ASTEROID LIGHTCURVE ANALYSIS AT THE PALMER DIVIDE OBSERVATORY: 2013 JANUARY – MARCH

Abstract

Lightcurves for 41 asteroids were obtained at the Palmer Divide Observatory (PDO) from 2013 January through March: 785 Zwetana, 1509 Esclangona, 1599 Giomus, 1925 Franklin-Adams, 2048 Dwornik, 2491 Tvashtri, 3007 Reaves, 3720 Hokkaido, 4719 Burnaby, 4736 Johnwood, 5841 Stone, (6394) 1990 QM2, (8825) 1988 MF, 9231 Shimaken, 9387 Tweedledee, (11405) 1999 CV3, 11437 Cardalda, 16669 Rionuevo, (18486) 1996 AS2, (27713) 1989 AA, 28126 Nydegger, (29242) 1992 HB4, (29298) 1993 SA14, (29308) 1993 UF1, (31354) 1998 TR3, (32750) 1981 EG9, (32772) 1986 JL, (35340) 1997 GV18, (41044) 1999 VW6, (56318) 1999 UR3, (66092) 1998 SD, (68537) 2001 VC123, (75648) 2000 AW59, (99008) 2001 DU52, (125738) 2001 XE116, (135486) 2001 XP2, (137199) 1999 KX4, (154347) 2002 XK4, (343098) 2009 DV42, (349068) 2006 YT13, and 2013 BE19. The 2013 results for 9387 Tweedledee lead to a revised analysis of the data from 2006 for that asteroid and resolved the ambiguous solution reported at that time.

CCD photometric observations of 41 asteroids were made at the Palmer Divide Observatory (PDO) from 2013 January to March. See the introduction in Warner (2010c) for a discussion of equipment, analysis software and methods, and overview of the lightcurve plot scaling. The “Reduced Magnitude” in the plots is Johnson V or Cousins R (indicated in the Y-axis title) corrected to unity distance by applying −5*log (rΔ) to the measured sky magnitudes with r and A being, respectively, the Sun-asteroid and Earth-asteroid distances in AU. The magnitudes were normalized to the phase angle given in parentheses, e.g., alpha(6.5°), using G = 0.15, unless otherwise stated. The horizontal axis is the rotational phase, ranging from 0.0 to 1.0.

For the sake of brevity in the following discussions on specific asteroids, only some of the previously reported results may be referenced. For a more complete listing, the reader is referred to the asteroid lightcurve database (LCDB, Warner et al., 2009). The on-line version allows direct queries that can be filtered a number of ways and the results saved to a text file. A set of text files, including the references with bibcodes, is also available for download at http://www.minorplanet.info/lightcurvedatabase.html. Readers are strongly encouraged to obtain, when possible, the original references listed in the LCDB for their work.

785 Zwetana

This 50 km Eunomia asteroid was observed to support radar observations being carried out about the same time. The period of 8.888 h had been previously determined by Behrend (2005) and Shepard et al. (2008). Analysis of the 2013 data from PDO found the same result within error bars.

1509 Esclangona

This is a known binary asteroid (Merline 2003). Warner (2005) and Polishook (2009) reported a period for the primary of about 3.252 h. The 2013 PDO results are consistent with those. Warner et al. (2010b) reported a secondary period of P = 6.6422 h with A = 0.04 mag but no evidence of mutual events (occultations and/or eclipses). It’s believed that the secondary period is due to the rotation of a satellite. Given the size and distance from the primary, the chances of observing mutual events are considered very unlikely. No evidence of the secondary period was seen in the 2013 data analysis.

1599 Giomus

This asteroid was observed to see if it would be possible to confirm one of two previously reported periods: 6.46 h (Clark 2010) and > 7.3 h (Garlitz 2013). Unfortunately, the low amplitude of 0.04 mag made finding a unique solution difficult, if not impossible. The period of 29.1 h reported here should not be given much weight.

