云南天文台1m望远镜暗天体分光仪和照相机

云南天文台1m望远镜终端之一的暗天体分光仪和照相机具有4种运行模式:缩焦照相机、无缝多目标光谱仪、有缝光谱仪和星冕仪。这4种运行模式能在几分钟的时间内相互转换,高效快速和灵活方便。该仪器的光学质量优秀,光学系统消像差,特别是消色差。由于光学系统消色差,所成像的低色散光谱在404.6～766.5nm全波段尖锐平直。在多色测光时,各测光波段的像面位置不变,同时兼有大视场的优点,可提高测光精度和测光效率。     

Stray light analysis of the Xinglong 2.16-m telescope

An effort towards understanding the problems associated with stray light related to the Xinglong2.16-m telescope is presented to estimate the stray light performance of the telescope itself and provide a method for improving stray light suppression. Stray light analysis for the 2.16-m telescope model, which consists of an onion shaped dome, telescope structure, equatorial mount and telescope optics, has been developed in two cases(1) pointing to 60?and(2) pointing to zenith, in both azimuth and elevation directions.The Point Source Normalized Irradiance Transmittance(PSNIT), which is generally used for assessing stray light and is uncorrelated to entrance aperture, is calculated with a series of off-axis angles. It shows that the PSNIT values are less than 10~(-7) when off-axis angles are larger than ±20?. The dominant contributors to stray light(primary and secondary mirror, telescope structure and dome) are identified to guide performance improvement. The analyses indicate that significant benefit can be realized by adding only five vanes inside the bottom portion of the secondary baffle. In the case of pointing to zenith, the PSNIT values will decrease about 40% on average.     

Surface studies of asteroids with the Faint Object Camera of the Space Telescope

Minor planets have been observed in the last few years for physical properties using photometry, polarimetry and IR-radiometry. Using the Faint Object Camera (FOC) of the Space Telescope (ST) it will be possible for the first time to observe a large number of asteroids with direct imaging systems.We propose to use the FOC with high resolution mode to examine minor planets with respect to (a) diameters and shapes, (b) surface and detail studies, (c) densities and (d) possible binary nature of selected asteroids.Paper presented at the European Workshop on Planetary Sciences, organised by the Laboratorio di Astrofisica Spaziale di Frascati, and held between April 23–27, 1979, at the Accademia Nazionale del Lincei in Rome, Italy.     

High resolution imaging of Pluto and Charon with the Faint Object Camera of the Hubble Space Telescope

Images of the Pluto-Charon system were obtained with the Faint Object Camera (FOC) of the Hubble Space Telescope (HST) with the aim of determination of radii, fluxes, and albedos. The resolution of the already diffraction limited images was further improved by image restoration, yielding indications of surface albedo distributions which are qualitatively consistent with models derived from observations of Pluto-Charon mutual eclipses.Based on Observations with the NASA-ESA Hubble Space Telescope, which is operated by AURA, Inc., under NASA contract NAS 5-26555.     

Observations of the supernova SN1987L with the new Faint Object Spectrograph on the 4.2 m William Herschel Telescope

We present the spectrum of the supernova SN1987L in NGC 2336 over the wavelength range 4000–9700 Å as recorded in one 500 s exposure on 20–21 October, 1987. This spectrum was taken using the new Faint Object Spectrograph on the 4.2 m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos.We conclude that SN1987L was a type Ia supernova, and approximately 100 days post maximum at the time of the observation.     

Metallicity and star formation activities of the interacting system Arp 86 from observations with MOS on the Xinglong 2.16m telescope

We present an analysis of the metallicity and star formation activities of H II regions in the interacting system Arp 86, based on the first scientific observations using multi-object spectroscopy with the 2.16 m telescope at the Xinglong Observing Station. We find that the oxygen abundance gradient in Arp 86 is flatter than that in normal disk galaxies, which confirms that gas inflows caused by tidal forces during encounters can flatten the metallicity distributions in galaxies. The companion galaxy NGC 7752 is currently experiencing a galaxy-wide starburst with a higher star formation rate surface density than the main galaxy NGC 7753, which can be explained in that the companion galaxy is more susceptible to the effects of interaction than the primary. We also find that the galaxy 2MASX J23470758+2926531 has similar abundance and star formation properties to NGC 7753, and may be a part of the Arp 86 system.     

北京天文台兴隆观测站夜天光光谱证认

介绍了夜天光光谱的观测方法,给出了北京天文台兴隆观测站５３０ｎｍ－８２０ｎｍ的夜天光发射光谱,并对它们进行了证认,测定了大气辉光线的夜变化;光谱中城市灯光线ＮａＩ和ＨｇＩ均较弱,表明兴隆站目前的光污染尚不严重．     

兴隆80cm TNT望远镜测光性能的研究

对兴隆80cm TNT望远镜CCD系统进行了测试和研究.观测了大批Landolt标准星定出了UBVRI宽带滤光片的星等系统转换关系,重点讨论了白光与R滤光片之间的关系,结果表明该系统与标准Johnson系统很接近,白光与R滤光片之间也比较接近.同时测定了兴隆站的夜天光.     

