高精度恒星孔径测光注释

详细介绍了利用孔径测光方法得到CCD图像中恒星仪器星等的全过程,以及使用自己设计的程序对云南天文台1m望远镜观测的CCD图像进行实际测量的实验。测量结果表明:对亮星(约10mag)的内部测量精度能达到0.003mag,而对暗星(约17mag)达到0.2mag。同时,对相关问题进行深入讨论,总结了一些实验所得的经验,并与测光软件IRAF进行了内部精度的比较。     

吉林280mm全天区可转动光电阵测光精度评估研究

位于吉林天文观测基地的280 mm全天区可转动光电阵是一台用于空间碎片巡天观测的设备。为了研究该设备的光度测量性能,评估其测光精度,选择M67疏散星团中的测光标准星进行观测。首先,在IRAF(Image Reduction and Analysis Facility)中对观测图像进行预处理,之后进行较差测光;接着,提取测光数据并将整晚观测数据进行最小二乘直线拟合,拟合结果给出了主消光系数及相应的系统转换系数,并得到仪器星等至标准星等的转换公式;最后,利用计算得到的均方根误差对设备的测光精度进行大致评估。计算结果表明,在标准测光夜测量亮于13.8 mag时,280 mm全天区可转动光电阵的测光精度可达0.13 mag。同时将观测图像与UCAC2星表匹配识别,利用背景恒星中的UCAC2标准星做外符合精度的校验,结果与前者基本相同。本设备的测光精度基本满足空间碎片巡天观测的要求。     

基于Python的自动测光程序设计与实现

本文基于Python设计和实现自动测光程序。首先扫描文件名实现文件分类;然后进行数据检查、预处理与孔径测光,并保存测光数据;最终由观测者指定目标星与比较星,程序从测光结果中提取相应星等与观测时间等数据,获得基于较差测光法的光变曲线。为解决数据提取中星图匹配问题,提出自动追踪移动目标的基于向量特征星图匹配算法,能自动匹配偏移较大的星图,并跟踪不断移动的小行星。使用本程序分别处理双星和小行星观测数据,并与IRAF(Image Reducation and Analysis Facility)测光结果比较,测光结果最大偏差分别为0.04 mag和0.043 mag,标准偏差分别为±0.005 mag和±0.007 mag。     

基于有效点扩散函数的高精度测光

介绍了利用有效点扩散函数拟合方法得到CCD图像中恒星仪器星等的过程。对国家天文台1 m望远镜观测的16幅CCD图像进行实际测量,结果表明:亮星的内部测量平均精度为0.015 mag,最高精度可达0.001 5 mag,而暗星则达到0.043 mag。与Gauss拟合测光方法相比平均精度提高了3倍多,精度标准偏差是0.005,说明该测量方法比较稳定,是一种更优的测光方法。     

2.4米望远镜主镜镀膜工艺的研究

利用国内首个自上向下热蒸发反射膜的大型镀膜机ZZS3200,开展了2.4 m望远镜主镜镀膜工艺的研究。从镀膜的环境控制,镀膜机蒸发源布置,保护膜的选择,旧膜脱膜等方面出发,探索一种适合2.4 m望远镜主镜的镀膜工艺流程,并依此完成2.4 m望远镜主镜镀带MgF2保护的铝反射膜工作。陪镀片检测表明,铝膜膜厚极大极小值差43 nm,主镜反射膜在350~1 100 nm范围内平均反射率87.16%,经2.4 m望远镜实测,镀膜完成后极限星等不低于23.5 mag,比镀膜前约提高1 mag。2013年12月17日,在2.4 m望远镜上,利用终端云南天文台暗弱天体分光及成像仪(Yunnan Faint-Object Spectrograph and Camera,YFOSC),使用棱栅Grism3分光,对超新星SN 2011fe(V波段19.5 mag)成功进行光谱观测。30 min单幅曝光,获得暗于19 mag天体的光谱,刷新了该类天体在国内观测的新的记录。该目标在光谱观测的同时有相应的测光数据以及测光标准星观测,因此星等测量误差小于0.1 mag,可以用于定量分析。     

IRAF软件在Blazars天体中的CCD测光自动数据处理研究

针对IRAF软件在绝对测光法观测Blazars天体CCD测光中的应用,开发了一套自动数据处理的程序.该程序可以减少人为误操作的干扰,使观测结果更为稳定,提高了数据处理的效率.同时,在长期研究和使用IRAF软件的基础上,给出了我们应用IRAF软件在CCD测光中的一些研究结果,并对在Redhat Linux中的自动测光过程进行了总结.     

