 M⊙, suggesting companion masses of about 0.3M⊙. It is pointed out that these two classes of systems are expected to be formed by the later evolution of binaries consisting of a neutron star and a normal companion star, in which the companion was (considerably) more massive than the neutron star, or less massive than the neutron star, respectively. In the first case the companion of the neutron star in the final system will be a massive white dwarf, in a circular orbit, or a neutron star in an eccentric orbit. In the second case the final companion to the neutron star will be a low-mass (∼ 0.3 M⊙) helium white dwarf in a wide and nearly circular orbit. In systems of the second type the neutron star was most probably formed by the accretion-induced collapse of a white dwarf. This explains in a natural way why PSR 1953 + 29 has a millisecond rotation period and PSR 0820 + 02 has not. Among the binary models proposed for the formation of the 1.5-millisecond pulsar, the only ones that appear to be viable are those in which the companion disappeared by coalescence with the neutron star. In such models the companion may have been a red dwarf of mass 0.03M⊙, a neutron star, or a massive (>0.7M⊙) white dwarf. Only in the last-mentioned case is a position of the pulsar close to the galactic plane a natural consequence. In the first-mentioned case the progenitor system most probably was a cataclysmic-variable binary in which the white dwarf collapsed by accretion.     

The effects of strong interaction on the observational discrimination between neutron and strange stars

Strange stars are compact objects similar to neutron stars composed of strange matter. This paper investigates the observational effects of the strong interaction between quarks. We believe: 1) that the conversion of a neutron star to a strange star is a large “period glitch” which is determined by the strong interaction; 2) that the strong interaction results in effective damping of oscillation of hot strange stars, which could be a new mechanism of driving supernova explosions; 3) that the strong interaction increases the difference in rotation between strange and neutron stars under high temperatures, making the minimum period for strange stars lower than that for neutron stars.     

软γ射线重爆GB790107的辐射机制

本文在中子星吸积彗星云模型的基础上,认为软重爆GB790107起源于弱磁化(B～10~8G)中子星,其阵雨式地吸积彗星云将在中子星表面形成一光厚辐射区,该辐射区的温度分布由激波模型确定.这一辐射区中的高温等离子体产生的黑体辐射将很好地拟合GB790107的观测能谱,且获得爆源距离为(1.35～13.5)pc.     

Heat blanketing envelopes and thermal radiation of strongly magnetized neutron stars

Strong (B?10⁹ G) and superstrong (B?10¹⁴ G) magnetic fields profoundly affect many thermodynamic and kinetic characteristics of dense plasmas in neutron star envelopes. In particular, they produce strongly anisotropic thermal conductivity in the neutron star crust and modify the equation of state and radiative opacities in the atmosphere, which are major ingredients of the cooling theory and spectral atmosphere models. As a result, both the radiation spectrum and the thermal luminosity of a neutron star can be affected by the magnetic field. We briefly review these effects and demonstrate the influence of magnetic field strength on the thermal structure of an isolated neutron star, putting emphasis on the differences brought about by the superstrong fields and high temperatures of magnetars. For the latter objects, it is important to take proper account of a combined effect of the magnetic field on thermal conduction and neutrino emission at densities ρ?10¹⁰ g?cm^?3. We show that the neutrino emission puts a B-dependent upper limit on the effective surface temperature of a cooling neutron star.     

Systematic variation in the apparent burning area of thermonuclear bursts and its implication for neutron star radius measurement

Precision measurements of neutron star radii can provide a powerful probe of the properties of cold matter beyond nuclear density. Beginning in the late 1970s, it was proposed that the radius could be obtained from the apparent or inferred emitting area during the decay portions of thermonuclear (type I) X-ray bursts. However, this apparent area is generally not constant, preventing a reliable measurement of the source radius. Here, we report for the first time a correlation between the variation of the inferred area and the burst properties, measured in a sample of almost 900 bursts from 43 sources. We found that the rate of change of the inferred area during decay is anticorrelated with the burst decay duration. A Spearman rank correlation test shows that this relation is significant at the  <10⁻⁴⁵  level for our entire sample, and at the  7 × 10⁻³⁷  level for the 625 bursts without photospheric radius expansion. This anticorrelation is also highly significant for individual sources exhibiting a wide range of burst durations, such as 4U 1636–536 and Aql X-1. We suggest that variations in the colour factor, which relates the colour temperature resulted from the scattering in the neutron star atmosphere to the effective temperature of the burning layer, may explain the correlation. This in turn implies significant variations in the composition of the atmosphere between bursts with long and short durations.