一颗与众不同的脉冲星Geminga

最近，一个困扰人们达十几年之久的γ射线源Ｇｅｍｉｎｇａ被证认为Ｘ、γ射线脉冲星，其光学对应体也被确定为一颗光谱偏蓝的２５等星。对Ｇｅｍｉｎｇａ脉冲星的确证说明存在着一类没有射电辐射的脉冲单星。     

脉冲星PSR1951＋32的X射线脉冲辐射

脉冲星ＰＳＲ１９５１＋３２的Ｘ射线脉冲辐射程凌翔，李惕碚，孙学军，马宇蒨，吴枚（中国科学院高能物理研究所，北京１０００３９）主题词：脉冲星－Ｘ射线源１９８７年６月，用频率３８７ＭＨｚ的射电观测发现了脉冲星ＰＳＲ１９５１＋３２［１］，同年７月，在１８０...     

Geminga缺射电脉冲的一种可能机制

应用Ｕｓｏｖ和Ｍｅｌｒｏｓｅγ射线脉冲星的修正的极冠区内间隙模型,得出了γ射线脉冲星Ｇｅｍｉｎｇａ为什么没有射电脉冲辐射或射电脉冲辐射很弱的一种可能解释．同时,也可看出,中子星表面的多极场有着重要的作用．     

脉冲星Geminga MeV脉冲辐射证据

利用直接解调方法分析ＣＯＭＰＴＥＬ ＶＰ１数据,得到了脉冲星Ｇｅｍｉｎｇａ １０－３０ＭｅＶ脉冲辐射存在的证据;全位相及分位相成像均得到了Ｇｅｍｉｎｇａ。分位相成像结果显示,江变曲线的峰值位于ｐｕｌｓｅ１附近,而闰相区域只能给出上限。由于成 像分析不存在的选择效应,该成像结果表明,Ｇｅｍｉｎｇａ在ＭｅＶ能区仍存在脉冲辐射,虽然Ｇｅｍｉｎｇａ的弱ＭｅＶ辐射使得很难就ＶＰ１数据作时间分析,但仍得到了一     

太阳射电辐射事件与Hα耀斑的相关分析

本文统计了１９９０年１月至８月Ｓ．Ｇ，Ｄ〔１５〕发表的８８００ＭＨｚ太阳射电辐射事件、Ｈα耀斑和软Ｘ射线事件。８８００ＭＨｚ射电事件与耀斑相关率达８３．１％，文章还给出了云南天文台米波射电事件与Ｈα耀斑的统计相关结果，并于Ｂｏｕｌｄｅｒ的结果作了比较，详细分折了它们之间的关系。     

Geminga缺射电脉冲的一种可能机制

应用Ｕｓｏｖ和Ｍｅｌｒｏｓｅγ射线脉冲星的修正的极冠区内间隙模型,得到了γ射线脉冲星Ｇｅｍｉｎｇａ为什么没射电脉冲辐射或射电脉冲辐射很弱的一种可能解释,同时,也可看出,中子星表面的多极场有着重要的作用。     

太阳22周峰年期间2545,2645MHzSpike辐射资料分析

本文简要地讨论了１９９１年１月至１２月太阳峰年期间在２５４５、２６４５ＭＨｚ上观测的５１个Ｓｐｉｋｅ辐射事件的高辐射流量、短持续时间、窄辐射带宽、快速频率漂移、准周期振荡和偏振成份快速变化等观测特征，并对这５１个Ｓｐｉｋｅ事件与光学耀斑活动区磁场强度、磁位形及活动区黑子演化类型的密切关系进行了正、反向统计，鉴于Ｓｐｉｋｅ的辐射的观测特征与统计特征与已知的太阳射电爆发类型和太阳射电成分的特征有很大的     

四颗脉冲星在327MHz频率上的观测

本给出１９９６年１月２２日至２月１日，使用乌鲁木齐南山甚长基线站２５ｍ射电望远望在３２７ＭＨｚ频率上观测脉冲星的部分结果。给出四颗脉冲星的平均脉冲轮廓，脉冲强度和脉冲宽度等重要参数资料。     

