J/A+A/617/A57 Lowell Photometric Database asteroid models. II. (Durech+, 2018)
Asteroid models reconstructed from the Lowell Photometric Database and
WISE data.
Durech J., Hanus J, Ali-Lagoa V.
<Astron. Astrophys. 617, A57 (2018)>
=2018A&A...617A..57D 2018A&A...617A..57D (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets ; Models ; Photometry
Keywords: methods: data analysis - techniques: photometric -
minor planets, asteroids: general
Abstract:
Information about the spin state of asteroids is important for our
understanding of the dynamical processes affecting them. However, spin
properties of asteroids are known for only a small fraction of the
whole population.
To enlarge the sample of asteroids with a known rotation state and
basic shape properties, we combined sparse-in-time photometry from the
Lowell Observatory Database with flux measurements from NASA's WISE
satellite.
We applied the light curve inversion method to the combined data. The
thermal infrared data from WISE were treated as reflected light
because the shapes of thermal and visual light curves are similar
enough for our purposes. While sparse data cover a wide range of
geometries over many years, WISE data typically cover an interval of
tens of hours, which is comparable to the typical rotation period of
asteroids. The search for best-fitting models was done in the
framework of the Asteroids@home distributed computing project.
By processing the data for almost 75000 asteroids, we derived unique
shape models for about 900 of them. Some of them were already
available in the DAMIT database and served us as a consistency check
of our approach. In total, we derived new models for 662 asteroids,
which significantly increased the total number of asteroids for which
their rotation state and shape are known. For another 789 asteroids,
we were able to determine their sidereal rotation period and estimate
the ecliptic latitude of the spin axis direction. We studied the
distribution of spins in the asteroid population. Apart from updating
the statistics for the dependence of the distribution on asteroid
size, we revealed a significant discrepancy between the number of
prograde and retrograde rotators for asteroids smaller than about
10km.
Combining optical photometry with thermal infrared light curves is an
efficient approach to obtaining new physical models of asteroids. The
amount of asteroid photometry is continuously growing and joint
inversion of data from different surveys could lead to thousands of
new models in the near future.
Description:
Table 1: List of new asteroid models. For each asteroid, we list one
or two pole directions in the ecliptic coordinates (lambda_1, beta_1)
and (lambda_2, beta_2), the sidereal rotation period P, the rotation
period from LCDB PLCDB (if available) and its quality code U, the
number of sparse photometric data points N, the number of data points
in WISE bands W1, W2, W3, and W4, and the method that was used to
derive the rotation period: C - convex inversion, E - ellipsoids, CE -
both methods gave the same unique period. The accuracy of the sidereal
rotation period P is of the order of the last decimal place given. For
steroids marked with an asterisk, there is an inconsistency between P
and PLCDB.
Table 2: List of new partial models. For each asteroid, we list the
mean ecliptic latitude beta of the spin axis, its dispersion Delta,
and the meaning of other columns is the same as in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 662 List of new asteroid models
table2.dat 80 789 List of partial asteroid models
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See also:
J/A+A/587/A48 : Lowell Photometric Database asteroid models (Durech+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Number Asteroid number
9- 26 A18 --- Name Asteroid name or designation
28 A1 --- Ast [*] '*' if there is an inconsistency
between P and PLCDB
30- 32 I3 deg lambda1 Ecliptic pole longitude (J2000.0) for model 1
34- 36 I3 deg beta1 Ecliptic pole latitude (J2000.0) for model 1
38- 40 I3 deg lambda2 ? Ecliptic pole longitude (J2000.0) for model 2
42- 44 I3 deg beta2 ? Ecliptic pole latitude (J2000.0) for model 2
46- 54 A9 h P Sidereal period of rotation
56- 65 A10 h PLCDB ? Rotation period in the LCDB
67- 68 A2 --- U ? Uncertainty code according to LCDB
72- 74 I3 --- N Number of photometric points
76- 77 I2 --- W1 ? Number of points in W1 band
79- 80 I2 --- W2 ? Number of points in W2 band
82- 83 I2 --- W3 ? Number of points in W3 band
85- 86 I2 --- W4 ? Number of points in W4 band
88- 89 A2 --- Method Method used for period determination (G1)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Number Asteroid number
9- 26 A18 --- Name Asteroid name or designation
28 A1 --- Ast [*] '*' if there is an inconsistency
between P and PLCDB
30- 32 I3 deg beta Mean ecliptic pole latitude (J2000.0)
34- 35 I2 deg Delta Dispersion of beta
37- 45 A9 h P Sidereal period of rotation
47- 56 A10 h PLCDB ? Rotation period in the LCDB
58- 59 A2 --- U ? Uncertainty code according to LCDB
63- 65 I3 --- N Number of photometric points
67- 68 I2 --- W1 ? Number of points in W1 band
70- 71 I2 --- W2 ? Number of points in W2 band
73- 74 I2 --- W3 ? Number of points in W3 band
76- 77 I2 --- W4 ? Number of points in W4 band
79- 80 A2 --- Method Method used for period determination (G1)
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Global notes:
Note (G1): Method which was used to derive the unique rotation period
as follows:
C = convex inversion
E = ellipsoids
CE = both methods gave the same unique period.
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Acknowledgements:
Josef Durech, durech(at)sirrah.troja.mff.cuni.cz
(End) Josef Durech [Charles Univ. in Prague], Patricia Vannier [CDS] 12-Jul-2018