with Astrovid StellaCam EX video CCD (0.83â²â²/pixel, FOV is 10â²x8â²). This small telescope was used to observe occultation of NZ Gem by the asteroid Thia,.
Solar and Stellar Physics Through Eclipses ASP Conference Series, Vol. 370, 2007 O. Demircan, S. O. Selam & B. Albayrak
First Results from Photometry and Astrometry of ¨ ITAK ˙ Selected Minor Planets at TUB National Observatory ¨ sık1 , I. Bikmaev4,5 , Z. Aslan1,2 , and K. Ulu¸c1 , I. Khamitov1 , T. Ozı¸ 1,3 Z. Tunca 1 TUB ¨ ITAK ˙ National Observatory of Turkey, Antalya, TURKEY 2 Akdeniz University, Antalya, TURKEY 3 Ege University, Izmir, ˙ TURKEY 4 Kazan State University, Russia 5 Academy of Sciences of Tatarstan, Kazan, RUSSIA Abstract. Large size of 1.5m Russian-Turkish Telescope (RTT150) (Aslan 2001) for the tasks of astrometry and photometry of minor planets (MPs) to¨ ITAK ˙ gether with astro-climatic conditions of the TUB National Observatory (TUG) in Turkey, allows us to get high-quality data. We observed the Apollo asteroid 2002 N Y40 with the RTT150 Telescope in BVRc-bands between 2002 July 30 and 2002 August 14. The difference detected in B −V color between the maximum and minimum of the phased light curve is attributed to a possible difference in albedo of different parts of the asteroid body. During the period of 2004-2005, we also observed 11 pre-calculated events of asteroid occultation and no positive events detected in all cases. The reasons of the negative results are discussed. Photometry of MPs according to USNO-B1 stars is presented.
1. 1.1.
Apollo Asteroid 2002 N Y40 Observations
We observed the Apollo asteroid 2002 N Y40 with the RTT150 telescope at TUG in BVRc-bands between 2002 July 30 and 2002 August 14, before its close approach to at 0.00035 AU to the Earth on 2002 August 18. Observations were made using 1kx1.5k ST-8E CCD camera (binning 2x2, 0.32′′ /pixel). We also made additional BVRc observations of the fields around the asteroid trajectory using 2kx2k Andor CCD camera (binning 2x2, 0.48′′ /pixel, FOV is 8′ x8 ′ at F/7.7) during a few photometric nights in 2003 August together with Landolt standard fields (Landolt 1992). The observational data is presented in Table 1. 1.2.
Photometry
All data were pre-processed (BIAS, DARK subtraction, flat-field correction) using IRAF.NOAO.CCDRED facilities. All stars up to 20th magnitude on Andor’s CCD frames were photometered and calibrated to standard photometric system using photometric solutions obtained with Landolt stars. Finally, BVRc photometry and astrometry of secondary standards were catalogued (astrometric solution of each frame was performed using USNO-B1 catalogue), and then the 358
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RTT150 observations for the Apollo asteroid 2002 N Y40 Date of Obs.
Band
UTstart
UTend
Nf rames
Exp. (sec)
20020730 20020802 20020803 20020803 20020804 20020804 20020805 20020805 20020805 20020814 20020814 20020814
V V V V R R B V R B V R
23.30 00.50 00.71 22.96 01.85 21.39 22.01 21.94 21.97 23.83 23.82 23.82
23.87 01.36 01.83 25.78 02.26 26.13 24.90 24.95 24.98 25.54 26.15 26.17
8 6 29 68 11 111 24 26 25 61 74 83
180 300 120 120 120 60 180 120 60 15 10 5
frames with the asteroid 2002 N Y40 were processed using the secondary standards of Landolt’s catalogue (Landolt 1992). For differential aperture photometry of the asteroid brightness, the secondary standard stars with photometric errors better than 0.01m were used. Photometric errors of asteroid brightness estimations are about 0.01m -0.02m . The photometry and astrometry were performed using the IDLPHOT and ASTROM packages from the IDL Astronomy User’s Library. 1.3.