利用γ射线数据测量Geminga脉冲星的自行

通过比较不同观测中Ｇｅｍｉｎｇａ脉冲星的γ射线绝对位相，测量出了不同时间Ｇｅｍｉｎｇａ的位置。这些位置表明Ｇｅｍｉｎｇａ自行的赤经分量为０．２２６±０．０３弧秒／年，与它的一个最可能的光学对应体Ｇ″的自行相一致，从而独立地确定了Ｇ″与Ｇｅｍｉｎｇａ之间的对应关系。     

用位相相关方法测量Geminga脉冲星的守时参数

利用γ射线脉冲星Ｇｅｍｉｎｇａ自旋及频率变化的稳定性，采用位相相关的方法分析了ＥＧＲＥＴ对脉冲星Ｇｅｍｉｎｇａ四次观测间隔较长的数据，得到较为准确的守时参数ｆ，位相相关的结果与更长数据段折叠搜索的结果较为接近，对于自旋和频率变化都较为稳定的γ射线脉冲星，位相相关分析方法可以作为提高脉冲星参数精度的有效方法。     

Geomagnetic line spectra-2 to 70 years

Application of a new data adaptive approach to power spectrum estimation has yielded greatly improved knowledge of the geomagnetic spectrum in the range 2 to 70 yr. The first successful line spectrum detection of the solar and double solar cycle variations in absolute geomagnetic element data are presented; also detected are the first four harmonics of the solar cycle and, excepting one, the first nine harmonics of the double solar cycle. Finally, evidence is found for a 60 yr line. The implications of these results for a variety of problems in planetary and space physics are discussed.     

Cross-Correlation of Tenerife Data with Galactic Templates-Evidence for Spinning Dust?

The recent discovery of dust-correlated diffuse microwave emission has prompted two rival explanations: free-free emission and spinning dust grains. We present new detections of this component at 10 and 15 GHz by the switched-beam Tenerife experiment. The data show a turnover in the spectrum and thereby support the spinning dust hypothesis. We also present a significant detection of synchrotron radiation at 10 GHz, which is useful for normalizing foreground contamination of cosmic microwave background experiments at high galactic latitudes.     

Kinematics from spectroscopy with a wide slit: detecting black holes in galaxy centres

We consider long-slit emission-line spectra of galactic nuclei when the slit is wider than the instrumental point spread function, and the target has large velocity gradients. The finite width of the slit generates complex distributions of brightness at a given spatial point in the measured spectrum, which can be misinterpreted as coming from additional physically distinct nuclear components. We illustrate this phenomenon for the case of a thin disc in circular motion around a nuclear black hole (BH). We develop a new method for estimating the mass of the BH that exploits a feature in the spectrum at the outer edge of the BH's sphere of influence, and therefore gives higher sensitivity to BH detection than traditional methods. Moreover, with this method we can determine the BH mass and the inclination of the surrounding disc separately, whereas the traditional approach to BH estimation requires two long-slit spectra to be taken. We show that, with a given spectrograph, the detectability of a BH depends on the sense of rotation of the nuclear disc. We apply our method to estimate the BH mass in M84 from a publicly available spectrum, and recover a value four times lower than that published previously from the same data.     

Development of an Absolute Accelerometer for Extra-Solar Planet Detection

The method of stellar radial velocity variations has recently shown its capability by the first discovery of several extra-solar planets. Accuracies achieved today are in the range 3-10 m/s. The AAA (absolute astronomical accelerometer) is an instrument which aims to reach the photon noise limit for the measurement of velocity changes, with systematic errors of about 1 m/s, long term. The principle is to use a servo-controlled CCD spectrograph as a null detector, and to register always the lines of the star on the same CCD pixels. Thus, systematic errors linked to the Earth-induced large variations are cancelled. A tunable Fabry-Perot channelled spectrum is also following the star spectrum, while the FP thickness is measured by heterodyne detection of the beats between a tunable laser diode and a stabilized laser diode. A complete prototype of the instrument is operating with laboratory sources and the first results are presented. It is planned to use this system with a new spectrograph, to be coupled to the 152 cm telescope at Observatoire de Haute Provence.     

