THE MINOR PLANET BULLETIN OF THE MINOR PLANETS SECTION OF THE BULLETIN ASSOCIATION OF LUNAR AND PLANETARY OBSERVERS VOLUME 32, NUMBER 3, A.D. 2005 JULY-SEPTEMBER 45. 120 LACHESIS – A VERY SLOW ROTATOR were light-time corrected. Aspect data are listed in Table I, which also shows the (small) percentage of the lightcurve observed each Colin Bembrick night, due to the long period. Period analysis was carried out Mt Tarana Observatory using the “AVE” software (Barbera, 2004). Initial results indicated PO Box 1537, Bathurst, NSW, Australia a period close to 1.95 days and many trial phase stacks further [email protected] refined this to 1.910 days. The composite light curve is shown in Figure 1, where the assumption has been made that the two Bill Allen maxima are of approximately equal brightness. The arbitrary zero Vintage Lane Observatory phase maximum is at JD 2453077.240. 83 Vintage Lane, RD3, Blenheim, New Zealand Due to the long period, even nine nights of observations over two (Received: 17 January Revised: 12 May) weeks (less than 8 rotations) have not enabled us to cover the full phase curve. The period of 45.84 hours is the best fit to the current Minor planet 120 Lachesis appears to belong to the data. Further refinement of the period will require (probably) a group of slow rotators, with a synodic period of 45.84 ± combined effort by multiple observers – preferably at several 0.07 hours. The amplitude of the lightcurve at this longitudes. Asteroids of this size commonly have rotation rates of opposition was just over 0.2 magnitudes. -1.1 120 Lachesis Period = 1.910 days Minor planet 120 Lachesis was discovered on 10 April, 1872 from Mar-14 Mar-15 Marseilles by A. Borrelly. It was independently discovered the Mar-18 Mar-19 next day by C.H.F. Peters. It is named for one of the three Fates. Mar-21 Lachesis carries the scroll and determines the length of the thread Mar-24 Mar-25 -1.0 of life. This central main-belt asteroid is estimated to be174 km Mar-26 diameter and belongs to Tholen class C. The albedo is quoted as Mar-28 0.045 and the B-V= 0.70. The latest list of rotational parameters Mag (Harris & Warner, 2003) gives the rotation period as greater than 20 hours and the magnitude variability as > 0.14, with a reliability Delta of only 1. -0.9 Previous observations (Debehogne et al, 1983) over three nights in 1983 could not determine a period, but did suggest it was “much longer than 20 hours” and that this asteroid belonged to the slow rotator group. Observations over two nights in 1990 (Hainaut- -0.8 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Roulle et al., 1995) were also insufficient to determine a period, Phase but an overall magnitude variation of 0.14 was noted on one night. Observations were made on three nights in 1995 (Angeli et al., Table I. Aspect data for 120 Lachesis observations in 2004. 1999), but the low time resolution was totally inadequate to assist in determining the period of this minor planet. Observations by UT Date PAB PAB Phase %Phase one of the authors (CB) over four nights in 1999 and six nights in Long Lat Angle Coverage 2001 were also inadequate to resolve the period, although these 2004 Mar 14 177.1 -2.2 1.5 11 data did indicate that the period had to be longer than 20 hours and 2004 Mar 15 177.1 -2.2 1.2 14 the magnitude variation was >0.1. 2004 Mar 18 177.1 -2.3 1.0 8 2004 Mar 19 177.1 -2.4 1.3 6 Observations in 2004 were conducted from two sites – one in 2004 Mar 21 177.1 -2.4 1.9 3 NewZealand and one in Australia. The locations of these sites are 2004 Mar 24 177.0 -2.5 3.0 15 2004 Mar 25 177.0 -2.5 3.4 15 listed in Bembrick et al. (2004). In all, nine nights of observations 2004 Mar 26 177.0 -2.6 3.8 11 were acquired, using unfiltered differential photometry. All data 2004 Mar 28 177.0 -2.6 4.5 14 Minor Planet Bulletin 32 (2005) Available on line http://www.minorplanetobserver.com/mpb/default.htm 46 more than 2 rotations per day (Binzel et al., 1989), thus Lachesis is Bembrick, C.S., Richards, T., Bolt, G., Pereghy, B., Higgins, D. by comparison a very slow rotator. and Allen, W.H. (2004). “172 Baucis – A Slow Rotator”. Minor Planet Bulletin, 31, 51-52. Acknowledgements Binzel, R.P., Farinella, P., Zappala, V. and Cellino, A. (1989). Alan Gilmore of Mt John Observatory is thanked for his critical “Asteroid Rotation Rates.” In Asteroids II (Binzel, Richard P., comments on an early version of this light curve. Gehrels, Tom and Matthews, Mildred Shapley, eds.) pp416-441. Univ. Arizona Press, Tucson. References Debehogne, H., De Sanctis, G. and Zappala, V. (1983). Angeli, C. A., Lazzaro, D., Florczak, M.A., Betzler, A.S. and “Photelectric Photometry of Asteroids 45, 120, 776, 804, 814 and Carvano, J.M. (1999). “A contribution to the study of asteroids 1982 DV”. Icarus, 55, pp 236-244. with long rotational periods.” Planetary & Space Sci., 47, pp 699- 714. Hainaut-Roulle, M.