THREE EVENTS OF OUTBURST OF COMET HALE-BOPP

The results of photographic observations of Comet Hale-Bopp made at Qingdao Station of Purple Mountain Observatory during the period from September to November of 1996 are given. It is shown that three events of outburst occurred on Sept. 24, Oct. 26 and Nov. 13, and a large jet appeared in the plate of Sept.23,1996.     

Chemical Processes in Cometary Comae

Recent developments in the chemical modelling of cometary comae aredescribed. We discuss the cyanide chemistry and present new HCNobservations of the recent comet C/2002 C1 (Ikeya–Zhang). Theconnection between interstellar and cometary organic molecules isdiscussed from the perspective of recent theories of interstellargas-grain chemistry.     

The Spin Axis Position of C/1995 O1 (Hale–Bopp)

Monitoring of the near-nucleus activity of C/1995 O1 (Hale-Bopp) began in Teide Observatory in August 1995. During 1996 the comet was observed on 72 nights between March 26 and November 13. A permanent fan structure was observed towards the north during the whole period of observation. The position angle of the axis of this fan was measured and its variations with time were used to determine the position of the North Pole of the cometary nucleus. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comet Hale—Bopp Shells Expansion: A CCD Study

Using a CCD camera attached to the 0.335 m and 0.20 m reflectors of S.A.S. Observatory (Novara, Italy), we followed the linear jets and shells of comet Hale–Bopp between May 1996 and May 1997. In addition to confirming the model of Sekanina and Bohenhardt (1997), the study of the linear jets provided indications concerning the orientation of the comet's axis of rotation over time. The study of the shells revealed that the speed at which they move away from the nucleus was not constant. A periodic variation of the shell expansion velocity may not be excluded : if so, a possible precessional effect on the axis of rotation of the comet's nucleus could explain this behavior. This revised version was published online in July 2006 with corrections to the Cover Date.     

Organic synthesis in the coma of Comet Hale–Bopp?

Several organic molecules have now been detected in the coma of Hale–Bopp. These species may either emanate from the nucleus, or, as has been suggested by Bockelée–Morvan et al., could be synthesized in the coma. We have modelled the gas phase chemistry which occurred in the coma of Hale–Bopp, concentrating on the observed organic molecules HCOOH, HCOOCH₃, HC₃N and CH₃CN. We find that gas phase chemical reactions are unable to synthesize the observed abundances of these molecules, so all these species are most probably present in the nuclear ice. We briefly discuss the implications of this result for the connection between cometary and interstellar ices.     

Observations of Rotating Jets of Carbon Monoxide in Comet Hale–Bopp with the Iram Interferometer

CO was observed on March 11, 1997 in comet Hale–Bopp with theIRAM Plateau de Bure interferometer. The maps show evidence for asymmetrical patterns, due to the Existence of CO jets. Analysis of the spectra and their velocity shifts shows that there is a spiral CO jet rotating in a plane almost perpendicular to the sky plane.This is the first time that rotating jets are observed for parent molecules.We have developed a 3-D model simulating rotating spiral jets of CO gas.We present here the comparison between the observations and our model.     

Maps of hco+ Emission in c/1995 o1 (Hale–Bopp)

On-the-Fly maps of emission from the HCO⁺ J = 3-2 transition at 267.6 GHz were obtained of C/1995 O1 (Hale-Bopp) on 1997 Mar 15.6 UT using the NRAO 12-m telescope with high spatial resolution. Unlike the relatively symmetric and centralized maps of the neutral species CO, HCN and H₂CO, the spatial extent of HCO⁺ emission is very diffuse with a complex structure characterized by at least two physically different regions. The bulk of the HCO⁺ emission peaks in intensity ∼175,000 km anti-sunward from the nuclear position. This peak emission does not fall directly along the anti-sunward direction, but is rotated by ∼10 degrees toward the east from the anti-sunward direction. A substantial void, or decrease, of HCO⁺ emission is observed within ∼ 55,000 km of the nucleus. The HCO⁺ emission in this void is roughly half the intensity of the emission observed 100,000 km away. This decrease of HCO⁺ emission near the nucleus may indicate that production or excitation of HCO⁺ is inhibited, or perhaps that HCO⁺ is easily destroyed in the inner coma, especially within ∼50,000 km of the nucleus. This void roughly coincides with the approximate location and size of the so-called “diamagnetic cavity” in the coma and may mark a significant transition region in the inner coma of Hale-Bopp This revised version was published online in July 2006 with corrections to the Cover Date.     

1997年3月4日海尔-波普彗星的小规模分裂

１　引言彗核分裂是彗星的最重要特征之一．至１９８２年止文献记录共观测到２２个彗核分裂,３３个次核［１］．１９８６年哈雷彗星回归时观测到彗核的分裂［２］．１９９６年紫金山天文台２００ｍｍ赤道望远镜和青岛观象台同时观测到百武彗星的分裂［３］．海尔波普彗星从１９９５年８月到１０月曾爆发５次［４］．１９９６年３月至１２月不断有喷流射出,彗核活动日趋剧烈［５］．１９９７年３月４日我们观测到彗核的小规模分裂及喷流特征,３月３日我们观测到海尔波普彗星近核照片上有喷流,这可能是３月４日彗核小块分裂的前奏．３…     

On So In Comets

The solution of the statistical equilibrium equations for the SO molecule is used to estimate the expected intensities of microwave lines. The observed fluxes of the microwave lines of SO in Comet Hale–Bopp require approximately 1.8 10²⁸ mol/sec which give fluxes in the A³Π - X³Σ⁻bands below the observable limit, consistent with the observations. This revised version was published online in July 2006 with corrections to the Cover Date.