Fast detection of chaotic behavior in galactic potentials

In the present paper we apply a new method of distinction between ordered and chaotic motion in galactic potentials. The method uses the Fourier Transform of a series of time intervals each one representing the time that elapsed between two successive points on the Poincaré surface of section. Examples of the methods ability to achieve an early and clear detection of an orbit's behavior are provided using two galactic potentials. The new method can also be applied in order to have an early distinction between ordered and sticky orbits. The method is generalized in order to be used in models with more than two dimensions. Finally we have tried to find an one‐number index to give us the nature of the orbit instead of checking by eye the whole spectrum. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stabilization of the spectrum position in the main stellar spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences

New results on the stability analysis study of the Main Stellar Spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences when it operated jointly with the CCD detection system on a laboratory source are reported. The spectrum is found to drift along the dispersion direction for several tenths of a pixel (several hundredths of angstrom) over a one-hour time scale. To prevent this drift (i.e., the spectrum shift)—a plane parallel glass plate is mounted; tilt angle of this plate varies as a function of the misalignment between the current and reference spectra of a hollow-cathode tube laboratory source. Operation of the spectrum stabilizer is described. The correction time is of about 1 minute, allowing the position of the spectrum to be maintained to within ±0.0006Å.     

Discovery of co2 ice and leading-trailing spectral asymmetry on the uranian satellite ariel

New 0.8- to 2.4-μm spectral observations of the leading and trailing hemispheres of the uranian satellite Ariel were obtained at IRTF/SpeX during 2002 July 16 and 17 UT. The new spectra reveal contrasts between Ariel’s leading and trailing hemispheres, with the leading hemisphere presenting deeper H₂O ice absorption bands. The observed dichotomy is comparable to leading-trailing spectral asymmetries observed among jovian and saturnian icy satellites. More remarkably, the trailing hemisphere spectrum exhibits three narrow CO₂ ice absorption bands near 2 μm. This discovery of CO₂ ice on one hemisphere of Ariel is its first reported detection in the uranian system.     

Far Ultraviolet Spectrum of Mars

A spectrum of Mars of unprecedented quality was obtained in the range of 904-1183 Å with a spectral resolution of 0.2 Å using the Far Ultraviolet Spectroscopic Explorer. Besides marking the first detection of molecular hydrogen on Mars (Krasnopolsky and Feldman, Science 2001 294, 1914-1917), the spectrum also revealed many emission lines of H, O, N, C, Ar, He, N⁺, C⁺, and Ar⁺ and the bands of N₂ and CO. The spectrum makes it possible to study the emission multiplet structures and the component ratios and to separate many of the blended lines. From the argon lines, we retrieved Ar mixing ratios of 1.5 and 1.3% at 150 and 130 km, respectively, in excellent agreement with the Viking mass spectrometric measurements of 1.6% in the lower atmosphere. The He 584-Å emission observed in second order also agrees with the Extreme Ultraviolet Explorer detection of He on Mars. The observed spectrum may be used as a database to study specific problems such as the dayglow excitation, radiative transfer, and composition in Mars' upper atmosphere.     

The High-Resolution Solar Reference Spectrum between 250 and 550 nm and its Application to Measurements with the Ozone Monitoring Instrument

We have constructed a new high resolution solar reference spectrum in the spectral range between 250 and 550 nm. The primary use of this spectrum is for the calibration of the Dutch – Finnish Ozone Monitoring Instrument (OMI), but other applications are mentioned. The incentive for deriving a new high resolution solar reference spectrum is that available spectra do not meet our requirements on radiometric accuracy or spectral resolution. In this paper we explain the steps involved in constructing the new spectrum, based on available low and high resolution spectra and discuss the main sources of uncertainty. We compare the result with solar measurements obtained with the OMI as well as with other UV-VIS space-borne spectrometers with a similar spectral resolution. We obtain excellent agreement with the OMI measurements, which indicates that both the newly derived solar reference spectrum and our characterization of the OMI instrument are well understood. We also find good agreement with previously published low resolution spectra. The absolute intensity scale, wavelength calibration and representation of the strength of the Fraunhofer lines have been investigated and optimized to obtain the resulting high resolution solar reference spectrum.     

Eigenvector Sky Subtraction

We develop a new method for estimating and removing the spectrum of the sky from deep spectroscopic observations. Our method does not rely on simultaneous measurement of the sky spectrum with the object spectrum. The technique is based on the iterative subtraction of continuum estimates and eigenvector sky models derived from singular value decompositions of sky spectra and sky spectra residuals. Using simulated data derived from small-telescope observations, we demonstrate that the method is effective for faint objects on large telescopes. We discuss simple methods to combine our new technique with the simultaneous measurement of sky to obtain sky subtraction very near the Poisson limit.