Light curves
In Fig.1 we present the light curves of the asteroid in BVRc. The magnitudes obtained were converted to standard HG magnitudes using the definition of HG system by Bowell et al. (1989). m = H + 5 log(d ∗ r) − 2.5 log (l − G) ∗ P1 + G ∗ P2 , P2 = exp −1.87 ∗ tan(0.5f)1.22 P1 = exp −3.33 ∗ tan(0.5f)0.63
(1)
where, m is the observed magnitude of the asteroid, H its absolute magnitude, f the target’s apparent PHASE ANGLE as seen at observer’s location, d the geocentric distance in AU, and r the heliocentric distance in AU. The parameters m, f, d, r correspond to the time of observation. The parameters of the 2002 N Y40 (f,d,r ) were calculated using Horizons On-Line Ephemeris System (http://ssd.jpl.nasa.gov/cgi-bin/eph) for the observatory location (code number: A84) and time of observations. Slope parameter G is adopted as 0.15. Light curves were folded with rotational period P =19.98h (Pravec et al., 2004). The B-light curve is deeper by 0.1m at minimum phase than V and Rc light curves, the latter two have almost same depth at the same minimum. This means that B −V color is different at maximum from that at minimum of the light curve. The colors of the asteroid are given in Table 2. The composite (from BVRc) light curve is shown in Fig. 2. All light curves are adjusted to the V-light curve at maximum. The difference in B −V color may be interpreted as a possible difference in the albedo of different parts of the asteroid body.
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Figure 1.
The light curves of the asteroid N Y40 in BVRc.
Figure 2.
The composite light curve (from BVRc) of the asteroid N Y40 .
Table 2.
2.
The colors of the asteroid N Y40 Color
LCmax
LCmin
B −V V −Rc
1.02±0.03 0.24±0.02
1.16±0.03 0.22±0.02
The Asteroid Occultation of Stars
2.1.
Observations
In 2004 we started an observational program of occultation of stars by selected MPs using the RTT150 with the Andor CCD as the detector. The scientific aims of the program are exact ephemeris determination and studying geometrical properties of the MP involved, and estimating the angular radius of the occulted star. To calculate the time of occultation, the program WinOccult (http://www.lunar-occultations.com/iota/occult3.htm) written by D. Herald was used. The Tycho and UCAC catalogues were used as target catalogues. The stars from the catalogues and asteroids ephemerides are searched for the given place of observation using known physical parameters of asteroid and limits of observational constraints. The observational constraints used were as follows: 1. Minimum altitude of occultation star is 20 degrees.
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2. Maximum distance from the central line of the asteroid’s “shadow” as it travels across the Earth is 250 km, provided, of course, it is within the shadow. 3. Minimum magnitude drop is 0.5m 4. Minimum star magnitude is 14m
During the period of 2004-2005, we observed 11 pre-calculated events of asteroid occultation by scanning the fields with RTT150 telescope and Andor CCD without telescope tracking plus one event with a 20 cm, f/10 telescope with Astrovid StellaCam EX video CCD (0.83′′ /pixel, FOV is 10′ x8′ ). This small telescope was used to observe occultation of NZ Gem by the asteroid Thia, whose calculated central line was about 280 km east of the observatory. The calculated conditions of occultation and some physical parameters of asteroids are given in Table 3 and 4 respectively. Table 3.
Basic data for the occultation conditions.
Minor Planet
Occultation Star
Star Mag. (m )
Dur. (sec)
Mag. drop (m )
MP’s Alt. (deg)
Cent.Dist. (km)
1996 TC14 3232 Brest 1998 SE144 2086 Newell 792 Metcalfia 3983 Sakiko 412 Elisabetha 2052 Tamriko 2843 Yeti 7 Iris 405 Thia
TYC4919-01352 UCAC 28920963 TYC2426-00429 UCAC 19469004 2UCAC38226467 Hip 29188 2UCAC26135561 TYC5703-00636 TYC6304-00498 TYC6214-01471 FK6 2597
10.1 11.6 11.5 12.2 12.4 7.8 11.5 11.3 12.0 11.5 5.6
0.8 1.2 0.4 1.1 2.3 1.4 3.8 5.7 1.1 18.6 19.2
6.9 4.5 6.0 4.0 2.8 7.9 3.2 4.5 4.4 0.7 7.1
12 33 42 41 48 57 33 38 30 30 66
230 30 100 200 160 150 130 60 220 90 0
Table 4.