1925 Franklin-Adams

This was a target of opportunity, i.e., an asteroid in the same field as a planned target. Behrend (2005) reported a period of 3.082 h. The PDO data analysis found a period of 2.978 h. The PDO data could not be fit to the slightly longer period.

2048 Dwornik

Schevchenko (2003), Warner (2011), and Skiff (2011) all reported a period of about 3.67 h for this Hungaria asteroid. The amplitude in 2013 was too low (0.04 mag) to find a definitive solution. The lightcurve presented here was forced to a period near the earlier results with a best fit of 3.717 h.

2491 Tvashtri

This Hungaria asteroid was observed by the author in 2008 (Warner 2008). A period of 4.0839 h was reported at that time. The results from the 2013 data analysis are in good agreement.

3007 Reaves

Pravec et al. (2013) found a period of 4.15554 h using data from 2007. Within error bars, the 2013 PDO results are the same.

3720 Hokkaido

This was a target of opportunity from the Flora group that managed to stay in the planned target field for an extended time. No previously reported period was found.

4719 Burnaby

Behrend (2005, 2008, 2009, 2012) reported a period of 8.2 h. Using the 2103 PDO data, there is a weak solution near this but the more dominant solution is at 13.01 h.

4736 Johnwood

This was the third time this Hungaria was observed at PDO (Warner 2005, 2010a). All three results were consistent with one another, as were those from Behrend (2005, 2008, 2009, 2012) who observed the asteroid in late 2012.

5841 Stone

The 2013 PDO data analysis found multiple solutions, all very weak and due to the low amplitude (0.04 mag). The solution presented here was the best fit to one near to previous results from PDO (Warner 2007a, 2010a) when the amplitude was larger and the solutions unambiguous.

(6394) 1990 QM2

The 2013 observations were follow-up to work at PDO on two previous occasions (Warner 2008, 2011). The period from 2008 was 3.768 h while in 2011 the period was found to be 3.6873 h. The 2013 results agree with the shorter period. The discrepancy is likely explained by the fact that the 2008 data set consisted of only two nights separated by 7 days. This produced a large number of alias solutions, one being near 3.68 h.

9387 Tweedledee

Warner (2007a) reported an ambiguous solution of 7.05 h with the alternate being 3.54 h, it not being certain if a bimodal (longer period) or monomodal (shorter period) solution was correct. Analysis of the data from 2013 found a period of 3.535 h with a curve that was sufficiently asymmetric so as to make the double-period of about 7 h very unlikely. In that light, the data from 2007 were re-analyzed and found to give a good fit to a period of 3.543 h with an amplitude of 0.10 mag (instead of 0.15 mag as originally reported). Lightcurves for both years based on the 3.5 h solutions are presented here.

(11405) 1999 CV3

Pravec et al. (2013) reported a period of 6.5113 h for this near-Earth asteroid (NEA) based on data obtained in 1999. The analysis of the 2013 PDO data found a period of 6.504 h, in good agreement with the earlier results.

(11437) Cardalda

This was the first time that a period for this Hungaria had been obtained at PDO or, apparently, anywhere else.

16669 Rionuevo

Analysis of the 2013 PDO data found a period of 4.953 h, in very good agreement with earlier results from PDO (Warner 2010a).

(18486) 1996 AS2

This was a target of opportunity. Galad (2008) reported an ambiguous period of 3.89 h with one of 3.59 h being possible. The results from PDO 2013 data analysis found 3.62 h based only one night but with coverage over more than one rotation. All indications are that the 3.89 h solution is incorrect and that one near 3.6 is more likely.

(29242) 1992 HB4

Earlier results for the period of this Hungaria (Warner 2010a, 2011) and those from 2013 are in good agreement with one another.

(29308) 1993 UF1

The period of 9.810 h (Warner 2010a) was confirmed by the analysis of the PDO data from 2013.

(31354) 1998 TR3

Warner (2007b) found a period of 35.39 h for this Hungaria. Within error bars, the results from 2013 were the same.