关于提高恒星三角视差测定精度的研究

利用佘山40cm折射望远镜拍摄的BD＋70°68、BD＋63°869和BD＋2°348三颗星的底片进行了视差解算，根据归算所得结果，对如何提高恒星三解视差测定值的精度和有关观测、测量、归算中的一些具体问题进行了分析和讨论，这些问题包括观测历元的安排、时角的限制、露光量的掌握、参考星的选择、归算模型的确定等。并且，本文还初步估计了上海天文台1.56m反射望远镜测定恒星三角视差可能达到的外部精度。     

空间碎片观测中拖长星像的测光

提出空间碎片观测中对拖长背景恒星的测光算法,介绍了该方法的基本原理.利用迭代法对目标图像进行局部阈值分割提取,得到的二值图像通常包含多个连通域.最后对各连通域块检测判断,计算出目标的星等,达到测光的目的.通过与天文图像和数据处理软件IRAF的测光结果对比,此算法的误差在0.02mag左右,可以达到测光的要求.     

球状星团NGC4147天区115颗恒星的绝对自行和BVRI测光

以上海天台佘山40cm折射望远镜于1958年拍摄的3张照相底片为第一期资料,印度Kavalur的2.34m Vainu Bappu望远镜于1996年用CCD拍摄的4幅图象为第二期资料,使用Brosche等人1985年发表的球状星团NGC4147天区42颗恒星的位置和绝对自行作为参考架,用中心重叠法进行天体测量归算,得到了这个星团中心附近11'×11'天区内到B＝17.6mag为止115颗恒星的位置和绝对自行,并利用这些自行对成员概率作了估计,同时,还用Vainu Bappu望远镜的CCD进行了BVRI四色测光。本给出了这115颗恒星的位置、绝对自行和成员概率数据,同时,还给出了用Vainu Bappu望远镜的CCD获得的这些恒星的BVRI测光数据。     

Blazar短时标光变的孔径测光分析

对IRAF软件包处理AGN观测数据中,测光孔径、背景环的内外径差、背景等参数选取对测光结果的影响进行了实测比较.结果表明孔径的选取对测光结果的影响较大,而背景环的内外径差参数的影响不大;对所处理的观测序列中,背景参数对测光结果没有影响.对Blazar短时标光变监测中由于比较星选择引起的修正因子Γ进行了讨论,并对在2007年3月观测的PKS1510-089和OJ248数据进行了计算和比较分析.     

Searching for the brightest stars in galaxies outside the Local Group

This paper introduces a technique for searching for bright massive stars in galaxies beyond the Local Group.To search for massive stars,we processed the results of stellar photometry from the Hubble Space Telescope(HST) images using the DAOPHOT and DOLPHOT packages.The results of such searches are demonstrated with examples of the galaxies DDO 68,M94 and NGC 1672.In the galaxy DDO 68,the LBV star changes its brightness,and massive stars in M94 can be identified by excess in the Ha band.For the galaxy NGC 1672,we measure the distance for the first time by the TRGB method,which enabled determining the luminosities of the brightest stars,likely hypergiants,in the young star formation region.So far,we have performed stellar photometry on HST images of 320 northern sky galaxies located at a distance less than 12 Mpc.This allowed us to identify 53 galaxies with probable hypergiants.Further photometric and spectral observations of these galaxies are planned to search for massive stars.     

MDia and POTS

We describe the Munich Difference Imaging Analysis pipeline that we developed and implemented in the framework of the Astro-WISE¹ package to automatically measure high precision light curves of a large number of stellar objects using the difference imaging approach. Combined with programs to detect time variability, this software can be used to search for planetary systems or binary stars with the transit method and for variable stars of different kinds. As a first scientific application, we discuss the data reduction and analysis performed with Astro-WISE on the pre-OmegaTranS data set, that we collected during a monitoring campaign of a dense stellar field with the Wide Field Imager at the ESO 2.2 m telescope.     

