J/A+A/603/A55 WISE/NEOWISE Mars-crossing asteroids (Ali-Lagoa+, 2017)
Sizes and albedos of Mars-crossing asteroids from WISE/NEOWISE data
Ali-Lagoa V., Delbo M.
<Astron. Astrophys. 603, A55 (2017)>
=2017A&A...603A..55A 2017A&A...603A..55A (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Photometry, infrared ; Morphology
Keywords: minor planets, asteroids: general - surveys -
infrared: planetary systems
Abstract:
Mars-crossing asteroids (MCs) are a dynamically unstable group between
the main belt and the near-Earth populations. Characterising the
physical properties of a large sample of MCs can help to understand
the original sources of many near-Earth asteroids, some of which may
produce meteorites on Earth.
Our aim is to provide diameters and albedos of MCs with available
WISE/NEOWISE data.
We used the near-Earth asteroid thermal model to find the best-fitting
values of equivalent diameter and, whenever possible, the infrared
beaming parameter. With the diameter and tabulated asteroid absolute
magnitudes we also computed the visible geometric albedos.
We determined the diameters and beaming parameters of 404 objects
observed during the fully cryogenic phase of the WISE mission, most of
which have not been published elsewhere. We also obtained 1572
diameters from data from the 3-Band and posterior non-cryogenic phases
using a default value of beaming parameter. The average beaming
parameter is 1.2±0.2 for objects smaller than 10km, which
constitute most of our sample. This is higher than the typical value
of 1.0 found for the whole main belt and is possibly related to the
fact that WISE is able to observe many more small objects at shorter
heliocentric distances, i.e. at higher phase angles. We argue that
this is a better default value for modelling Mars-crossing asteroids
from the WISE/NEOWISE catalogue and discuss the effects of this choice
on the diameter and albedo distributions. We find a double-peaked
distribution for the visible geometric albedos, which is expected
since this population is compositionally diverse and includes objects
in the major spectral complexes. However, the distribution of beaming
parameters is homogeneous for both low- and high-albedo objects.
Description:
We fitted the near-Earth asteroid thermal model of Harris (1998,
Icarus, 131, 29) to WISE/NEOWISE thermal infrared data (see, e.g.,
Mainzer et al. 2011ApJ...736..100M 2011ApJ...736..100M, and Masiero et al. 2014, Cat.
J/ApJ/791/121). The table contains the best-fitting values of size and
beaming parameter. We note that the beaming parameter is a strictly
positive quantity, but a negative sign is given to indicate whenever
we could not fit it and had to assume a default value. We also provide
the visible geometric albedos computed from the diameter and the
tabulated absolute magnitudes.
Minimum relative errors of 10, 15, and 20 percent should be considered
for size, beaming parameter and albedo in those cases for which the
beaming parameter could be fitted. Otherwise, the minimum relative
errors in size and albedo increase to 20 and 40 percent (see, e.g.,
Mainzer et al. 2011ApJ...736..100M 2011ApJ...736..100M).
The asteroid absolute magnitudes and slope parameters retrieved from
the Minor Planet Center (MPC) are included, as well as the number of
observations used in each WISE band (nW2, nW3, nW4) and the
corresponding average values of heliocentric and geocentric distances
and phase angle of the observations. The ephemerides were retrieved
from the MIRIADE service
(http://vo.imcce.fr/webservices/miriade/?ephemph).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 99 2399 Best-fitting values of size and infrared beaming
parameter and corresponding geometric visible
albedos of Mars-crossing asteroids observed by
WISE/NEOWISE
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See also:
J/ApJ/791/121 : NIR albedos of main-belt asteroids (Masiero+, 2014)
J/A+A/591/A14 : PCF, SpecB or SDSSB asteroids parameters (Ali-Lagoa+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Object Asteroid designation (MPC-packed format)
12- 16 F5.2 mag H Asteroid absolute magnitude (MPC)
21- 24 F4.2 --- G Slope parameter (MPC)
29- 33 F5.2 km D Equivalent diameter
36- 40 F5.3 --- pV Visible geometric albedo
43- 47 F5.2 --- eta Infrared beaming parameter (negative sign
indicates that it was not fitted but fixed at
the corresponding positive value) (1)
50- 51 I2 --- nW2 Number of data fitted in band W2
54- 55 I2 --- nW3 Number of data fitted in band W3
58- 59 I2 --- nW4 Number of data fitted in band W4
62- 68 F7.5 AU r Average heliocentric distance
71- 77 F7.5 AU Delta Average geocentric distance
80- 87 F8.5 deg alpha Average phase angle
90- 99 F10.4 d MJD Modified Julian Date
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Note (1): The beaming parameter is a strictly positive quantity, so entries with
negative values indicate that the beaming parameter was fixed to the
corresponding positive value.
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Acknowledgements:
Victor Ali-Lagoa, vali(at)mpe.mpg.de
MPE, Garching bei Munchen, Germany
(End) Victor Ali-Lagoa [MPE, Germany], Patricia Vannier [CDS] 12-Jul-2017