Multitemporal observations of identical active dust devils on Mars with the High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC)

Active dust devils were observed in Syria Planum in Mars Observer Camera - Wide Angle (MOC-WA) and High Resolution Stereo Camera (HRSC) imagery acquired on the same day with a time delay of ∼26 min. The unique operating technique of the HRSC allowed the measurement of the traverse velocities and directions of motion. Large dust devils observed in the HRSC image could be retraced to their counterparts in the earlier acquired MOC-WA image. Minimum lifetimes of three large (avg. ∼700 m in diameter) dust devils are ∼26 min, as inferred from retracing. For one of these large dust devil (∼820 m in diameter) it was possible to calculate a minimum lifetime of ∼74 min based on the measured horizontal speed and the length of its associated dust devil track. The comparison of our minimum lifetimes with previous published results of minimum and average lifetimes of small (∼19 m in diameter, avg. min. lifetime of ∼2.83 min) and medium (∼185 m in diameter, avg. min. lifetime of ∼13 min) dust devils imply that larger dust devils on Mars are active for much longer periods of time than smaller ones, as it is the case for terrestrial dust devils. Knowledge of martian dust devil lifetimes is an important parameter for the calculation of dust lifting rates. Estimates of the contribution of large dust devils (>300-1000 m in diameter) indicate that they may contribute, at least regionally, to ∼50% of dust entrainment by dust devils into the atmosphere compared to the dust devils <300 m in diameter given that the size-frequency distribution follows a power-law. Although large dust devils occur relatively rarely and the sediment fluxes are probably lower compared to smaller dust devils, their contribution to the background dust opacity by dust devils on Mars could be at least regionally large due to their longer lifetimes and ability of dust lifting into high atmospheric layers.     

Observations of Comet C/2001 A2 (Linear) with the Multipupil Fiber Spectrograph

We present preliminary results of observations of the spectrum of comet C/2001 A2(LINEAR) obtained with the Multipupil Fiber Spectrograph, installed in the PrimeFocus of the 6-m Telescope of the SAO of the RAS (Northern Caucasus, NizhnyArkhyz), on August 11/12, 12/13 and 14/15, 2001. High resolution spectra of thecomet were obtained in the range from 3800–5200 AA. The emission lines in the spectrum of comet C/2001 A2 (LINEAR) on Aug. 12, 2001 were identified. Thefluorescent continuum in the spectrum of comet C/2001 A2 (LINEAR) on Aug. 12,2001 is detected.     

Spectral Diagnostics of an Active Region Observed by the Solar EUV Rocket Telescope and Spectrograph (SERTS)

The EUV spectrum of a solar active region observed by SERTS-89 is used to estimate physical parameters such as electron density, elemental abundance and inhomogeneity in the emitting source. A total of 13 ions, namely, Neiv-vi, Mgv-ix, Sivii-x and Sx, are studied in the SERTS spectral range 170-450 Ú, providing plasma diagnostics at temperatures between10₅ –10⁶ K. Attention is called to results derived from ion pairs of different elements that are formed over similar temperature regimes, which allow special checks on the standard assumptions of spectral analyses. Some EUV lines, not originally reported in the SERTS-89 spectrum, are shown to have measureable intensities and are indicated for future observations.     

The Cassini Campaign observations of the Jupiter aurora by the Ultraviolet Imaging Spectrograph and the Space Telescope Imaging Spectrograph

We have analyzed the Cassini Ultraviolet Imaging Spectrometer (UVIS) observations of the Jupiter aurora with an auroral atmosphere two-stream electron transport code. The observations of Jupiter by UVIS took place during the Cassini Campaign. The Cassini Campaign included support spectral and imaging observations by the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). A major result for the UVIS observations was the identification of a large color variation between the far ultraviolet (FUV: 1100-1700 Å) and extreme ultraviolet (EUV: 800-1100 Å) spectral regions. This change probably occurs because of a large variation in the ratio of the soft electron flux (10-3000 eV) responsible for the EUV aurora to the hard electron flux (∼15-22 keV) responsible for the FUV aurora. On the basis of this result a new color ratio for integrated intensities for EUV and FUV was defined (4πI1550-1620 Å/4πI1030-1150 Å) which varied by approximately a factor of 6. The FUV color ratio (4πI1550-1620 Å/4πI1230-1300 Å) was more stable with a variation of less than 50% for the observations studied. The medium resolution (0.9 Å FWHM, G140M grating) FUV observations (1295-1345 Å and 1495-1540 Å) by STIS on 13 January 2001, on the other hand, were analyzed by a spectral modeling technique using a recently developed high-spectral resolution model for the electron-excited H₂ rotational lines. The STIS FUV data were analyzed with a model that considered the Lyman band spectrum (B ) as composed of an allowed direct excitation component (X ) and an optically forbidden component (X followed by the cascade transition ). The medium-resolution spectral regions for the Jupiter aurora were carefully chosen to emphasize the cascade component. The ratio of the two components is a direct measurement of the mean secondary electron energy of the aurora. The mean secondary electron energy of the aurora varies between 50 and 200 eV for the polar cap, limb and auroral oval observations. We examine a long time base of Galileo Ultraviolet Spectrometer color ratios from the standard mission (1996-1998) and compare them to Cassini UVIS, HST, and International Ultraviolet Explorer (IUE) observations.     

