J/A+A/619/L3 (16) Psyche images (Viikinkoski+, 2018)
(16) Psyche: A mesosiderite-like asteroid?
Viikinkoski M., Vernazza P., Hanus J., Le Coroller H., Tazhenova K.,
Carry B., Marsset M., Drouard A., Marchis F., Fetick R., Fusco T.,
Durech J., Birlan M., Berthier J., Bartczak P., Dumas C., Castillo-Rogez J.,
Cipriani F., Colas F., Ferrais M., Grice J., Jehin E., Jorda L.,
Kaasalainen M., Kryszczynska A., Lamy P., Marciniak A., Michalowski T.,
Michel P., Pajuelo M., Podlewska-Gaca E., Santana-Ros T., Tanga P.,
Vachier F., Vigan A., Warner B., Witasse O., Yang B.
<Astron. Astrophys. 619, L3 (2018)>
=2018A&A...619L...3V 2018A&A...619L...3V (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Solar system ; Morphology
Keywords: minor planets, asteroids: general -
minor planets, asteroids: individual: (16) Psyche -
methods: observational - techniques: high angular resolution
Abstract:
Asteroid (16) Psyche is the target of the NASA Psyche mission. It is
considered one of the few main-belt bodies that could be an exposed
proto-planetary metallic core and that would thus be related to iron
meteorites. Such an association is however challenged by both its
near- and mid-infrared spectral properties and the reported estimates
of its density.
Here, we aim to refine the density of (16) Psyche to set further
constraints on its bulk composition and determine its potential
meteoritic analog.
We observed (16) Psyche with ESO VLT/SPHERE/ZIMPOL as part of our
large program (ID 199.C-0074). We used the high angular resolution of
these observations to refine Psyche's three-dimensional (3D) shape
model and subsequently its density when combined with the most recent
mass estimates. In addition, we searched for potential companions
around the asteroid.
We derived a bulk density of 3.99±0.26g/cm3 for Psyche. While such
density is incompatible at the 3-sigma level with any iron meteorites
(∼7.8g/cm3), it appears fully consistent with that of stony-iron
meteorites such as mesosiderites (density ∼4.25g/cm3). In addition,
we found no satellite in our images and set an upper limit on the
diameter of any non-detected satellite of 1460±200m at 150km from
Psyche (0.2%xRHill, the Hill radius) and 800±200m at 2000km
(3%xRHill).
Considering that the visible and near-infrared spectral properties of
mesosiderites are similar to those of Psyche, there is merit to a
long-published initial hypothesis that Psyche could be a plausible
candidate parent body for mesosiderites.
Description:
We observed Psyche with VLT/SPHERE/ZIMPOL at five different epochs,
close to its opposition. The data reduction was performed as described
in Vernazza et al. (2018, A&A, in press.).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 149 27 Mass estimates of (16) Psyche collected in the
literature
tablea2.dat 92 16 Diameter estimates of (16) Psyche collected
in the literature
list.dat 187 100 List of fits images
fits/* . 100 Individual fits images
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq ? Sequential number
3 A1 --- n_Seq [A] A for Average
5- 13 E9.4 kg Mass Mass
15- 23 E9.4 kg e_Mass rms uncertainty on Mass (3σ)
25- 30 F6.3 g/cm+3 rho ? Computed density
(using a diameter of 226.00±5.00)
32- 36 F5.3 g/cm+3 e_rho ? rms uncertainty on rho
38- 42 A5 --- Meth Method (1)
44 A1 --- Sel [XV] Selection flag (V for yes)
46-149 A104 --- Ref Reference
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Note (1): Methods as follows:
DEFL = Deflection
EPHEM = Ephemeris
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq ? Sequential number
3 A1 --- n_Seq [A] A for Average
5- 10 F6.2 km Diam Diameter
12- 16 F5.2 km e_Diam rms uncertainty on Diam (3σ)
18- 22 F5.3 g/cm+3 rho ? Computed density
24- 28 F5.3 g/cm+3 e_rho ? rms uncertainty on rho
30- 34 A5 --- Meth Method (1)
36 A1 --- Sel [XV] Selection flag (V for yes)
38- 92 A55 --- Ref Reference (1)
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Note (1): Methods as follows:
ADAM = Multidata 3D Modeling
IM-TE = Ellipsoid from Imaging
LCIMG = 3D Model scaled with Imaging
LCOCC = 3D Model scaled with Occultation
NEATM = Near-Earth Asteroid Thermal Model
RADAR = Radar Echoes
STM = Standard Thermal Model
TPM = Thermophysical Model
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 26 F7.5 arcsec/pix scale Scale of the image
28- 31 I4 --- Nx Number of pixels along X-axis
33- 36 I4 --- Ny Number of pixels along Y-axis
38- 60 A23 "datime" Obs.date Observation date (YYYY-MM-DDTHH:MM:SS.sss)
62- 65 I4 Kibyte size Size of FITS file
67-129 A63 --- FileName Name of FITS file, in subdirectory fits
131-187 A57 --- Title Title of the FITS file
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Acknowledgements:
Matti Viikinkoski, matti.viikinkoski(at)tut.fi
(End) Patricia Vannier [CDS] 09-Nov-2018