RevMexAA (Serie de Conferencias), 14, 103{150 (2002) ABSTRACTS OF CONTRIBUTED PAPERS OBSERVATIONS OF COMETARY NUCLEI, Knowledge of basic properties of the cometary en- FROM CASLEO vironment is desired to enhance the scientific return F. Artigue1, G. Tancredi1, J. Fern´andez1, of the mission. A coma model for 19P/Borrelly is R. Gil Hutton2, J. Licandro3, M. Melitta4 presented that consistently represents the cometary and H. Rickman5 environment from the nucleus surface to the solar wind interaction region (Benkhoff & Boice, P&SS CCD photometric observations of more than ten 44, 665, 1996; Wegmann et al., P&SS 46, 603, 1998). Jupiter Family comets were performed using the Neutral gas and plasma dynamics and spatial distri- 2.15-m telescope at CASLEO, Argentina in March butions of various cometary species are presented for 1995, March 1997 and May 1999. The data were re- scientific planning and risk assessment for the DS1 duced with IRAF in standard ways. We will do abso- encounter. Predictions of x-ray emissions are made lute photometry using DIGIPHOT/APPHOT pack- for coordinating in situ plasma measurements with age included in IRAF. Standars stars from Landolt Chandra observations as well as other predictions for (1992) and Stobie et al. (1985) will be used for cali- planning experiments during the encounter. bration purposes. Estimates for the effective radius Our major findings can be summarized as follows: of the nuclei will be computed considering a typical (1) Estimates of the dust environment show that the geometric albedo, pv = 0.04. Wherever possible, risk is very small for a mission-ending dust hazard cometary image profiles will be compared with stellar at the current flyby distance of about 1500 km. (2) profiles, in order to determine the existence of a faint Using estimates of the solar wind conditions and the coma. Many of the observed comets were active at gas production rate at the time of encounter, a bow heliocentric distances larger than 4 AU. This is part shock is expected at a distance of about 60,000 to of a long-term observational program designed to ob- 80,000 km along DS1s trajectory, however, DS1 will tain nuclear magnitudes estimates of a large sample not penetrate the contact surface. (3) At closest ap- of Jupiter family comets (Licandro et al., Icarus 147, proach, the plasma speed steadily decreases to about 161, 2000). 2 km s−1, with an ion temperature of about 2x105 K 4 1 and electron temperature of about 2x10 K (domi- Departamento de Astronom´ıa, Fac. de Ciencias, Igua 4225, nated by photoelectrons), and an ion number den- 11400 Montevideo, Uruguay −3 2 Observatorio Astron´omico F´elix Aguilar, Av. Benavidez sity of about 100 cm . (4) A kidney-bean shaped 8175 Oeste, 5407 Marquesado, San Juan, Argentina x-ray emission region of approximately 80,000 km by 3 Instituto de Astrof´ısica de Canarias, V´ıa L´actea s/n, La 60,000 km in extent is predicted as seen from earth Laguna, Tenerife, Spain 4 Facultad de Ciencias Astron´omicas y Geof´ısicas de La Plata, (40 degree aspect angle) with a maximum intensity −5 −2 −1 UNLP, Argentina of about 8x10 erg cm s , assuming their ori- 5 Astronomiska Observatoriet, Box 5151, S-751 20, Uppsala, gin is charge exchange of heavy, highly ionized solar Sweden wind ions with cometary neutrals, primarily water group species (Cravens, Geophys. Res. Lett. 24, 105, 1997). We wish to acknowledge funding from NASA for the DS1 Science Team, with additional support from NAO (Japan) and FAPESP (Brasil). PRE-ENCOUNTER MODELS OF COMET 19P/BORRELLY FOR THE DEEP SPACE 1 1 South West Research Institute, San Antonio, USA, and MISSION Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, 1 2 3 USP, Sao Pablo, Brazil [email protected] D.C. Boice , R. Wegmann , J.I. Watanabe 2 4 4 Max{Planck{Institut fur¨ Astrophysik, Garching, Germany A.A. de Almeida and M.V. Canaves 3 National Astronomical Observatory, Tokyo, Japan 4 Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, The Deep Space 1 Mission (DS1) is scheduled to en- USP, Sao Paulo, Brazil counter comet 19P/Borrelly on 22 September 2001. 