Si IX Emission Lines in Spectra Obtained with the Solar euv Research Telescope and Spectrograph (Serts)

Theoretical electron-density-sensitive emission line ratios involving 2s ²2p ²–2s2p ³ transitions in Si?ix between 223 and 350 Å are presented. A comparison of these with an extensive dataset of solar-active-region, quiet-Sun, subflare and off-limb observations, obtained during rocket flights by the Solar EUV Research Telescope and Spectrograph (SERTS), reveals generally very good agreement between theory and experiment. This provides support for the accuracy of the line-ratio diagnostics, and hence the atomic data on which they are based. In particular, the density-sensitive intensity ratio I(258.10 Å)/I(349.87 Å) offers an especially promising diagnostic for studies of coronal plasmas, as it involves two reasonably strong emission lines and varies by more than an order of magnitude over the useful density range of 10⁹–10¹¹ cm^?3. The 2s ²2p ^2 1 S ₀–2s2p ^3 1 P ₁ transition at 259.77 Å is very marginally identified for the first time in the SERTS database, although it has previously been detected in solar flare observations.

     

Si x emission lines in spectra obtained with the Solar EUV Rocket Telescope and Spectrograph (SERTS)

New R -matrix calculations of electron impact excitation rates for transitions among the 2s²2p, 2s2p² and 2p³ levels of Si  x are presented. These data are subsequently used, in conjunction with recent estimates for proton excitation rates, to derive theoretical electron density sensitive emission-line ratios involving transitions in the ∼253–356 Å wavelength range. A comparision of these with observations of a solar active region and subflare, obtained during the 1989 flight of the Solar EUV Rocket Telescope and Spectrograph ( SERTS ), reveals that the electron densities determined from most of the Si  x line ratios are consistent with one another for both solar features. In addition, the derived densities are also in good agreement with the values of N _e estimated from diagnostic lines in other species formed at similar electron temperatures to Si  x , such as Fe  xii and Fe  xiii . These results provide observational support for the general accuracy of the adopted atomic data, and hence line ratio calculations, employed in the present analysis. However, we find that the Si  x 256.32-Å line is blended with the He  ii transition at the same wavelength, while the feature at 292.25 Å is not due to Si  x , but currently remains unidentified. The intensity of the 253.81-Å line in the SERTS active region spectrum is about a factor of 3 larger than expected from theory, but the reason for this is unclear, and requires additional observations to explain the discrepancy.     

S xi Emission Lines in Active Region Spectra Obtained with the Solar euv Rocket Telescope and Spectrograph (Serts)

Theoretical electron density sensitive emission line ratios involving a total of eleven 2s ²2p ²–2s2p ³ transitions in Sxi between 187 and 292 Å are presented. A comparison of these with solar active region observations obtained during rocket flights by the Solar EUV Rocket Telescope and Spectrograph (SERTS) reveals generally good agreement between theory and experiment. However, the 186.87 Å line is masked by fairly strong Fexii emission at the same wavelength, while 239.83 Å is blended with an unknown feature, and 285.58 Å is blended with possibly Niv 285.56 Å. In addition, the 191.23 Å line appears to be more seriously blended with an Fexiii feature than previously believed. The presence of several new Sxi lines is confirmed in the SERTS spectra, at wavelengths of 188.66, 247.14 and 291.59 Å, in excellent agreement with laboratory measurements. In particular, the detection of the 2s ²2p ^{2 3} P ₁ –2s2p ^{3 3} P _0,1 transitions at 242.91 Å is the first time (to our knowledge) that this feature has been identified in the solar spectrum. The potential usefulness of the Sxi line ratios as electron density diagnostics for the solar transition region and corona is briefly discussed.     

Mgix emission lines in an active region spectrum obtained with the Solar EUV Rocket Telescope and Spectrograph (SERTS)

Theoretical electron-temperature-sensitive Mgix emission line ratios are presented forR _I =I(443.96 )/I(368.06 ),R ₂ =I(439.17 )/I(368.06 ),R ₃ =I(443.37 )/I(368.06 ),R ₄ =I(441.22 )/I(368.06 ), andR ₅ =I(448.28 )/I(368.06 ). A comparison of these with observational data for a solar active region, obtained during a rocket flight by the Solar EUV Rocket Telescope and Spectrograph (SERTS), reveals excellent agreement between theory and observation forR ₁ throughR ₄, with discrepancies that average only 9%. This provides experimental support for the accuracy of the atomic data adopted in the line ratio calculations, and also resolves discrepancies found previously when the theoretical results were compared with solar data from the S082A instrument on boardSkylab. However in the case ofR ₅, the theoretical and observed ratios differ by almost a factor of 2. This may be due to the measured intensity of the 448.28 line being seriously affected by instrumental effects, as it lies very close to the long wavelength edge of the SERTS spectral coverage (235.46–448.76 ).