A search for previously unrecognized metal-poor subdwarfs in the Hipparcos astrometric catalogue

We have identified 317 stars included in the Hipparcos astrometric catalogue that have parallaxes measured to a precision of better than 15 per cent, and the location of which in the ( M _V ,( B − V ) _T ) diagram implies a metallicity comparable to or less than that of the intermediate-abundance globular cluster M5. We have undertaken an extensive literature search to locate Strömgren, Johnson/Cousins and Walraven photometry for over 120 stars. In addition, we present new UBV ( RI )_C photometry of 201 of these candidate halo stars, together with similar data for a further 14 known metal-poor subdwarfs. These observations provide the first extensive data set of R _C I _C photometry of metal-poor, main-sequence stars with well-determined trigonometric parallaxes. Finally, we have obtained intermediate-resolution optical spectroscopy of 175 stars.
47 stars still lack sufficient supplementary observations for population classification; however, we are able to estimate abundances for 270 stars, or over 80 per cent of the sample. The overwhelming majority have near-solar abundance, with their inclusion in the present sample stemming from errors in the colours listed in the Hipparcos catalogue. Only 44 stars show consistent evidence of abundances below [Fe/H]=−1.0 . Nine are additions to the small sample of metal-poor subdwarfs with accurate photometry. We consider briefly the implication of these results for cluster main-sequence fitting.     

Field optimization and CCD data simulation for the antarctic International Concordia Explorer Telescope (ICE‐T)

We performed extensive data simulations for the planned ultra‐wide‐field, high‐precision photometric telescope ICE‐T (International Concordia Explorer Telescope). ICE‐T consists of two 60 cm‐aperture Schmidt telescopes with a joint field of view simultaneously in two photometric bandpasses. Two CCD cameras, each with a single 10.3k × 10.3k thinned back‐illuminated device, would image a sky field of 65 square degrees. Given a location of the telescope at Dome C on the East Antarctic Plateau, we searched for the star fields that best exploit the technical capabilities of the instrument and the site. We considered the effects of diurnal air mass and refraction variations, solar and lunar interference, interstellar absorption, overexposing of bright stars and ghosts, crowding by background stars, and the ratio of dwarf to giant stars in the field. Using NOMAD, SSA, Tycho‐2 and 2MASS‐based stellar positions and BVIJH magnitudes for these fields, we simulated the effects of the telescope's point‐spread‐function, the integration, and the co‐addition times. Simulations of transit light curves are presented for the selected star fields and convolved with the expected instrumental characteristics. For the brightest stars, we showed that ICE‐T should be capable of detecting a 2 R_Earth Super Earth around a G2 solar‐type star, as well as an Earth around an M0‐star – if these targets were as abundant as hot Jupiters. Simultaneously, the telescope would monitor the host star's surface activity in an astrophysically interpretable manner (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

银河系铝元素丰度研究

恒星的Al元素丰度可以为探索星团和星系的化学演化提供重要线索.通过系统分析银河系薄盘、厚盘、核球、银晕以及M4、M5等球状星团中恒星的[Al/Fe]随恒星金属丰度[Fe/H]的变化趋势,得出银河系薄盘、厚盘和核球恒星的[Al/Fe]随着[Fe/H]的增加而缓慢下降,而球状星团M4和M5恒星的[Al/Fe]随[Fe/H]增加没有下降趋势,这暗示Ia超新星对M4和M5恒星元素丰度的贡献比较小.详细研究了银河系恒星[Al/Fe]与[Mg/Fe]、[Na/Fe]的相关性,结果表明银河系场星的[Al/Fe]与[Mg/Fe]正相关,但在球状星团M4和M5恒星中未见此相关性;银河系盘星及M4和M5等球状星团恒星的[Al/Fe]与[Na/Fe]都存在正相关.     

