海尔—波普彗星的球状喷出物

１９９６年９月观测到海尔－波普彗星的一次喷发,这次喷发持续了几天,在９月１０日和１１日分别观测到慧星的二个球状喷出物,并测得其投影喷出速度约为１００ｍ／ｓ,其后喷出物演变为巨大的喷流。     

海尔—波普彗星球状喷出物的光变曲线

研究了海尔－波普彗星１９９６年９月的光变曲线,发现其在９月１０日至１１日发生了一次爆发,爆发时核Ｖ星等增亮２．１＾ｍ,相应地,在ＣＣＤ图像上也出现爆发时彗核抛出的２个球状凝聚物。     

海尔—波普彗星喷出物的观测

根据上海天台1.56m反射望远镜从1996年2月至1997年5月对海尔－波普彗星跟踪观测所得到的有关喷出物的资料进行了系统的阐述。章根据喷的的不同类型介绍了不同的喷出物－－径向喷流、旋喷流和球状喷出物等的有关数据和观测特征。     

海尔-波普彗星球状喷出物的光变曲线

研究了海尔－波普彗星１９９６年９月的光变曲线,发现其在９月１０日至１１日发生了一次爆发,爆发时核Ｖ星等增亮２．１ｍ．相应地,在ＣＣＤ图像上也发现爆发时彗核抛出的２个球状凝聚物．     

海尔—波普彗星1996年春观测

1996年2月底至3月初，海尔-波普彗星在清晨前重新出现，地平高度较低．本文使用云南天文台1米望远镜加新研制的1024×1024CCD照像机，对该彗星进行了照像观测，精密测定了其位置及光度．结果表明，即使与最新的预报比较起来，仍旧存在着明显的系统偏差．因此，海尔一波普彗星的轨道根数仍需修正．其亮度也比最新的预报稍亮．     

海尔—波普彗星喷流的一次成功检测

上海天文台余山观测站1．56m望远镜于1996年9月23日北京时间19点40分拍摄了海尔-波普彗星的CCD图象。使用的滤光片是R，露光时间为45s。经过偏流（bias）、暗流（dark）以及平场（flat）改正的图象上可以看出彗核附近有5条喷流，但是并不十分清楚（见图1）。这主要是由于喷流叠     

海尔—波普彗星的一个可能的巨大等离子体喷流

１９９６年９月１１日，使用上海天台１．５６ｍ望远镜和Ｓｅｒｉｓ２００ＣＣＤ照相机，在Ｂ波段发现海尔－波普彗星有一个巨大的喷流，初步认定为等离子喷流。     

海尔-波普彗星和α Gem星图象检测结果

利用自行研制的天文视频图象采集系统,对１９９７年５月１日在武定狮山用ＰａｎａｓｏｎｉｓＮＶ－Ｓ８８０ＥＮ型摄像机拍摄的海尔－波普彗星和双子座αＧｅｍ星进行了图象积分处理,并给出检测结果。结果表明：１）经多帧积分处理的海尔－波普彗星图象比单帧图象细节明显的清晰。２）单帧αＧｅｍ星周围淹没在噪声信号中看不到的暗星经多帧叠加后可以“看”到了。     

Narrow-Band Photometry of Comet C/1995 O1 (Hale-Bopp)

Photometric observations of comet C/1995 O1 (Hale-Bopp) carried out at the Stará Lesná Observatory since February to April 1997 are analyzed and discussed. Emission band fluxes and continuum fluxes are presented, from which the total numbers of molecules in the columns of the coma encircled by diaphragms are calculated. The production rates are estimated from the conventional Haser model. We found that the photometric exponent of dust contribution two months prior perihelion was n = 5.2. The photometric exponent n of the cometary magnitude solely to the C₂ emission alone equals 3.3 and that of CN equals 2.5. These values can be explained by a fact that the maximums of production rates of the gases were reached between March 2and 12 and not at the perihelion as it is valid for dust. These results are compared with the values of 1P/Halley (1986 III) under the similar conditions, obtained with the same method and instrument. C/Hale-Bopp exhibited 4.1 times more molecules radiating the CN-emission than 1P/Halley in the same column of the coma. The continuum flux of C/Hale-Bopp was also very strong. The ratios (to 1P/Halley) are 94:1 (Cont. 484.5) and 74:1 (Cont. 365.0). The cometary colour was the same as that of the Sun. This revised version was published online in July 2006 with corrections to the Cover Date.     

CCD Polarimetric Imaging Of Comet Hale-Bopp (C/1995 O1)

Polarimetric observations of the light scattered by dust have been carried out at Pic-du-Midi Observatory with the 2 m telescope in June and September–October 1996, and at Haute-Provence Observatory with the 0.80 m telescope in April 1997. They cover a total number of 11 nights and a large (6.9°–47.7°) phase angle range. The spatial resolution allows to underline structures in the coma, as well in the brightness images as in the polarization maps, with a correlation between the regions of bright structures and the regions of higher polarization. A clear difference appears between the sunward and antisunward side, with higher polarization on the antisunward side. The phase angle coverage allows us to obtain a polarimetric phase curve for the whole coma and to compare it with other cometary phase curves. The degree of polarization is higher for Hale-Bopp than for the comets previously observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Imaging polarimetry of comet Hale-Bopp (C/1995 O1) around perihelion

