J/A+A/638/A84 PACS observations of large main-belt asteroids (Ali-Lagoa+, 2020)
Thermal properties of large main-belt asteroids observed by Herschel PACS.
Ali-Lagoa V., Mueller T.G., Kiss C., Szakats R., Marton G.,
Farkas-Takacs A., Bartczak P., Butkiewicz-Bak M., Dudzinski G.,
Marciniak A., Podlewska-Gaca E., Duffard R., Santos-Sanz P., Ortiz J.L.
<Astron. Astrophys. 638, A84 (2020)>
=2020A&A...638A..84A 2020A&A...638A..84A (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Infrared sources ; Photometry ; Optical
Keywords: minor planets, asteroids: general - infrared: planetary systems -
surveys
Abstract:
Non-resolved thermal infrared observations enable studies of thermal
and physical properties of asteroid surfaces provided the shape and
rotational properties of the target are well determined via
thermo-physical models. We used calibration-programme Herschel PACS
data (70, 100, 160 microns) and state-of-the-art shape models derived
from adaptive-optics observations and/or optical light curves to
constrain for the first time the thermal inertia of twelve large
main-belt asteroids. We also modelled previously well-characterised
targets such as (1) Ceres or (4) Vesta as they constitute important
benchmarks. Using the scale as a free parameter, most targets required
a re-scaling ∼5% consistent with what would be expected given the
absolute calibration error bars. This constitutes a good
cross-validation of the scaled shape models, although some targets
required larger re-scaling to reproduce the IR data. We obtained low
thermal inertias typical of large main belt asteroids studied before,
which continues to give support to the notion that these surfaces are
covered by fine-grained insulating regolith. Although the wavelengths
at which PACS observed are longwards of the emission peak for
main-belt asteroids, they proved to be extremely valuable to
constrain size and thermal inertia and not too sensitive to surface
roughness. Finally, we also propose a graphical approach to help
examine how different values of the exponent used for scaling the
thermal inertia as a function of heliocentric distance (i.e.
temperature) affect our interpretation of the results.
Description:
Herschel Space Observatory PACS observations used in this work. See
Mueller et al. (2005 ESA SP-577), Nielbock et al.
(2013ExA....36..631N 2013ExA....36..631N), Balog et al. (2014ExA....37..129B 2014ExA....37..129B), and Mueller
et al. (2014ExA....37..253M 2014ExA....37..253M) for details on the data set and observing
modes, and Kiss et al. (2014ExA....37..161K 2014ExA....37..161K) on the reduction
approach, which required non-standard strategies for a subset of the
observations. These fluxes will also be retrievable from the SBNAF
database (Szakats et al., 2020A&A...635A..54S 2020A&A...635A..54S) along with the other
data and all relevant references.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 59 12 *List of observed asteroids
tableb1.dat 126 420 Observed fluxes and related quantities
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Note on sources.dat: Parameters from B/astorb, Orbits of Minor Planets
(Bowell+ 2014).
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See also:
B/astorb : Orbits of Minor Planets (Bowell+ 2014)
Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Target Asteroid designation, e.g. (511) Davida
18- 21 F4.2 mag H Absolute magnitude H parameter
23- 27 F5.1 km Diam ? IRAS diameter (see E.F.Tedesco,
pp.1151-1161; catalog II/190)
29- 37 F9.6 deg i Inclination (1)
39- 48 F10.8 --- e Eccentricity (1)
50- 59 F10.8 AU a Semimajor axis (1)
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Note (1): the osculating elements are heliocentric, on J2000
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 16 A16 --- Target Asteroid designation, e.g. (511) Davida
18- 27 I10 --- ObsID Observation ID
29- 35 A7 --- ObsMod Observation mode
37- 49 F13.5 d ObsS Julian date at observation's start (JD)
51- 63 F13.5 d ObsE Julian date at observation's end (JD)
65- 69 A5 --- Channel Channel name (blue, red or green)
71- 78 F8.4 Jy Fband Calibrated in-band flux
80- 87 F8.4 Jy e_Fband Relative calibration in-band flux error
89- 92 F4.0 um lambda Reference wavelength (microns)
94-100 F7.3 Jy Fcc Colour-corrected flux density (1)
102-108 F7.3 Jy e_Fcc Colour-corrected flux error (2)
110-114 F5.3 au rh Heliocentric distance in astronomical units
116-120 F5.3 au Dobs Distance to Herschel in astronomical units
122-126 F5.1 deg alpha Phase angle of the observation (3)
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Note (1): Szakats et al. (2020A&A...635A..54S 2020A&A...635A..54S) explain the colour-correction
procedure in full detail.
Note (2): This error bar includes a 5% absolute calibration error.
Note (3): The sign corresponds to that of the vector product between the
heliocentric distance vector and the vector towards the observer (the Herschel
Space Observatory) in the asteroid reference frame.
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Acknowledgements:
Victor Ali Lagoa, vmalilagoa(at)gmail.com
References:
Mueller et al. (2005 ESA SP-577)
Herschel Calibration Steering Group, & ASTRO-F Calibration Team.
ISBN 92-9092-855-7
Nielbock et al. (2013ExA....36..631N 2013ExA....36..631N)
The Herschel PACS photometer calibration. A time dependent flux calibration
for the PACS chopped point-source photometry AOT mode
Balog et al. (2014ExA....37..129B 2014ExA....37..129B)
The Herschel-PACS photometer calibration. Point-source flux calibration for
scan maps
Kiss et al. (2014ExA....37..161K 2014ExA....37..161K)
Optimized Herschel/PACS photometer observing and data reduction strategies
for moving solar system targets
Mueller et al. (2014ExA....37..253M 2014ExA....37..253M)
Herschel celestial calibration sources. Four large main-belt asteroids as
prime flux calibrators for the far-IR/sub-mm range
Szakats et al. (2020A&A...635A..54S 2020A&A...635A..54S)
Small Bodies: Near and Far Database for thermal infrared observations of
small bodies in the Solar System.
(End) Victor Ali-Lagoa [MPE, Germany], Patricia Vannier [CDS] 07-May-2020