The Visual Light Curve Of C/1995 O1 (Hale-Bopp) From Discovery To Late 1997

We present a light curve of C/1995 O1 (Hale-Bopp) compiledfrom more than 3000 visual observations of the comet made by members of the The Astronomer Group world-wide. These observations cover the period from discovery through to the end of 1997. The light curve shows that the rate of brightening of the comet varied widely at different times, with rapid rates of brightening at high heliocentric distance pre-perhelion and a comparably rapid post-perihelion fade. There is no evidence that the comet was suffering a large photometric outburst when first discovered, although a small outburst can be identified at perihelion. At least five difficult brightening regimes can be identified in the light curve between discovery and perihelion. From 2.5 AU to perihelion the rate of brightening with decreasing heliocentric distance was typical for “fairly” new comets(n ∼ 3.5, where “n” is the power law exponent of the heliocentric distance), although this was preceded by a period of very slow brightening with n ∼ 1 from r ∼ 4.0 AU to r ∼ 2.8 AU and followed by an initially more rapid brightening which appears to be related to the on-set of rapid water sublimation activity. We derive the light curve parameters at different stages of the comet's apparition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gain calibration of CCD systems at VBO

The system gain of two CCD systems in regular use at the Vainu Bappu Observatory, Kavalur, is determined at a few gain settings. The procedure used for the determination of system gain and base-level noise is described in detail. The Photometrics CCD system at the 1-m reflector uses a Thomson-CSF TH 7882 CDA chip coated for increased ultraviolet sensitivity. The gain is programme-selected through the parameter ‘cgain’ varying between 0 and 4095 in steps of 1. The inverse system gain for this system varies almost linearly from 27.7 electrons DN^-1 at cgain = 0 to 1.5 electrons DN^-1 at cgain = 500. The readout noise is ≲ 11 electrons at cgain = 66. The Astromed CCD system at 2.3-m Vainu Bappu Telescope uses a GEC P8603 chip which is also coated for enhanced ultraviolet sensitivity. The amplifier gain is selected in discrete steps using switches in the controller. The inverse system gain is 4.15 electrons DN^-1 at the gain setting of 9.2, and the readout noise ∼ 8 electrons.     

The Herbig Ae/Be Star V586 Ori

Studies of the Herbig Ae/Be star V586 Ori based on photoelectric observations in the Strömgren system are reported. It is found that as the brightness decreases, the Balmer discontinuity index initially increases and then begins to drop. As the star fades, the index decreases. We have previously found similar variations in the indices and C for UX Ori, RR Tau, and V351 Ori. It is shown that V586 Ori has the characteristics of a shell-star.     

西藏班公湖-怒江结合带北缘多龙地区侏罗纪 增生杂岩的特征及意义

提出遥感图像地质解译三维可视化及影像动态分析新方法,综合利用3S技术,遥感图像数字处理技术,虚拟现实和全数字摄影测量等高科技,通过遥感图像的正射影像处理,多类型遥感图像数据融合,高精度DEM生成和影像复合等工序,按照一定比例尺和飞行路线生成测区的虚拟三维影像动画系列图,以解决高原区数字区调工作者面临的实际问题,弥补其不足。     

On the shape of elliptical galaxies

We propose a test for the existence of prolate elliptical galaxies based on the properties of the photometric parameters introduced in the Córdoba surface photometry.     

Observations of flat-spectrum radio sources at λ850 μm from the James Clerk Maxwell Telescope – I. 1997 April to 2000 April

Calibrated data for 65 flat-spectrum extragalactic radio sources are presented at a wavelength of 850 μm, covering a three-year period from 1997 April. The data, obtained from the James Clerk Maxwell Telescope using the SCUBA camera in pointing mode, were analysed using an automated pipeline process based on the Observatory Reduction and Acquisition Control–Data Reduction ( orac–dr ) system. This paper describes the techniques used to analyse and calibrate the data, and presents the data base of results along with a representative sample of the better-sampled light curves.     

盾牌座δ型变星金牛座θ~2的新光电测光

本文给出在北京天文台兴隆观测站获得的盾牌座δ型变星金牛座θ~2的新光电测光资料,它们是新近开展的一次多台站国际联合观测的一部分。以前得到的四频率解(文[1])与新资料符合得极好。单次测量的残差约±0.003星等。     

The bolometric light curve of SN 1993J and the nature of its progenitor

We have constructed the bolometric light curve of SN 1993J based on UBVRI(JHK) photometric data obtained from various sources and assumingA _V = 0 and a distance modulus of 27.6. Effective temperatures and photosphere radius at various times have been obtained from detailed blackbody fits. The bolometric light curve shows two maxima. The short rise time to the second maximum, and the luminosities at the minimum and the second maximum are used to constrain the properties of the progenitor star. The total mass of the hydrogen envelope M_H, in the star is found to be ≲ 0.2 M_⊙ at the time of explosion, and the explosion ejected about 0.05 M_⊙ of Ni⁵⁶. Thin hydrogen envelope combined with a sufficient presupernova luminosity suggest that the exploding star was in a binary with a probable period range of 5yr ≤P _orb ≤ 11yr.