J/AJ/156/139 Main belt asteroid shape distrib. from Gaia DR2 (Mommert+, 2018)
The main belt asteroid shape distribution from Gaia Data Release 2.
Mommert M., McNeill A., Trilling D.E., Moskovitz N., Delbo' M.
<Astron. J., 156, 139 (2018)>
=2018AJ....156..139M 2018AJ....156..139M (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets
Keywords: catalogs - minor planets, asteroids: general - surveys
Abstract:
Gaia Data Release 2 (Cat. I/345) includes observational data for 14099
pre-selected asteroids. From the sparsely sampled G-band photometry,
we derive lower-limit light curve amplitudes for 11665 main belt asteroids
(MBA) in order to provide constraints on the distribution of shapes in
the asteroid main belt. Assuming a triaxial shape model for each asteroid,
defined through the axial aspect ratios a>b and b=c, we find an average
b/a=0.80±0.04 for the ensemble, which is in agreement with previous
results. By combining the Gaia data with asteroid properties from the
literature, we investigate possible correlations of the aspect ratio with
size, semimajor axis, geometric albedo, and intrinsic color. Based on
our model simulations, we find that MBAs greater than 50 km in diameter
on average have higher b/a aspect ratios (are rounder) than smaller
asteroids. We furthermore find significant differences in the shape
distribution of MBAs as a function of the other properties that do not
affect the average aspect ratios. We conclude that a more detailed
investigation of shape distribution correlations requires a larger data
sample than is provided in Gaia Data Release 2.
Description:
Gaia Data Release 2 (DR2; Spoto et al. 2018, Cat. I/345) includes
1977702 astrometric observations of 14099 pre-selected asteroids, observed
between 2014 August 5 and 2016 May 23. Solar system moving objects are
identified through association with known asteroids with well-defined
orbits. The majority of DR2 asteroids are MBAs, but the sample also
includes a small number of Near-Earth Asteroids, Jupiter Trojans, and
trans-Neptunian objects. Each "transit" of a target across the detector
array leads to nine individual detections across a typical time span on
the order of 40 s. Target positions and epochs are provided for individual
detections, whereas photometric information is averaged per transit.
Photometric information on asteroids in DR2 is limited to Gaia G-band
(0.33-1.0 µm) magnitudes, fluxes, and flux uncertainties.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 11665 DR2 (Cat. I/345) main belt asteroid lightcurve
amplitudes and auxiliary data
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJ/759/L8 : WISE/NEOWISE observations of main belt asteroids
(Masiero+, 2012)
J/ApJ/791/121 : NIR albedos of main-belt asteroids (Masiero+, 2014)
J/A+A/578/A42 : Main Belt asteroids observed by Spitzer (Ryan+, 2015)
J/A+A/596/A40 : Main-belt asteroids optical light curves (Szabo+, 2016)
J/A+A/620/A91 : New asteroid models (Durech+, 2018)
J/ApJS/237/19 : KMTNet LCs of ∼1000 main-belt asteroids (Erasmus+, 2018)
http://minorplanetcenter.net/ : Minor Planet Center database
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- MPC [8/159493] MPC target number
8- 11 F4.2 mag Amp [0.02/1.97] Lower limit lightcurve amplitude (1)
13- 14 I2 --- Nobs [4/52] Number of Gaia DR2 observations (2)
16- 19 F4.1 deg b_alpha [7.6/33.8] Lower limit solar phase angle, α
(3)
21- 24 F4.1 deg B_alpha [9.4/37.9] Upper limit solar phase angle, α
(3)
26- 30 F5.2 --- G12 [-0.52/1.52] Adopted photometric G12 slope
parameter as defined by Muinonen et al.
(2010Icar..209..542M 2010Icar..209..542M)
32- 35 F4.2 --- E_G12 [0/0.95] Upper G12 1σ uncertainty
37- 40 F4.2 --- e_G12 [0/0.95] Lower G12 1σ uncertainty
42 A1 --- r_G12 [ov] G12 slope parameter source (4)
44- 48 F5.2 --- a* [-0.3/0.3]? SDSS intrinsic color parameter (5)
50- 54 F5.3 AU a [1.578/4.302] Semi-major axis (6)
56- 60 F5.1 km Diam [1.6/298.8]? Target diameter (7)
62- 65 F4.2 --- pV [0.02/1]? Target geometric albedo, V band (7)
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Note (1): Lightcurve amplitude lower limit as derived with the method defined
in Section 3. We provide the nominal peak-to-peak value.
Note (2): Number of observations in DR2 (Cat. I/345) with photometric
measurements used in this analysis; all objects with Nobs<5 have been
removed from this sample.
Note (3): Solar phase angle range over which this object has been observed in
degrees. We provide the minimum (b_alpha) and maximum (B_alpha) solar phase
angle as queried from JPL Horizons (Giorgini et al. 1996DPS....28.2504G 1996DPS....28.2504G).
Note (4): Source as follows:
o = Oszkiewicz et al. (2011JQSRT.112.1919O 2011JQSRT.112.1919O);
v = Veres et al. (2015Icar..261...34V 2015Icar..261...34V).
Note (5): Color parameter a* as defined by Ivezic et al. (2001AJ....122.2749I 2001AJ....122.2749I)
and obtained from the Sloan Digitized Sky Survey Moving Object Catalog
(Ivezic et al. 2005PDSS...40.....I 2005PDSS...40.....I).
Note (6): Semi-major axis of the target as obtained from the Minor Planet Center
database (http://minorplanetcenter.net/).
Note (7): Diameter and geometric albedo as derived by Mainzer et al.
(2016PDSS..247.....M 2016PDSS..247.....M).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 07-Mar-2019