Abstract
Lightcurves for 36 near-Earth asteroids (NEAs) were obtained at the Center for Solar System Studies-Palmer Divide Station (CS3-PDS) from 2015 October-December.
CCD photometric observations of 36 near-Earth asteroids (NEAs) were made at the Center for Solar System Studies-Palmer Divide Station (CS3-PDS) from 2015 October-December. Table I lists the telescope/CCD camera combinations used for the observations. All the cameras use CCD chips from the KAF blue-enhanced family and so have essentially the same response. The pixel scales for the combinations range from 1.24-1.60 arcsec/pixel.
Table I.
List of CS3-PDS telescope/CCD camera combinations.
| Desig | Telescope | Camera |
|---|---|---|
| Squirt | 0.30–m f/6.3 Schmidt–Cass | ML–1001E |
| Borealis | 0.35–m f/9.1 Schmidt–Cass | STL–1001E |
| Eclipticalis | 0.35–m f/9.1 Schmidt–Cass | ML–1001E |
| Australius | 0.35–m f/9.1 Schmidt–Cass | STL–1001E |
| Zephyr | 0.50–m f/8.1 R–C | FLI–1001E |
All lightcurve observations were unfiltered since a clear filter can result in a 0.1-0.3 magnitude loss. The exposure duration varied depending on the asteroid’s brightness and sky motion. Guiding on a field star sometimes resulted in a trailed image for the asteroid.
Measurements were done using MPO Canopus. If necessary, an elliptical aperture with the long axis parallel to the asteroid’s path was used. The Comp Star Selector utility in MPO Canopus found up to five comparison stars of near solar-color for differential photometry. Catalog magnitudes were usually taken from the MPOSC3 catalog, which is based on the 2MASS catalog (http://www.ipac.caltech.edu/2mass) but with magnitudes converted from J-K to BVRI using formulae developed by Warner (2007). The nightly zero points have been found to be consistent to about ± 0.05 mag or better, but on occasion are as large as 0.1 mag. Period analysis is also done using MPO Canopus, which implements the FALC algorithm developed by Harris (Harris et al., 1989).
In the plots below, the “Reduced Magnitude” is Johnson V as indicated in the Y-axis title. These are values that have been converted from sky magnitudes to unity distance by applying −5*log (rΔ) to the measured sky magnitudes with r and Δ being, respectively, the Sun-asteroid and Earth-asteroid distances in AU. The magnitudes were normalized to the given phase angle, e.g., alpha(6.5°), using G = 0.15, unless otherwise stated. The X-axis is the rotational phase, ranging from −0.05 to 1.05.
For the sake of brevity, only some of the previously reported results may be referenced in the discussions on specific asteroids. For a more complete listing, the reader is directed to the asteroid lightcurve database (LCDB; Warner et al., 2009). The on-line version at http://www.minorplanet.info/lightcurvedatabase.html allows direct queries that can be filtered a number of ways and the results saved to a text file. A set of text files of the main LCDB tables, including the references with bibcodes, is also available for download. Readers are strongly encouraged to obtain, when possible, the original references listed in the LCDB for their work.
If the plot includes an amplitude, e.g., “Amp: 0.65”, this is the amplitude of the Fourier model curve and not necessarily the adopted amplitude for the lightcurve. The value is provided as a matter of convenience.
1620 Geographos.
The period and shape of this asteroid have been studied in detail (e.g., Hudson and Ostro, 1999; Higgins et al., 2008). The results from the CS3-PDS observations agree well with those earlier findings. The 2015 apparition featured about the minimum lightcurve amplitude previously seen. In some years, the amplitude has been nearly double: 2.03 mag.
(5646) 1990 TR.
This was the second time the author observed 1990 TR, the first being in 2012 (Warner, 2013) when the amplitude was only 0.12 mag. The 0.32 mag amplitude in 2015 would seem to indicate the asteroid presented a more equatorial view. The periods from the two apparitions are in good agreement.
(6611) 1993 VW.
Pravec et al. (2005web) reported the possibility that this NEA is a binary, finding a primary period of 2.5568 h and a secondary period of 17.19 h. No mutual events were seen that would have firmly confirmed the existence of a satellite. Analysis of the CS3-PDS data only added to the mystery. Two possible solutions evolved, one involving two periods, P1 = 3.40 ± 0.01 h and P2 = 9.34 ± 0.01 h, and the other a single period solution of PS = 6.831 ± 0.001 h. It’s worth noting that P1 is almost exactly 1/2PS. All attempts to fit the CS3 data to the periods found by Pravec et al. were unsatisfactory.