(32750) 1981 EG9

This target of opportunity is a main-belt asteroid with no previously reported period. The best that could be determined is that the period is long, likely on the order of four or more days.

(32772) 1986 JL

This is the first time this Hungaria was worked at PDO. The WISE survey (Mainzer et al. 2011) report an albedo of p_V = 0.1385. This would mean the asteroid is not a member of the Hungaria family, whose members have albedos on the order of p_V = 0.4.

(66092) 1998 SD

Long breaks due to weather prevented obtaining a more detailed lightcurve. A half-period solution of 223 h is shown, which gives a better indication of the period than the full-period plot at 448 h. It’s possible that the asteroid might be tumbling, but a much more extensive data set of well-calibrated data would be required to confirm that hypothesis.

(68537) 2001 VC123

There were no previous results found. The period and amplitude of the lightcurve make this a good candidate for being a binary. It should be given priority at future apparitions.

(75648) 2000 AW59

This member of the Eunomia group was a target of opportunity.

(99008) 2001 DU52

This target of opportunity is an inner main-belt asteroid with an estimated effective diameter of 2.5 km.

(125738) 2001 XE116

A member of the Flora group, this was also a target of opportunity.

(135486) 2001 XP2

The period of 69 h is a reasonable estimate because of the large amplitude and bimodal lightcurve. This is a Hungaria and, based on a high albedo from WISE (Mainzer et al. 2011), likely a family member.

(137199) 1999 KX4, (154347) 2002 XK4, (343098) 2009 DV42, (349068) 2006 YT13, and 2013 BE19

These are all near-Earth asteroids. The PDO observing program has been giving some preference to these objects as the need grows for finding the physical characteristics of the group, rotation rates being among the most readily determined traits. None of these had previously reported periods. 2013 BE19 is listed by the Minor Planet Center as a Potentially Hazardous Asteroid (PHA) although the JPL close approach tables do not show it among those with close approaches through 2200.

Table I.

Observing circumstances. Asteroids with (H) after the name are members of the Hungaria group/family. Asteroids with (N) after the name are near-Earth asteroids (q < 1.3 AU). The phase angle (α) is given at the start and end of each date range, unless it reached a minimum, which is then the second of three values. If a single value is given, the phase angle did not change significantly and the average value is given. L_PAB and B_PAB are each the average phase angle bisector longitude and latitude, unless two values are given (first/last date in range).

