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The Minor Planet Bulletin (Warner Et Al THE MINOR PLANET BULLETIN OF THE MINOR PLANETS SECTION OF THE BULLETIN ASSOCIATION OF LUNAR AND PLANETARY OBSERVERS VOLUME 39, NUMBER 3, A.D. 2012 JULY-SEPTEMBER 99. ROTATION PERIOD DETERMINATION FOR 203 others, were also allowed. The only way to fill the large gap in POMPEJA – ANOTHER TRIUMPH OF GLOBAL phase coverage at a single observatory for an Earth commensurate COLLABORATION object is to obtain data from other observatories widely spaced in longitude. Andrea Ferrero in Italy and Hiromi and Hiroko Frederick Pilcher Hamanowa in Japan obtained at the first author's request the 4438 Organ Mesa Loop additional observations required to enable full phase coverage. A Las Cruces, NM 88011 USA total of 14 sessions 2011 Nov. 10 - 2012 Jan. 25 showed a 24.052 [email protected] ± 0.001 hour period, amplitude 0.10 ± 0.01 magnitude and unsymmetric bimodal lightcurve. A lightcurve phased to twice this Andrea Ferrero period showed two halves which were within observational error Bigmuskie Observatory (B88) the same as each other and as the 24.052 hour lightcurve. An via Italo Aresca 12, 14047 Mombercelli, Asti, ITALY irregularly shaped asteroid which was invariant over a 180 degree rotation would be required to produce the 48.1 hour lightcurve. Hiromi Hamanowa, Hiroko Hamanowa The probability of such a symmetric shape for an otherwise Hamanowa Astronomical Observatory irregular real asteroid is so small that it may be safely rejected. 4-34 Hikarigaoka Nukazawa Motomiya Fukushima JAPAN Hence we claim that the 24.052 hour period is the correct one. To make the lightcurve more legible the large number of data points (Received: 30 January) have been binned in sets of three points with a maximum of five Early observations by the first author yielded a rotation minutes between points. period value for 203 Pompeja that was very close to References being Earth commensurate. Additional observations by other observers widely spaced in longitude allowed full Di Martino, M (1984). “Lightcurves and Rotational Periods of Six phase coverage and showed a unique rotation period Asteroids.” Icarus 60 , 541-546. 24.052 ± 0.001 hours, amplitude 0.10 ± 0.01 magnitudes. Harris, A. W.; Pravec, P.; and Warner, B. D. (2011). “Asteroid Observations by F. Pilcher were obtained with a Meade 35 cm LX Lightcurve Data File: Dec. 11, 2011” 200 GPS S-C, SBIG STL 1001-E CCD, clear filter, unguided http://www.MinorPlanetObserver.com/astlc/default.htm. exposures. Those by A. Ferrero were with a 30 cm f/8 Ritchey- Chretien and SBIG ST9 CCD. H. and H. Hamanowa used a 40 cm Newtonian with SBIG ST-8 CCD. Image measurement, lightcurve analysis, and sharing of data were done with MPO Canopus software. According to Harris et al. (2011) the only previous period determination for 203 Pompeja is by Di Martino (1984) who found a descending branch of the lightcurve on each of 4 consecutive nights 1983 Sept. 10/11 through 13/14. He inferred a period of 46.6 hours, or possibly 23.3 hours if the lightcurve had only one maximum and minimum per cycle. There were no features such as maxima or minima which could be related on different nights, without which an accurate period determination could not be found. Observations by first author Pilcher on four nights 2011 Nov. 10 - 26 all showed identical appearing maxima consistent with a period near 24.05 hours, although periods slightly greater than 16 hours or 48 hours satisfied the data equally well. With more than two maxima per cycle periods near 32 hours or 36 hours, or perhaps Minor Planet Bulletin 39 (2012) Available on line http://www.minorplanet.info/mpbdownloads.html 100 PERIOD OF ASTEROID 696 LEONORA REVISED Figure 5 shows our data forced to an 18-hour period, whereas Figure 6 shows Warner’s data forced to the 27-hour period and the Marek Husárik, Ján Svoreň amplitude from our 2011 observations. Astronomical Institute of the Slovak Academy of Sciences SK-05960 Tatranská Lomnica, The Slovak Republic UT Date α LPAB BPAB Np Cov [email protected] (deg) (deg) (deg) (h) 2011 Sep 22.0 22.7 51.1 15.4 119 5.0 Radka Vašková 2011 Sep 26.0 22.0 51.9 15.5 310 8.7 Faculty of Science 2011 Oct 31.9 12.4 56.9 16.0 239 6.2 P.J. Šafárik University 2011 Nov 03.0 11.7 57.1 15.9 363 9.6 Park Angelinum 9 2011 Nov 03.9 11.4 57.2 15.9 292 9.5 SK-04001 Košice, The Slovak Republic 2011 Nov 18.0 8.1 58.0 15.6 224 5.6 2011 Nov 25.9 8.1 58.4 15.2 190 9.5 Table I. Observation circumstances in 2011 for 696 Leonora. (Received: 24 January) We describe observations and results of the photometric research of the asteroid 696 Leonora. Observations were obtained by a semi-automated 0.61-m f/4.3 photometric telescope at the Skalnaté Pleso Observatory. This