(11054) 1991 FA.
Pravec et al. (2001web) reported a solution of P = 2.57223 h, A = 0.08 mag, but no lightcurve is available. Their data set spanned almost two months starting in 2001 November. A period search using the CS3 data, which consisted of three consecutive nights, found a strong solution at 2.926 h and a ntoably weaker one at about 2.6 h. The CS3 were forced to fit a period in the range of 2.5-2.7 h, which found P = 2.615 h, A = 0.14 mag. However, that solution is not as good a fit.
(33342) 1998 WT24.
The period and shape of this NEA were well-determined by Busch et al. (2008) using radar observations. The 2015 apparition presented a good opportunity to study the evolution of the lightcurve over a three-week span.
The “All” plot shows what happens when trying to merge data sets with significantly different amplitudes and synodic periods, the latter especially if the total span of the observations covers a large number of rotations. The plots A-E show the evolution of the shape and amplitude of the lightcurve as the phase angle decreased. Overall, the synodic period increased by about 0.01 h from the first observations to the last while the asteroid phase angle decreased to towards 0°. This is usually an indication of retrograde rotation, i.e., a pole latitude λ < 0. The latitude found by Busch et al. (2008) was λ = −22°
(53426) 1999 SL5.
This appears to be the first reported period for this NEA. The solution is reliable for rotational studies but not fully secure. The next good opportunity for follow-up is 2023 August when it will again be at +59° and V ~ 17.6.
(88263) 2001 KQ1.
No previous entries were found in the LCDB for 2001 KO1. The large amplitude and lightcurve asymmetry virtually assure that the bimodal solution is correct (see Harris et al., 2014).
(112985) 2002 RS28.
Three different data sets from 2015 gave three different results. The first two (Warner, 2015; 2016) gave ambiguous results. Despite a 0.24 mag amplitude in 2015 July, the data led to three equally-likely solutions, one close the one found using the 2015 November data. The asteroid doesn’t get brighter than V = 17.0 again until 2025.
(137084) 1998 XS16.
Pravec et al. (1999web) found a period of 5.4211 h. The solution here is in good agreement.
(138852) 2000 WN10.
The periods found by Pravec et al. (2011web), Skiff et al. (2012), and from the CS3 data are in good agreement.
(152679) 1998 KU2.
No single period could be found, though one of about 125 h roughly fits a bimodal lightcurve. It’s very likely this asteroid is in a tumbling state (non-principal axis rotation, NAPR). See Pravec et al. (2014; 2005a).
(152978) 2000 GJ147.
This appears to be the first reported period for this NEA. Despite the noisy data, the amplitude and low phase angle made the bimodal solution almost certain. The next time the asteroid is brighter than V = 18.0 is 2020 November.
(155110) 2005 TB.
There were no previous entries in the LCDB for 2005 TB. The solution is considered secure. The next apparition brighter than V = 18.0 is 2025 November, at −62°.
(155334) 2006 DZ169.
This NEA was observed at CS3 in 2015 August (Warner, 2016) when the amplitude was 0.21 mag. The amplitude decreased to 0.17 mag for the October observations. This was expected since the phase angle dropped from 42° to 10° and lightcurve amplitude is known to decrease with phase angle (Zappala et al., 1990).
(159399) 1998 UL1.
This appears to be the first reported lightcurve for 1998 UL1. While no other solutions were of nearly equal fit to the Fourier model, this period should not be considered definitive.
(163899) 2003 SD220.
There are very slight hints that this asteroid is tumbling (the slopes of some sessions doesn’t quite match the model curve slope). Tumbling would not be unexpected since the approximate damping time to single axis rotation is greater than the age of the Solar System (see Pravec et al., 2014).
(194268) 2001 UY4.
There were no previous entries in the LCDB to help guide the period analysis. As the period spectrum shows, there are several likely solutions, the favored one being 5.91 h. Another solution, at 7.88 h, may be a fit by exclusion, where the Fourier modeling finds a lower RMS by minimizing the number of overlapping data points in the solution. Such a solution is often indicated when there is a significant gap in the lightcurve. It’s worth noting that the two periods have an integral ratio of 4:3.
On the other hand, when plotting the half periods of both solutions, the best fit came at 3.94 h, which would favor the 7.88 h solution, assuming a bimodal lightcurve. However, this may not be a good assumption given the low amplitude and phase angle (see Harris et al., 2014).