-C., Hainaut, O.R. and Detal, A. (1995). “Lightcurves of selected minor planets.” Astron. Astrophys. Suppl. Barbera, R. (2004). “AVE” Analisis de Variabilidad Estelar, Ser., 112, pp 125-142. version 2.51. Grup d’Estudis Astronomics. http://usuarios.lycos.es/barbera/AVE/AveInternational.htm Harris, A.W. and Warner, B.D. (2003). “Minor PLanet Lightcurve Parameters”. Updated Dec. 15 2003. http://cfa-www.harvard.edu/iau/lists/LightcurveDat.html 2004-2005 WINTER OBSERVING CAMPAIGN AT Paramount mounts at the Oakley Observatory in Terre Haute, ROSE-HULMAN INSTITUTE: RESULTS FOR Indiana. The Tenagra telescope operates at f/7 with a CCD camera 1098 HAKONE, 1182 ILONA, 1294 ANTWERPIA, using a 1024x1024x24u SITe chip and the images were binned 2 1450 RAIMONDA, 2251 TIKHOV, AND by 2 (Schwartz, 2004). The Oakley Telescopes operate at f/7 with 2365 INTERKOSMOS two Apogee AP7 and one Apogee AP8 cameras. The AP7s have 512x511x24u SITe chips, one of which uses a V-filter, and the Crystal LeCrone AP8 has a 1024x1024x24u SITe chip. The exposures were 60 Don Addleman seconds for Tenagra and 240 seconds for Oakley images. Thomas Butler Erin Hudson Asteroids were selected for observation by using TheSky, Alex Mulvihill published by Software Bisque, to locate asteroids that were at an Chris Reichert elevation angle of between 20º and 30º one hour after local sunset. Ian Ross In addition, TheSky was set to show only asteroids between 14 and Harry Starnes 16 mag. Bright asteroids were avoided because we pay for a Richard Ditteon minimum 60 second exposure while using the Tenagra telescope. Rose-Hulman Institute of Technology CM 171 The asteroids were cross checked with the list of lightcurve 5500 Wabash Avenue parameters (Harris and Warner 2003). We tried to observe only Terre Haute, IN 47803 asteroids that did not have previously reported measurements or [email protected] had very uncertain published results. (Received: 25 March) Observation requests for the asteroids and Landolt reference stars were submitted by Ditteon using ASCII text files formatted for the TAO scheduling program (Schwartz, 2004). The resulting images CCD images recorded in November and December 2004 were downloaded via ftp along with flat field, dark and bias and January and February 2005 using the Tenagra 32- frames. Standard image processing was done using MaxImDL, inch telescope and three telescopes located at Rose- published by Diffraction Limited. Photometric measurements and Hulman’s Oakley Observatory yielded lightcurves and light curves were prepared using MPO Canopus, published by periods for six asteroids: 1098 Hakone, 7.14 ± 0.01 h, BDW Publishing. 0.40 mag; 1182 Ilona, 29.8 ± 0.1 h, 1.20 mag; 1294 Antwerpia, 6.63 ± 0.01 h, 0.40 mag; 1450 Raimonda, A total of 9 asteroids were observed during this campaign, but 12.66 ± 0.02 h, 0.64 mag; 2251 Tikhov, 5.67 ± 0.01 h, lightcurves were not found for all of these asteroids. If an asteroid 0.40 mag; and 2365 Interkosmos, 5.78 ± 0.01 h, 0.36 had a very small variation in brightness or if the signal-to-noise mag. In addition to these results, we found little or no ratio was too small, that asteroid was dropped from further lightcurve amplitude, possibly indicative of long observation. This allowed the maximum number of quality periods, for asteroids 1114 Lorraine, 1166 Sakuntala, observations with limited funds. The data on two asteroids (1166 and 4332 Milton. Sakuntala and 4332 Milton) turned out to be little more than noise, while the data on 1114 Lorraine had no observable magnitude variation. During the winter of 2004-2005 eight Rose-Hulman students (LeCrone, Addleman, Butler, Hudson, Mulvihill, Reichert, Ross, 1098 Hakone. Asteroid 1098 Hakone was discovered on 5 and Starnes) and a professor (Ditteon) obtained images with the September 1928 by O. Oikawa at Tokyo. It was named for a 32-inc Ritchey-Chretien telescope with a V-filter at the Tenagra composite volcanic mountain about 80 km from the observatory Observatory in Arizona and three 14-inch Celestron telescopes on Minor Planet Bulletin 32 (2005) 47 where the asteroid was discovered (Schmadel, 1999). A total of 55 Acknowledgements images were taken over three nights: 31 January, 3 February, and 4 February 2005.