J/ApJ/944/202 Mid-IR observations of (704) Interamnia (Jiang+, 2023)
Mid-IR observations of IRAS, AKARI, WISE/NEOWISE, and Subaru for large icy
asteroid (704) Interamnia: a new perspective of regolith properties and water
ice fraction.
Jiang H., Ji J., Yu L., Yang B., Hu S., Zhao Y.
<Astrophys. J., 944, 202 (2023)>
=2023ApJ...944..202J 2023ApJ...944..202J
ADC_Keywords: Minor planets; Solar system; Photometry, infrared
Keywords: Main belt asteroids ; Asteroids ; Small Solar System bodies
Abstract:
(704) Interamnia is one of the largest asteroids located in the outer
main-belt region, which may contain a large amount of water ice
underneath its surface. We observe this asteroid using 8.2m Subaru
telescope at mid-infrared wave bands and utilize a thermophysical
model for realistic surface layers to analyze mid-infrared data from
Subaru along with those of IRAS, AKARI, and Wide-field Infrared Survey
Explorer (WISE)/NEOWISE. We optimize the method to convert the WISE
magnitude to thermal infrared flux with temperature-dependent color
corrections, which can provide significant references for main-belt
asteroids at a large heliocentric distance with low surface
temperature. We derive best-fitting thermal parameters of Interamnia-a
mean regolith grain size of 190-180+460µm, with a roughness of
0.30-0.17+0.35 and rms slope of 27-9+13deg, thereby producing
thermal inertia ranging from 9 to 92Jm-2s-1/2K-1 due to seasonal
temperature variation. The geometric albedo and effective diameter are
evaluated to be 0.0472-0.0031+0.0033 and 339-11+12km,
respectively, being indicative of a bulk density of
1.86±0.63g/cm3. The low thermal inertia is consistent with typical
B/C-type asteroids with D≥100km. The tiny regolith grain size
suggests the presence of a fine regolith on the surface of Interamnia.
Moreover, the seasonal and diurnal temperature distribution indicates
that thermal features between the southern and northern hemispheres
appear to be very different. Finally, we present an estimation of
volume fraction of water ice of 9%-66% from the published grain
density and porosity of carbonaceous chondrites.
Description:
In this study, we conducted observations on Interamnia with the 8.2m
Subaru telescope at Maunakea on 2014 January 18 at 11:00 UTC, at a
solar phase angle of 8fdg399 and central wavelengths of 7.8, 8.7, 9.8,
10.3, 11.6, 12.5, 18.7, and 24.5um, using the Cooled MIR Camera and
Spectrometer (COMICS).
In addition, we further collected the mid-IR data of this asteroid
from IRAS, AKARI, and WISE, which are acquired from the NASA/IPAC
Infrared Science Archive (IRSA) with a search cone radius of 1". IRAS
observations contain four wave bands centered at 12, 25, 60, and
100um, with solar phase angle ranging from -17° to -15°. The
AKARI observations were obtained from the AKARI Asteroid Flux Catalog.
AKARI observed this asteroid at 9.0 and 18.0um in two separate epochs,
with a solar phase angle of 21°-22°. WISE surveyed the sky at
four wave bands, i.e., W1 (3.4um), W2 (4.6um), W3 (12um), and W4 (22um).
We query the WISE/NEOWISE mid-IR data from two catalogs, the WISE
All-Sky Single Exposure (L1b) Source Table and the NEOWISE-R Single
Exposure (L1b) Source Table.
Mid infrared data and observation geometries of IRAS, AKARI, Subaru
and WISE/NEOWISE are listed in Table A1. Note that WISE/NEOWSIE
observations are not color corrected here.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 81 361 Mid-infrared observations from IRAS, AKARI,
Subaru, WISE, and NEOWISE
--------------------------------------------------------------------------------
See also:
B/astorb : Orbits of Minor Planets (Bowell+, 2014-)
J/PASJ/63/1117 : Asteroid catalog using AKARI (AcuA). V1. (Usui+, 2011)
J/PASJ/71/1 : AKARI Near Infrared Asteroid Spectral Catalog V1 (Usui+, 2019)
J/A+A/633/A65 : (704) Interamnia images (Hanus+, 2020)
J/A+A/654/A56 : Largest main belt asteroids data (Vernazza+, 2021)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "Y/M/D" Obs.date Date of observation, UTC
12- 16 A5 "h:m" Obs.time Time of observation, UTC
18- 22 F5.1 um wave [3.4/100] Filter wavelength
24- 29 F6.2 --- Flux [9/858] Flux (1)
31- 35 F5.2 --- e_Flux [1/86] Uncertainty in flux (1)
37- 39 A3 --- x_Flux Units for flux (Jy or mJy)
41- 47 F7.3 deg alpha [-21.42/22.7] Solar phase angle
49- 53 F5.3 au rHelio [2.59/3.53] Heliocentric distance
55- 59 F5.3 au Dobs [2.12/3.77] Distance from the observer
61- 67 A7 --- Tel Telescope/Instrument/Mission used (2)
69- 81 F13.5 d JD Julian date converted from UTC date;
column added by CDS for convenience
--------------------------------------------------------------------------------
Note (1): WISE/NEOWISE fluxes are given without color correction.
Uncertainties in WISE 12um and 25um bands were fixed; see Section 2.1
Note (2): Telescope as follows:
NEOWISE = 194 occurrences
WISE = 116 occurrences
IRAS = 32 occurrences
AKARI = 11 occurrences
Subaru = 8 occurrences
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 31-Jan-2025