(194386) 2001 VG5.
The period for 2001 VG5 has been reported twice before: Polishook (2009; 6.6 h) and Koehn et al. (2014; 6.351 h). The results based on the CS3 data are in good agreement with Koehn et al.
(200754) 2001 WA25.
There were no previous entries in the LCDB for this asteroid. The result is considered almost secure. The large scatter in relation to the amplitude leaves the period a little in doubt, but mostly out of a sense of caution.
(241596) 1998 XM2.
The interesting shape of the lightcurve for 1998 XM2 may indicate a concavity at one end of an elongated body. Those interested in follow-up will have to wait until 2027 May for it to be V < 18.0 again.
(253106) 2002 UR3.
It’s very possible that 2002 UR3 is a tumbler. Attempts to find a more bimodal than trimodal solution were unsuccessful. The period is much longer than expected for a damping time equal to the age of the Solar System, making tumbling maybe more likely than not. The 2015 apparition at V = 15.6 was brighter than most. It “blazes” through the sky in 2028 when it reaches V = 14.3 at +62° declination.
(294739) 2008 CM.
This NEA became the subject of intense and detailed radar observations in late 2015. Optical observations were hampered by very fast sky motion and a nearly full moon at the time of closest approach. The asteroid was observed before (Warner, 2014) when a secure result of P = 3.054 h, A = 0.48 mag was found.
The lightcurves for 2015 Dec 27 and 28 differ in both amplitude and synodic period, with the latter having the shorter period and smaller amplitude. This follows since the phase angle was about 8-10° less on the second day (see Zappala et al., 1990). The combined lightcurve (“All”) gives an average period and amplitude but does not fit the data as well as the individual curves.
The most noticeable feature is the very sharp decline at about 0.45 and 0.95 rotation phase. It’s believed that this is the result in bad timing. During both observing runs, which used exposures of only 10 seconds with a 15-second pause between images and repositioned the telescope every 20 images, the script also forced a refocusing routine about every hour. This process took anywhere from 3-8 minutes. It appears that these breaks were almost synced to the rotation period and so occurred at the same places in the curve throughout each run. That is one explanation.
Another might be that scattered light from a nearly full moon being 30-40° away on the two runs created a gradient across the image and so, as the comp stars moved from right to left, the base differential magnitude would change and then reset when a new set of comparison stars was used. To check on this, two tests were run. The first was to remeasure the images and always use comparison stars on the right side of the image and, if possible, the middle half vertically. This would avoid at least half any gradient change. This did not make a difference. The shifts still occurred at the focusing breaks and the amplitude remained at about 0.4 mag.
The second test was to find the pixel values in a random sampling of images processed with master flat-fields and darks. For each image, the stars were removed leaving (almost) only sky background pixels. The image was then divided into 64 columns that were 16-pixels wide and 1024 pixels high. The average pixel value of the subregions of 16384 pixels was found and then plotted versus starting column, a sample of which is shown here.
The plot shows a nearly flat response from the left to right side of the image. The standard deviation of the mean of the column averages was 0.2%, or about 0.002 mag. A similar check was done dividing the images into 16-pixel high rows, to see if there was a gradient from top to bottom. The standard deviation was half that for the columns average.
Imaging when there the moon is in the sky can be problematic if the telescope is not well baffled throughout the optical path. However, waiting until the dark of the moon is not always an option. In fact, it often is not. Despite the tests run in this case, the unusual behavior of the lightcurves may have been due to moonlight or other systematic issues other than bad timing. It is worth noting that only one other time has such a problem been seen at CS3 with a fast-moving object where obvious systematic issues could be eliminated. There again, the shifts in the lightcurve were nearly in sync with the breaks for focusing runs.
This highlights the need when working objects with relatively short periods, i.e., P < 3 hours, to vary the imaging cadence as much as possible. This means not only random intervals between individual images but, as this case may show, also random intervals between repositioning or refocusing the telescope.
(442243) 2011 MD11.
There were no previous entries in the LCDB for 2011 MD11. The period makes it a potential binary asteroid candidate. The next good follow-up opportunity comes in 2019 October at V ~ 17.7, Dec +26°.
(443837) 2000 TJ1.
While there were no previous lightcurve results in the LCDB, it did include an entry from Thomas et al. (2014), who reported that the asteroid is of taxonomic type Sq based on warm-Spitzer IR observations. The next photometry opportunity comes in 2020 October when the asteroid will be V ~ 16.9 at +5° declination.
