J/A+A/620/A91 New asteroid models (Durech+, 2018)
Reconstruction of asteroid spin states from Gaia DR2 photometry,
Durech J., Hanus J.
<Astron. Astrophys. 620, A91 (2018)>
=2018A&A...620A..91D 2018A&A...620A..91D (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets
Keywords: minor planets, asteroids: general - methods: data analysis -
techniques: photometric
Abstract:
In addition to stellar data, Gaia Data Release 2 (DR2) also contains
accurate astrometry and photometry of about 14000 asteroids covering
22 months of observations.
We used Gaia asteroid photometry to reconstruct rotation periods, spin
axis directions, and the coarse shapes of a subset of asteroids with
enough observations. One of our aims was to test the reliability of
the models with respect to the number of data points and to check the
consistency of these models with independent data. Another aim was to
produce new asteroid models to enlarge the sample of asteroids with
known spin and shape.
We used the lightcurve inversion method to scan the period and pole
parameter space to create final shape models that best reproduce the
observed data. To search for the sidereal rotation period, we also
used a simpler model of a geometrically scattering triaxial ellipsoid.
By processing about 5400 asteroids with at least ten observations in
DR2, we derived models for 173 asteroids, 129 of which are new. Models
of the remaining asteroids were already known from the inversion of
independent data, and we used them for verification and error
estimation. We also compared the formally best rotation periods based
on Gaia data with those derived from dense lightcurves.
We show that a correct rotation period can be determined even when the
number of observations N is less than 20, but the rate of false
solutions is high. For N>30, the solution of the inverse problem is
often successful and the parameters are likely to be correct in most
cases. These results are very promising because the final Gaia
catalogue should contain photometry for hundreds of thousands of
asteroids, typically with several tens of data points per object,
which should be sufficient for reliable spin reconstruction.
Description:
In Table A.1, we list 129 new models and their spin axis directions
(sometimes there are two possible solutions), the sidereal rotation
period, and the period reported in the LCDB. The LCDB period agrees
with our value in most cases. The asteroids for which the periods do
not agree and the LCDB period is reliable (higher uncertainty code U)
are marked with an asterisk.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 69 129 List of new asteroid models
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- n_Name [*e ] Note on Asteroid (1)
4- 8 I5 --- No Asteroid number
10- 25 A16 --- Name Asteroid name
27- 29 I3 deg lambda1 First pole direction, λ1
31- 33 I3 deg beta1 First pole direction, β1
35- 37 I3 deg lambda2 ? Second pole direction, λ2
39- 41 I3 deg beta2 ? Second pole direction, β2
43- 51 F9.5 h P Sideral rotation period (accuracy is of the
order of the last decimal place given)
53- 60 F8.4 h PLCDB ? Rotation period from LCDB (if available)
62- 63 A2 --- U Quality code
65- 66 I2 --- N Number of sparse photometric data points in DR2
68- 69 A2 --- Met Method used to derive the rotation period (2)
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Note (1): Note as follows:
* = there is an inconsistency between P and PLCDB
e = did not pass the χ2tr limit when 10% of points were removed.
Note (2): Methos as follows:
C = convex inversion
E = ellipsoids
CE = both methods gave the same unique period.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Nov-2018