The polarization distribution of the inner coma of comet Hale-Bopp was measured by CCD imaging around perihelion. The dust shell positions correlate well with relative maxima of polarization. The images taken in the I-band identify different shell systems, each showing individual polarization properties. This could be related to differences in the dust properties of the associated jets. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comet Hale-Bopp (1995 O1)

Considerable interest has been raised by the discovery of Comet Hale-Bopp (1995 O1) and the possibility that it might become a very bright object in Spring 1997. The evidence to support either of the conflicting hypothesis (an intrinsically bright comet or a faint comet in a very large outburst) is too limited to reach solid conclusions and may remain so for some months yet. The pre-discovery observations encountered to date provide some limits to photometric models and suggest that the comet may be intrinsically bright, but do not yet permit a firm discrimination, even between extreme scenarios, due to the enormous extrapolation that must be made from the heliocentric distance at discovery, to that of perihelion.     

Comet Hale-Bopp (C/1995 O1): UVSTAR-FUV Spectroscopy from the Space Shuttle

We report here on unique post-perihelion (2.3 AU) measurements of Comet Hale-Bopp in the FUV-range (950–1250 Å) by means of the UVSTAR spectrometer from the space shuttle with the main purpose of searching for argon and other FUV emitters. New methods for separating the strong airglow emission at shuttle altitudes are here discussed in detail. Due to our low resolution (15 Å) and S/N ratio the possible rocket-borne detection of argon near perihelion (0.9 AU) could not be confirmed. New species as N₂ are suspected but difficult to separate from the strong airglow emission at shuttle altitudes. From the Lyα brightness (1.30± 0.08 kRy) a water production rate Q = 5.9 ± 0.4 × 10²⁹ molecules s^?1 could be derived and compared with other post-perihelion observations.     

Dust Morphology Of The Inner Coma Of C/1995 O1 (Hale-Bopp)

Dust continuum imaging of comet C/1995 O1 (Hale-Bopp) was carried out with the Swedish Vacuum Solar Telescope (SVST)on La Palma in April, 1997. Images were reduced according to standard procedure, aligned, averaged, navigated and enhanced with azimuthal renormalization, rotational derivative, temporal derivative and unsharp masking processing. The rotational period of the nucleus was determined to 11.5 h and the mean projected dust outflow velocity to 0.41 km s⁻¹. Shell envelopes in the sunward side of the coma were separated by a projected distance of ∼15 000–20 000 km and spiralling inwards towards smaller radii in the direction of local evening. Small scale inhomogeneities of size 1 000–2 000 km, interpreted as correlated with variations in dust emission activity, were seen at radii ≤20 000 km. Two overlapping shell systems with a relative lag angle of ∼55° were evident at the time. The north pole of the nucleus was directed towards the Earth. The dust emission pattern is very complex and may be due to several active areas. The shape of the incomplete spiral shell pattern indicates that the angle between the line-of-sight and the rotational axis of the nucleus was not large. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gaseous Jets in Comet Hale-Bopp (1995 O1)

We report the identification of gas jets in comet Hale-Bopp in OH, NH, CN, C₂ and C₃. This is the first time OH and NH jets without an obvious optical dust jet counterpart have been identified in narrowband comet images. We also confirm the existence of CN jets as reported by Larson et al. (1997) and Mueller et al. (1998). Jet features can be seen in the March and April 1997 datasets, approximately a month before and after perihelion. Our results contribute to the understanding of both the chemical properties of the comet as well as the physical mechanisms necessary to produce these features. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dust Morphology Of Comet Hale-Bopp (C/1995 O1): I. Pre-Perihelion Coma Structures In

In 1996 comet Hale-Bopp exhibited a porcupine-like coma with straight jets of dust emission from several active regions on the nucleus. The multi-jet coma geometry developed during the first half of 1996. While the jet orientation remained almost constant over months, the relative intensity of the jets changed with time. By using the embedded fan model of Sekanina and Boehnhardt (1997a) the jet pattern of comet Hale-Bopp in 1996 can be interpreted as boundaries of dust emission cones (fans) from four — possibly five — active regions on the nucleus (for a numerical modelling see part II of the paper by Sekanina and Boehnhardt, 1997b). This revised version was published online in July 2006 with corrections to the Cover Date.     

A CCD Image Archive Of Comet C/1995 O1 (Hale-Bopp): Dust Expansion Velocities

An optical archive of comet Hale-Bopp was obtained over 28 nights from June 1996 to May 1997 covering a range of heliocentric distances of r = 4.12 − 0.91. The CCD images were obtained with the 0.8-m University of Washington Manastash Ridge Observatory and the 0.25-m Pennsylvania State University at Eriemobile observatory. The reduced images clearly document the evolution of features of the coma, which were dominated by radial jetsfrom r = 4.1 − 2.3 AU, curved fan-shaped jets from r = 1.2 − 1.0 AU, and arcs or shells for 0.9 < r < 1.0 AU. We present the images and derive an average dust expansion velocity of V_dust = 0.67 ± 0.07 km s⁻¹ from measurements of the arc features. The images in thearchive will be made available to other researchers for further study. This revised version was published online in July 2006 with corrections to the Cover Date.