(450649) 2006 UY64.
There were no previous entries in the LCDB for 2006 UY64. A single period solution did not quite fit the data. A dual period analysis in MPO Canopus found two periods: P1 = 2.824 ± 0.002 h, A1 = 0.09 ± 0.01 mag and P2 = 4.800 ± 0.005 h, A2 = 0.05 ± 0.01 mag. The shorter period makes the asteroid a good binary candidate.
Assuming the second period is valid, it might represent a fully asynchronous satellite, i.e., one where the rotation period is not also the orbital period. The next chance for confirmation by radar or optical observations isn’t until 2024 October, when the asteroid will reach a minimum distance of 0.06 AU, V ~ 14.1, Dec +19°.
(452302) 1995 YR1.
This appears to be the first reported lightcurve period for this NEA. The period is considered nearly secure, the small issues being the low SNR and the fact that most observing runs covered less than half a cycle.
2007 EA26.
This appears to be the first reported period for 2007 EA26, an NEA with an estimated diameter of 200 meters.
2009 TK.
There were no previous entries in the LCDB for 2009 TK. The estimated size of only 100 meters made it possible that this was a superfast rotator, P < 2 h, and so exposures were kept to 30 seconds. Based on Pravec et al. (2000), this would avoid rotational smearing as long as the period was about 3 minutes or longer. The short exposures led to a higher than preferred SNR, but proved to be the right choice given the rotation period of just over 6 minutes.
The lightcurve shape is unusual but this may be due in part to the somewhat high phase angle. The double period, P ~ 0.216 h was tested. This produced a highly symmetrical lightcurve with both halves matching the one in the plot and was rejected.
2011 WN15.
There were no previous entries in the LCDB for 2011 WN15. The period of just less than 2.1 hours, the so-called “spin barrier” between rubble pile and strength-bound asteroids. This should not be considered overly significant. This asteroid could easily be a rubble pile with sufficient bonding forces to allow it to spin a little faster than might be expected possible. The spin barrier is not a hard-fast but “fuzzy line” at best and depends on any number of factors.
Here is another case where the large scatter in the data was overcome by having a large number of data points in observing runs that each covered a significant part of a cycle.
2011 YS62.
There were no previous entries in the LCDB for this NEA. The period is considered secure due to the amplitude and asymmetrical shape of the lightcurve.
2015 SZ.
There were no previous entries in the LCDB for 2015 SZ. While there were no outward signs of the asteroid being a tumbler, it would not be unexpected since the period for a damping time of 4.5 Gy is only 9 hours (see Pravec et al., 2014 and references therein). It’s possible that the low SNR data masked small-level tumbling.
Unfortunately, this will be the best result for this NEA for some time. It does not get brighter than V ~ 21 nor will it be within reach of existing radar facilities through 2050.
2015 XC.
This NEA proved to be a tumbler (Petr Pravec, private communications). The “Float” plot is the best fit solution using the full data set when searching for a single period in MPO Canopus.
This is very reminiscent of a plot in Harris et al. (2014) which was used to demonstrate how a “beat period” could be found for a tumbler with similar periods of rotation and precession. The amplitude of 0.64 mag precludes a complex shape (Harris et al., 2014), adding further evidence for the asteroid being in a tumbling state. Pravec found periods of P1 = 0.181099 h and P2 = 0.27998 h. However, these are not unique and other periods are possible, especially for P2. The P1 and P2 plots have been forced to these two periods for comparison purposes only.
2015 SV2.
Here is another long-period NEA that might be expected to show signs of tumbling but does not, at least that can be seen with the existing data set. There were no previous entries in the LCDB. The 2015 apparition was the last one through 2050 where the asteroid will be brighter than V ~ 20.
2015 WF13.
There were no previous entries in the LCDB for 2015 WF13, and likely won’t be any more (lightcurves at least) for some time. The NEA won’t get brighter than V ~ 23.6 through 2050. Fortunately, the amplitude of the lightcurve was sufficient to overcome the low SNR data and allow finding a secure period. The estimated diameter is only 60 meters, and so the superfast period of only 12.7 minutes was not unexpected. Because of its small size, exposures were limited to 30 seconds to avoid rotational smearing (see Pravec et al., 2000).
2015 TA25.
A limited data set and apparently somewhat long period conspired against finding a reliable solution for 2015 TA25. The period spectrum shows several equally possible solutions. The period of 15.53 h is adopted here based on fitting the data to half-periods and the best fit being near 7.8 hours. There were no previous entries in the LCDB.