Positional and photometric CCD observations of the comet Shoemaker-Levy 9

Positional and photometric CCD observations of the comet Shoemaker-Levy 9 fragments were carried out at the Abastumani Astrophysical Observatory. Up to 15 named fragments were detected and their equatorial coordinates and magnitudes are reported. CCD frames were processed using DAOPHOT II. The internal precision of reference star positions down to 18^m is 0.″7 and the mean error of photometry does not exceed ±0.3 mag.     

疏散星团M67成员星的两点相关分析

对著名老年疏散星团M67的成员星进行了两点相关函数分析,讨论了团星的空间分布情况及质量分层现象.结果表明:M67成员星的两点相关函数能很好地用幂律形式来描述,其成员星在空间分布上具有显著的成团性和自相似性.对M67不同光度成员星两点自相关函数的分析表明,亮星相比暗星具有更强的相关强度和更大的相关指数,说明在星团内部出现了明显的空间质量分层现象,亮星比暗星具有更强的成团性和更大的中心聚度.不同光度成员星间两点交叉相关函数的分析进一步表明,不同光度成员星之间并没有表现出绝对的空间质量分层现象,亮星和暗星在空间分布上相互交织、相互渗透.     

CCD photometry of BM Orionis and other trapezium stars

New light curves have been obtained for the eclipsing binary BM Orionis in theuvbyRI filter regions. The observations were made from 1988 to 1990 using the CCD photometer of the Behlen Observatory of the University of Nebraska. Reduction of all image data to magnitudes for BM Orionis and for each of the five other brightest stars in the ¹ Orionis group known as the Trapezium was accomplished by use of Stetson's DAOPHOT crowded-field photometry program. Differential magnitudes and light curves for BM Orionis and V1016 Orionis have been constructed using star D of the group as the primary comparison star. Possible indications of variability have also been looked for in the member stars C, E, and F with negative results for stars C and F and positive results for star E. The same CCD frames also contained the stars ² Orionis A and B. A light curve of the possibly-eclipsing spectroscopic binary ² Orionis A folded on its spectroscopic period does show some variability, but no obvious eclipses.     

Multisite campaign on the open cluster M67 – I. Observations and photometric reductions

We report on an ambitious multisite campaign aimed at detecting stellar variability, particularly solar-like oscillations, in the red giant stars in the open cluster M67 (NGC 2682). During the six-week observing run, which comprised 164 telescope nights, we used nine 0.6-m to 2.1-m class telescopes located around the world to obtain uninterrupted time series photometry. We outline here the data acquisition and reduction, with emphasis on the optimization of the signal-to-noise ratio of the low-amplitude (50–500 μmag) solar-like oscillations. This includes a new and efficient method for obtaining the linearity profile of the CCD response at ultrahigh precision (∼10 parts per million). The noise in the final time series is 0.50 mmag per minute integration for the best site, while the noise in the Fourier spectrum of all sites combined is 20 μmag. In addition to the red giant stars, this data set proves to be very valuable for studying high-amplitude variable stars such as eclipsing binaries, W UMa systems and δ Scuti stars.     

LBV Candidates in M31 and M33. Overview of 20 Years of the 6-m Telescope: Observations and Results

An ongoing SAO RAS program for the 6-m telescope to search for and study luminous blue variable (LBV) candidates in the M31 and M33 galaxies was started in 1997. This paper summarizes the results of our observations over the last 20 years. Over this time, we have a general lists of candidates and obtained photometry and spectroscopy for approximately one hundred stars from the list. A detailed study and classification of LBV candidates were carried out.We alsomonitored spectrally and photometrically the confirmed LBV stars in these galaxies. Based on these results, the spectral energy distributions (SEDs) of LBVs and LBV candidates were computed, and the interstellar extinction values, temperature, and luminosity were derived. We propose a new method of confirming the nature of LBV stars. It is based on a special property exhibited only by LBV stars—the constancy of the bolometric luminosity, with except of a rare phase of giant eruption, registered for two historical LBVs in our galaxy and about few dozen extragalactic LBVs. Using this method, we determine the fundamental parameters of these stars: temperature, radius, luminosity, and interstellar extinction. We discuss the nature of several individual LBV stars discovered by us in M33 and the classification of the LBV candidates in M31. Thus, for 20 years of observations we have found four LBV stars in M33; in the M31 galaxy with different methods, we have confirmed seven objects as a LBV class.