instrument is equipped with a SBIG ST-10XME-Class 1 CCD camera. The asteroid was previously observed, but short observation runs for each night were poorly linked to each other, allowing different solutions for the rotation period. We were able to determine a rotation period of 26.8964 ± 0.0008 h based on the observations from 2011 September to November. The first photometric observations of asteroid 696 Leonora were made by Warner (2006). Six lightcurves obtained in 2005 September were used to estimate the rotational period of almost 18 Figure 1: Composite lightcurve of 696 Leonora based on Warner’s hours with an amplitude of 0.10 mag. However, his lightcurves data from 2005 and the estimated rotational period of 18 hours. almost always covered only one extrema (maximum or minimum). We produced a composite lightcurve (Fig. 1) based on the original lightcurves from Warner obtained from the ALCDEF database (http://minorplanetcenter.net/light_curve). In 2011 September we obtained two lightcurves, which offered a possibility of improving of Warner’s results (Fig. 2). Because the individual curves from 2005 cover relatively short time intervals, there is at least one additional, and more likely, solution for the rotation period of about 27-hour period (Fig. 3). We performed photometric observations in 7 nights from 2011 September to November with 0.61-m f/4.3 reflector at the Skalnaté Pleso Observatory. 60-second CCD frames were acquired with an SBIG ST-10XME using 3×3 binning (1.6 arcsec/px). We applied the standard calibration with dark and flat field frames with IRAF tools. The observation circumstances and aspect data for each night are listed in Table I, which gives the date for the mid-time of the observations, the solar phase angle, and the J2000.0 ecliptic coordinates of the phase angle bisector (PAB), which is the vector Figure 2: Two lightcurves from September 2011 which show a connecting the center of the asteroid and the midpoint of the great suspicion of irregularity of 18-hour period. circle arc between the sub-Earth and sub-solar points; for more information on the PAB, see Magnusson et al. (1989). The period and amplitude analysis were performed following the procedure described by Harris et al. (1989). All data in the composite lightcurve are relative and light-time corrected. Due to the better homogeneity of the data from October to November (e.g. phase angle values from October to November were in the range of 8.1–12.4 degrees versus 22.0 to 22.7 degrees in September), we used only that subset to find a rotation period of 26.8964 ± 0.0008 h (Fig. 4). Figure 3: Periodogram used for data from 2005 where another rotational period about 27 hours is possible. Minor Planet Bulletin 39 (2012) 101 References Harris, A.W., Young, J.W., Bowell, E., Martin, L.J., Millis, R.L., Poutanen, M., Scaltriti, F., Zappala, V., Schober, H.J., Debehogne, H., and Zeigler, K.W. (1989). “Photoelectric observations of asteroids 3, 24, 60, 261, and 863.” Icarus 77, 171–186 Magnusson, P., Barucci, M.A., Drummond, J.D., Lumme, K., Ostro, S.J., Surdej, J., Taylor, R.C., and Zappala, V. (1989). “Determination of pole orientations and shapes of asteroids” in Asteroids II (R.P. Binzel, T. Gehrels, M.S. Matthews, eds.) pp 66– 97. Univ. of Arizona, Tucson. Warner, B.D. (2006). “Asteroid lightcurve analysis at the Palmer Divide Observatory: July-September 2005.” Minor Planet Bull. 33, No. 2, 35–39. Warner, B.D., Harris, A.W., and Pravec, P. (2009). “The asteroid Figure 4: Composite lightcurve of 696 Leonora from 5 nights in 2011 lightcurve database” Icarus 202, 134–146. obtained at Skalnaté Pleso Observatory. ASTEROIDS LIGHTCURVE ANALYSIS AT THE ISON-NM OBSERVATORY: 3122 FLORENCE, (25916) 2001 CP44, (47035) 1998 WS, (137170) 1999 HF1 Leonid Elenin Keldysh Institute of Applied Mathematics RAS ISON-NM Observatory (MPC H15) 140007, Lyubertsy, Moscow region, 8th March str., 47-17 [email protected] Igor Molotov Keldysh Institute of Applied Mathematics RAS International Scientific Optical Network (ISON) Moscow, Miusskaya sq., 4 (Received: 16 February) Figure 5: Strong evidence of incorrectness of 18-hour period with our lightcurves from 2011. We present lightcurve analysis for four asteroids, including three NEAs, 3122 Florence, (25916) 2001 CP44, and (137170) 1999 HF1, and one Mars-crossing asteroid, (25916) 1998 WS. We were able to determine the rotation period for all four objects. For two of them, these are the first reported values. For 3122 Florence and 1999 HF1, we confirmed earlier results. All observations were carried out remotely at ISON-NM Observatory (NM, USA) in white light with 0.45-m f/2.8 astrograph and FLI ML09000-65 camera mounted at prime focus.
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