2015 XU378.
This appears to be the first reported lightcurve for 2015 XU378. The period seems secure, which is fortunate since the asteroid won’t be brighter than V ~ 22 mag through 2050.
Table II.
Observing circumstances during the 2015 apparition. The Mid-date is approximate middle of each data set. The phase and phase angle bisector were computed for 0 UT for that date.
| Mid-date | Phase | PABL | PABB |
|---|---|---|---|
| Nov 23 | 69.8 | 97.6 | −15.6 |
| Nov 27 | 63.8 | 97.1 | −15.3 |
| Dec 03 | 49.8 | 93.3 | −14.8 |
| Dec 05 | 42.5 | 90.3 | −14.4 |
| Dec 11 | 23.5 | 70.6 | −9.7 |
Table III.
Observing circumstances.
| Number | Name | 2015 mm/dd | Pts | Phase | LPAB | BPAB | Period | P.E. | Amp | A.E. | Grp | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1620 | Geographos | 12/13–12/16 | 186 | 26.9,28.0 | 51 | 21 | 5.223 | 0.005 | 1.02 | 0.03 | NEA | |
| 5646 | 1990 | TR | 11/18–11/24 | 112 | 50.1,49.0 | 146 | 3 | 3.203 | 0.002 | 0.26 | 0.03 | NEA |
| 6611 | 1993 | VW | 10/11–11/15 | 340 | 8.5,6.9,21.4 | 27 | 5 | 2.63 | 0.01 | 0.05 | 0.02 | NEA |
| 11054 | 1991 | FA | 10/09–10/11 | 88 | 57.4,58.0 | 66 | 6 | 2.926 | 0.005 | 0.15 | 0.02 | NEA |
| 33342 | 1998 | WT24 | 11/22–12/12 | 1400 | 70.4,21.7,32.5 | 90 | −14 | 3.697 | 0.001 | 0.29 | 0.03 | NEA |
| 53426 | 1999 | SL5 | 10/12–10/19 | 122 | 36.1,32.3 | 9 | 32 | 5.03 | 0.05 | 0.15 | 0.03 | NEA |
| 88263 | 2001 | KQ1 | 10/11–10/29 | 202 | 38.1,35.6 | 68 | 4 | 13.16 | 0.01 | 0.52 | 0.03 | NEA |
| 112985 | 2002 | RS28 | 11/05–11/15 | 417 | 47.6,44.9 | 321 | 20 | 4.787 | 0.005 | 0.09 | 0.02 | NEA |
| 137084 | 1998 | XS16 | 10/11–10/14 | 123 | 71.7,68.6 | 18 | 61 | 5.419 | 0.005 | 1.18 | 0.03 | NEA |
| 138852 | 2000 | WN10 | 11/19–11/21 | 242 | 24.8,23.9 | 46 | −11 | 4.463 | 0.005 | 0.38 | 0.03 | NEA |
| 152679 | 1998 | KU2 | 10/24–11/11 | 1291 | 30.2,13.6 | 62 | −4 | T125 | 5 | 1.35 | 0.20 | NEA |
| 152978 | 2000 | GJ147 | 11/23–11/30 | 279 | 4.3,14.3 | 60 | 6 | 13.22 | 0.05 | 0.47 | 0.05 | NEA |
| 155110 | 2005 | TB | 10/27–10/30 | 205 | 21.7,19.7 | 31 | 17 | 3.479 | 0.005 | 0.43 | 0.03 | NEA |
| 155334 | 2006 | DZ169 | 10/19–10/23 | 137 | 9.0,11.6 | 15 | 1 | 4.68 | 0.02 | 0.17 | 0.03 | NEA |
| 159399 | 1998 | UL1 | 10/11–10/14 | 166 | 13.0,11.2 | 28 | 14 | 4.01 | 0.02 | 0.12 | 0.03 | NEA |
| 163899 | 2003 | SD220 | 11/06–11/28 | 740 | 82.0,80.7,81.9 | 100 | 21 | 285 | 5 | 2.2 | 0.1 | NEA |
| 194268 | 2001 | UY4 | 10/31–11/03 | 400 | 28.2,21.5 | 47 | −16 | 7.88 | 0.02 | 0.13 | 0.02 | NEA |
| 194386 | 2001 | VG5 | 12/01–12/03 | 155 | 1.5,3.3 | 67 | 0 | 6.38 | 0.01 | 0.4 | 0.03 | NEA |
| 200754 | 2001 | WA25 | 12/04–12/05 | 104 | 45.5,44.3 | 109 | 8 | 3.653 | 0.005 | 0.31 | 0.04 | NEA |
| 241596 | 1998 | XM2 | 10/07–10/10 | 167 | 53.1,52.1 | 13 | 49 | 8.75 | 0.02 | 0.4 | 0.03 | NEA |