103 104 ABSTRACTS COULD DYNAMIC PRESSURE EFFECTS of the Solar System. We present a new visible spec- CAUSE THE DISCONNECTION EVENTS IN troscopic survey of asteroids, the Small Solar Sys- COMET P/HALLEY? tem Objects Spectroscopic Survey (S3OS2). This M.R. Voelzke survey has been carried on between Nov. 1996 and Sep. 2001 at the 1,52-m telescope at ESO (La Silla, Universidade Cruzeiro do Sul, Brazil, Chile), aiming to contribute to a better understand- [email protected] ing of the compositional distribution in the main belt. More than 800 asteroids have been observed Cometary and solar wind data are compared with and the first results have been presented in Lazzaro the purpose of identifying the solar wind conditions et al. (BAAS 29, 975, 1997). Several families and which are associated with comet plasma tail discon- groups of asteroids have been studied, like the fami- nection events (DEs). The cometary data are from lies of Flora (Florczak et al., Icarus 133, 233, 1998), The International Halley Watch Atlas of Large-Scale Themis (Florczak et al., A&ASS 134, 463, 1998) and Phenomena (Brandt et al. 1992). A systematic vi- Eunomia (Lazzaro et al., Icarus 142, 445, 1999), and sual analysis of the atlas images (Voelzke & Mat- the groups of Hungaria and Phocaea (Carvano et al., suura, P&SS 46, 835, 1998) revealed, among other Icarus 149, 173, 2001). Among the results obtained morphological structures, 47 DEs along the plasma with our survey, the discovery of a basaltic asteroid tail of comet P/Halley. The solar wind data are in in the outer main belt (Lazzaro et al., Sci 288, 2030, situ measurements from IMP-8 (King, IMS Source 2000) should be stressed. The only basaltic aster- Book p10, 1982), which are used to construct the oids known in the belt were 4 Vesta and some small actual variation of solar wind speed, density and dy- asteroids considered as fragments of it. The discov- namic pressure during the analysed intervals. This ery of the basaltic crust of the asteroid 1459 Mag- work compares the onsets of these DEs with the solar nya indicates that a substantial thermal heating has wind dynamic pressure variations in order to clarify occurred in the outer belt. As a general result, al- if pressure effects play an important role in the for- though our data confirm earlier results about a con- mation of DEs and if they can even be considered tinuous trend of compositions in the asteroid belt, as the triggering mechanism. The analysis however they also reveal a more prominent mixing than pre- reveals a poor correlation (23%) between the onsets viously supposed. This mixing is more pronounced of P/Halley's DEs and the associated pressure ef- in small objects due to collisions and dynamical pro- fects. This result is in good agreement with Weg- cesses and also in \scattered" objects that have high- mann (A&A 294, 601, 1995) who concluded in an in- inclination and/or high eccentricity orbits. dependent and theoretical analysis, that about 25% of all tail disconnections must be caused by inter- 1 MCT/Observat´orio Nacional, 20921-400 Rio de Janeiro, planetary shocks. The DEs onsets of comet P/Halley Brazil analysed in this work, calculated from observational 2 CEFET, 80000 Curitiba, Brazil data, do not corroborate the idea that DEs are as- sociated with dynamic pressure effects. PHOTOMETRY OF ASTEROIDS MEMBERS OF MARIA AND THEMIS FAMILIES A.A. Alvarez1, S. Fern´andez2, J. Ahumada2 and R. Duffard3 S3OS2: A VISIBLE SPECTROSCOPIC SURVEY OF AROUND 800 ASTEROIDS In observations carried out during the last 3 years D. Lazzaro1, J.M. Carvano1, T. Moth´e-Diniz1, on asteroids members of Themis and Maria families, C.A. Angeli1, R. Duff´ard1 and M. Florczak2 we obtained light curves and rotational periods of members of that families. The observations were Most of the asteroids have their orbits between 2.2 made with the 154-cm telescope of Bosque Alegre and 3.3 A.U. from the Sun, in a region where the Astrophysical Station. The results shows that av- transition between terrestrial and giant planets takes erage rotational periods found in the Maria family place. Therefore, the identification of the composi- are smaller than the average periods in the fam- tional and mineralogical properties of a large sample ily of Themis. We found the rotational periods of these objects will ultimately led to a better un- of: (727) Niponia, (1996) Adams, (2151) Hadwiger, derstanding of the physical and chemical evolution (2429) Schurer, (2903) Zhubai and (4099) 1988AB5, ABSTRACTS 105 all from the family of Maria. From the family of GAUSS' FORMS OF THE LAGRANGE'S Themis we found the rotational periods of (996) Hi- EQUATIONS FOR THE ANALYTICAL laritas, (1171) Rusthawela and (1782) Schneller. SOLUTION OF THE POSTNEWTONIAN TWO BODY PROBLEM J.G. Portilla Name Family Period (hr) Amplitude (727) Niponia Maria 4.20 1.19 Observatorio Astron´omico Nacional, Universidad (1996) Adams Maria 3.30 0.4 Nacional de Colombia A.A. 2584, Bogot´a, Colombia (2151) Hadwiger Maria 2.72 0.33 [email protected] (2429) Schurer Maria 7.03 0.33 (2903) Zhubai Maria 6.15 0.48 The equations of motion of the n-body problem un- (4099) 1988AB5 Maria 3.25 0.25 der the General Relativity formalism are the so- (996) Hilaritas Themis 11.30 0.94 called EIH equations, now extensively used in the (1171) Rusthawela Themis 5.28 0.49 analytical and numerical theories necessary to con- (1782) Schneller Themis 7.70 0.63 struct the ephemeris of the bodies in the solar sys- 1 tem.