Number	Name	2013 (mm/dd)	Pts	Phase	LPAB	BPAB	Period	P.E.	Amp	A.E.
785	Zwetana	03/02–03/07	603	10.9,11.9	156	18	8.885	0.001	0.18	0.01
1509	Esclangona (H)	01/17–01/18	191	6.7,6.8	119	−9	3.252	0.005	0.11	0.01
1599	Giomus	02/02–02/08	401	3.7,5.4	127	7	29.1	0.5	0.04	0.01
1925	Franklin-Adams	01/04–01/05	172	6.2,6.7	91	−3	2.978	0.002	0.25	0.02
2048	Dwornik (H)	01/22–02/02	176	17.0,19.5	107	−24	3.717	0.001	0.04	0.01
2491	Tvashtri (H)	03/02–03/07	141	25.8,24.4	169	18	4.084	0.001	0.08	0.01
3007	Reaves	12/29–01/03*	127	12.3,14.2	71	2	4.160	0.002	0.45	0.02
3720	Hokkaido	12/29–01/03*	183	9.3,11.3	79	8	4.79	0.01	0.20	0.02
4719	Burnaby	12/21–12/23*	236	6.4,7.0	83	10	13.01	0.03	0.07	0.01
4736	Johnwood (H)	01/06–01/08	223	11.2,10.6	109	14	6.217	0.005	0.91	0.02
5841	Stone (H)	02/16–03/07	279	7.9,1.6,5.0	159	3	2.8896	0.0006	0.04	0.01
6394	1990 QM2 (H)	01/23–02/02	132	20.9,23.0	99	−26	3.6888	0.0004	0.30	0.02
8825	1988 MF (H)	01/23–02/09	610	19.6,16.5	146	21	40.651	0.009	0.95	0.02
9231	Shimaken	02/13–02/19	233	4.2,1.4	152	2	10.917	0.005	0.55	0.02
9387	Tweedledee (H)	02/12–02/19	232	5.7,1.1	152	1	3.535	0.002	0.09	0.01
9387	Tweedledee (H)	09/16–09/19^	157	13.9,13.5	3	15	3.543	0.002	0.10	0.01
11405	1999 CV3 (N)	01/19–01/22	167	18.2,19.3	108	−19	6.504	0.002	0.72	0.02
11437	Cardalda (H)	12/29–01/01*	112	26.1,26.3	90	35	2.926	0.002	0.31	0.02
16669	Rionuevo (H)	02/03–02/05	240	20.4	139	33	4.953	0.001	0.53	0.02
18486	1996 AS2	03/02	56	1.4	159	2	3.62	0.05	0.34	0.02
27713	1989 AA (H)	12/29–01/01*	122	16.4,18.0	73	1	3.999	0.002	0.82	0.03
28126	Nydegger	02/09–02/13	206	2.2,3.0	141	−4	3.783	0.005	0.11	0.02
29242	1992 HB4 (H)	01/17–01/18	111	21.6,21.8	96	−29	3.947	0.005	0.56	0.02
29298	1993 SA14 (H)	01/05–01/12	183	25.6,27.0	81	29	7.795	0.003	0.20	0.02
29308	1993 UF1 (H)	01/02–01/04	353	17.1,17.2	103	28	9.805	0.004	0.83	0.02
31354	1998 TR3 (H)	01/23–02/09	469	19.0,16.4	143	29	35.36	0.03	0.18	0.02
32750	1981 EG9	02/12–02/13	121	2.3,2.6	140	−5	100	30	>0.6
32772	1986 JL (H)	12/22–12/29*	209	13.7,14.6	95	19	6.047	0.005	0.69	0.02
35340	1997 VO18	01/05–01/12	192	7.9,10.5	87	−5	12.519	0.005	0.84	0.02
41044	1999 VW6	02/13–02/17	164	2.2,3.5	141	−4	2.734	0.001	0.21	0.02
56318	1999 UR3 (H)	01/04–01/05	142	10.7,11.4	91	5	3.541	0.002	0.36	0.02
66092	1998 SD (H)	02/09–03/07	569	2.4,16.7	141	−6	448	5	0.42	0.05
68537	2001 VC123 (H)	02/08–02/13	171	9.7,12.5	131	−10	2.997	0.001	0.16	0.02
75648	2000 AW59	02/12–02/13	100	2.4,2.7	141	−4	4.09	0.05	0.13	0.03
99008	2001 DU52	02/02–02/13	367	5.4,10.5	125	6	37.45	0.10	0.47	0.05
125738	2001 XE116	03/02	52	2.0	159	2	4.09	0.08	0.19	0.02
135486	2001 XP2 (H)	01/17–02/01	143	14.0,20.0	101	12	69	5	1.2	0.1
137199	1999 KX4 (N)	01/05–01/08	257	35.5,35.7	132	8	2.767	0.001	0.12	0.01
154347	2002 XK4 (N)	01/02–01/04	299	36.7,33.9	119	27	3.319	0.003	0.08	0.01
343098	2009 DV42 (N)	01/09–01/19	301	14.7,8.3	111	−5	9.658	0.006	0.06	0.01
349068	2006 YT13 (N)	01/19–01/21	308	8.6,13.9	118	8	2.433	0.001	0.11	0.01
	2013 BE19 (N)	01/21–01/23	304	41.0,36.5	138	17	115	10	0.40	0.05

^*2012 December for first (and second) date

^{^}2006