| 253106 | 2002 | UR3 | 11/12–11/23 | 1650 | 4.9,4.1,22.6 | 76 | −1 | 180 | 5 | 0.36 | 0.03 | NEA |
|
| ||||||||||||
| 294739 | 2008 | CM | 12/27–12/27 | 982 | 52.9,52.9 | 120 | 16 | 3.041 | 0.004 | 0.44 | 0.02 | NEA |
| 294739 | 2008 | CM | 12/28–12/28 | 499 | 45.3,45.3 | 119 | 10 | 2.966 | 0.004 | 0.49 | 0.02 | NEA |
|
| ||||||||||||
| 442243 | 2011 | MD11 | 10/05–10/08 | 102 | 12.9,13.1 | 4 | −5 | 2.43 | 0.002 | 0.15 | 0.01 | NEA |
| 443837 | 2000 | TJ11 | 10/03–10/08 | 496 | 3.9,2.8,11.8 | 11 | −4 | 14.09 | 0.03 | 0.49 | 0.04 | NEA |
| 450649 | 2006 | UY64 | 10/31–11/03 | 536 | 44.2,49.7 | 14 | 13 | 2.824 | 0.002 | 0.09 | 0.02 | NEA |
| 452302 | 1995 | YR1 | 12/13–12/17 | 301 | 34.5,40.0 | 107 | −5 | 5.006 | 0.005 | 0.23 | 0.03 | NEA |
| 2007 | EA26 | 10/30–11/15 | 548 | 22.0,43.6 | 37 | 20 | 65.0 | 0.2 | 0.56 | 0.05 | NEA | |
| 2009 | TK | 10/07–10/07 | 433 | 27.7,27.7 | 26 | −8 | 0.10794 | 0.00005 | 0.28 | 0.04 | NEA | |
| 2011 | WN15 | 12/05–12/12 | 820 | 63.3,18.2 | 95 | 9 | 1.948 | 0.001 | 0.15 | 0.03 | NEA | |
| 2011 | YS62 | 12/01–12/04 | 462 | 40.0,43.4 | 53 | 19 | 17.53 | 0.05 | 0.42 | 0.03 | NEA | |
| 2015 | SZ | 10/04–10/09 | 816 | 17.7,30.5 | 27 | 0 | 41 | 1 | 1.33 | 0.10 | NEA | |
| 2015 | XC | 12/06–12/07 | 244 | 30.5,46.9 | 58 | 12 | T0.181099 | 0.000006 | 0.55 | 0.05 | NEA | |
| 2015 | SV2 | 12/02–12/18 | 1004 | 37.2,20.4 | 85 | 15 | 43.91 | 0.05 | 0.8 | 0.03 | NEA | |
| 2015 | WF13 | 12/04–12/05 | 361 | 51.3,47.7 | 46 | −2 | 0.21194 | 0.00005 | 0.23 | 0.05 | NEA | |
| 2015 | TA25 | 11/05–11/07 | 335 | 7.8,12.1 | 39 | 6 | A15.53 | 0.05 | 0.35 | 0.05 | NEA | |
| 2015 | XU378 | 12/17–12/18 | 562 | 59.5,59.7 | 59 | −1 | 3.021 | 0.005 | 0.3 | 0.04 | NEA | |
preferred period for an ambiguous solution.
period of primary in binary.
dominant period of a tumbler.
Pts is the number of data points used in the analysis. 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. LPAB and BPAB are, respectively the average phase angle bisector longitude and latitude, unless two values are given (first/last date in range). Grp is the orbital group of the asteroid. See Warner et al. (LCDB; 2009; Icarus 202, 134-146.).
Acknowledgements
Funding for PDS observations, analysis, and publication was provided by NASA grant NNX13AP56G. Work on the asteroid lightcurve database (LCDB) was also funded in part by National Science Foundation grants AST-1210099 and AST-1507535.
This research was made possible in part based on data from CMC15 Data Access Service at CAB (INTA-CSIC) and the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund. (http://svo2.cab.inta-csic.es/vocats/cmc15/).
This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. (http://www.ipac.caltech.edu/2mass/)
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