30.33 30.33 30.33 30.33 30.33 30.33 30.33 30.33 30.33 30.33 32.80
, , , , , , , , , , ,
36.83 36.83 36.83 36.83 36.83 36.83 36.83 36.83 36.83 36.83 36.05
Physical parameters and coordinates of the observed asteroids. Minor Planet 1996 TC14 3232 Brest 1998 SE144 2086 Newell 792 Metcalfia 3983 Sakiko 412 Elisabetha 2052 Tamriko 2843 Yeti 7 Iris 405 Thia
3.
Place (long , lat)
Absolute Mag. (m )
Diameter (km)
12.4 11.7 12.7 12.4 10.3 12.4 09.0 10.5 13.0 5.51 8.88
NaN NaN NaN NaN 60.73 16.39 90.96 30.45 12.00 199.83 95.07
RA (2000.0) 10 13 06 17 06 06 23 18 19 16 07
43 55 27 25 27 09 49 32 12 23 42
23.84 56.40 05.34 30.63 21.54 26.55 55.06 17.30 41.92 26.63 03.21
DEC (2000.0) -05 41 22.22 -08 13 28.68 +31 58 36.21 -29 32 23.08 +18 13 36.63 +27 11 37.97 -15 43 41.95 -13 57 52.63 -19 06 55.16 -21 53 27.81 +14 12 30.55
Results
We detected no positive events in all cases. As an example, light curve of MP00412 (Elisabetha) covering the interval of expected occultation is presented at Fig. 3c without any atmospheric correction. Time resolution is 0.017 sec/pixel. On 2 December 2005, the central path of “shadow” produced by MP00405 (Thia) was about 280 km east from the observatory. It was decided to make an expedition to the place of the central path. A sample of the video CCD observation can be downloaded from http://www.tug.tubitak.gov.tr/∼tuncay/ occultations/405 Thia video.wmv. After the negative result of the event, additional observations of Thia were carried out at TUG with the RTT150 on the night of
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Figure 3. Ephemerides difference (O-C) plot (a), photometry of the asteroid 405 Thia (b) and light curve of the negative occultation of the MP00412 (c).
Dec 26, 2005. Ephemerides difference (O-C) is plotted in Fig. 3a. We found no difference with error 0.05 arcsec. But this accuracy is not good enough to reach any conclusion about the occultation of 2 Dec 2005. We made the photometry of Thia using the catalog USNO-B1 (Fig. 3b). The reasons of the negative results may come from uncertainties in MP Ephemerides and the physical parameters of their shape and size. It is necessary to observe the MP and field of the star to be occulted before, and close enough to, the moment of the event to improve the ephemerides and star coordinates and in order to increase the probability of occultation. This may be done using small telescopes within Turkey as a joint program between professional and amateur astronomers. Acknowledgments. We thank to the night astronomer of TUG M. Parmaksızo˘glu for some occultation observations and Dr. A. Galeev from KSU for observations of N Y40 . References Aslan, Z., Bikmaev, I. F., Vitrichenko, E. A., Gumerov, R. I., Dembo, L. A., Kamus, S. F., Keskin, V., Kiziloglu, U., Pavlinsky, M. N., Panteleev, L. N., Sakhibullin, N. A., Selam, S. O., Sunyaev, R. A., Khamitov, I., & Yaskovich, A. L. 2001, Astronomy Letters, 27, 398 Bowell, E., Hapke, B., Domingue, D., Lumme, K., Peltoniemi, J., & Harris, A. W. 1989, in Asteroids II, ed. R. P. Binzel, T. Gehrels, & M. S. Matthews (Arizona University Press), 524 Landolt, A. U. 1992, AJ, 104, 340 Pravec, P., Harris, A. W., Scheirich, P., Kusnirak, P., Sarounova, L., Hergenrother, C. W., Mottola, S., Hicks, M. D., Masi, G., Krugly, Yu. N., Shevchenko, V. G., Nolan, M. C., Howell, E. S., Kaasalainen, M., Galad, A., Brown, P., DeGraff, D. R., Lambert, J. V., Cooney, W. R. Jr., & Foglia, S. 2004, Tumbling Asteroids, Icarus, 2004, March 23
