J/PASJ/71/1 AKARI Near Infrared Asteroid Spectral Catalog V1 (Usui+, 2019)
AKARI/IRC Near-Infrared Asteroid Spectroscopic Survey: AcuA-spec.
Usui F., Hasegawa S., Ootsubo T., Onaka, T.
<Publ. Astron. Soc. Jap. 71, 1 (2019)>
=2019PASJ...71....1U 2019PASJ...71....1U (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets ; Spectra, infrared
Mission_Name: AKARI
Keywords: infrared: planetary systems - minor planets, asteroids: general -
techniques: spectroscopic - space vehicles
Abstract:
Knowledge of water in the solar system is important for the
understanding of a wide range of evolutionary processes and the
thermal history of the solar system. To explore the existence of water
in the solar system, it is indispensable to investigate hydrated
minerals and/or water ice on asteroids. These water-related materials
show absorption features in the 3um band (wavelengths from 2.7 to
3.1um). We conducted a spectroscopic survey of asteroids in the 3um
band using the Infrared Camera (IRC) on board the Japanese infrared
satellite AKARI. In the warm mission period of AKARI, 147 pointed
observations were performed for 66 asteroids in the grism mode for
wavelengths from 2.5 to 5um. According to these observations, most
C-complex asteroids have clear absorption features (>10% with respect
to the continuum) related to hydrated minerals at a peak wavelength of
approximately 2.75um, while S-complex asteroids have no significant
features in this wavelength range. The present data are released to
the public as the Asteroid Catalog using AKARI Spectroscopic
Observations (AcuA-spec).
Description:
This catalog contains near-infrared (2.5-5.0 micron) low-resolution
(R∼100) spectra of main-belt asteroids obtained with the Infrared
Camera (IRC; Onaka et al., 2007PASJ...59S.401O 2007PASJ...59S.401O, Ohyama et al.,
2007PASJ...59S.411O 2007PASJ...59S.411O) onboard the infrared astronomical satellite AKARI
(Murakami et al., 2007PASJ...59S.369M 2007PASJ...59S.369M) in the warm mission period of
AKARI (called Phase 3). 147 pointed observations for 66 asteroids with
a diameter of 40km or larger were performed in the grism mode of 2.5-5
micron band. By subtracting thermal emission of asteroids themselves
and dividing with the solar spectrum, the reflectance spectra of
asteroids are retrieved. It should be noted that (a) the signal of 4
Vesta was saturated in the 3-micron band thoroughly and (b) the
thermal emission of 4015 Wilson-Harrington was dominated in the
3-micron band due to its high temperature. Thus the reflectance
spectra of these two objects could not be extracted. In total, the
reflectance spectra of 64 asteroids are summarized in this catalog
which comprises 22 C-complex, 17 S-complex, 22 X-complex, and 3
D-complex asteroids. There still remain the wavy patterns likely due
to the contamination of neighboring stars or insufficient data
reduction. These unreliable wavelengths are flagged in the spectral
data. Data users must be careful about these flagged spectra.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
target.dat 132 147 Target list
flux/* . 147 *Individual spectra of flux density
reflec/* . 64 *Individual spectra of relative reflectance
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Note on flux/*: The name of spectrum of flux density is represented by a
combination of asteroid number (Number), name (Name), and Observational ID
(ObsID) with extension as "NumberNameObsID.txt".
Note on reflec/*: The name of spectrum of relative reflectance is
represented by a combination of asteroid number (Number) and name (Name)
with extension as "Number_Name.txt".
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See also:
B/astorb : Orbits of Minor Planets (Bowell+ 2014)
Byte-by-byte Description of file: target.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Number Asteroid's number
6- 22 A17 --- Name Asteroid's name
24- 34 A11 --- ObsID Observational ID
36- 54 A19 "datime" Obs.date Observation date (UT)
56- 63 F8.4 deg RAdeg Right ascension (J2000)
65- 72 F8.4 deg DEdeg Declination (J2000)
74-111 A38 --- Flux Name of the file with spectrum of flux density
in subdirectory flux
113-132 A20 --- Rflec Name of the file with spectrum of relative
reflectance in subdirectory rflec
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Byte-by-byte Description of file: flux/*
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Bytes Format Units Label Explanations
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1- 5 F5.3 um lambda Wavelength in micron
7- 13 F7.2 mJy Flux Observed flux density
15- 20 F6.2 mJy e_Flux Uncertainty in Flux
22 I1 --- sflag [0/1] Saturation flag (G1)
24 I1 --- csflag [0/1] Stellar contamination flag (G2)
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Byte-by-byte Description of file: reflec/*
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Bytes Format Units Label Explanations
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1- 5 F5.3 um lambda Wavelength in micron
7- 12 F6.3 --- Refl Relative Reflectance, normalized at 2.6 micron
14- 18 F5.3 --- e_Refl Uncertainty in Relative Reflectance
20 I1 --- eflag [0/1] Error flag (1)
22 I1 --- sflag [0/1] Saturation flag (G1)
24 I1 --- ctflag [0/1] Thermal contamination flag (2)
26 I1 --- csflag [0/1] Stellar contamination flag (G2)
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Note (1): Error flag for uncertainty of the spectra>0.1 as follows:
0 = good
1 = large uncertainty in relative reflectance
Note (2): Thermal contamination flag (wavelength>lambda_trunc) as follows:
0 = not severely contaminated
1 = severely contaminated by thermal emission
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Global notes:
Note (G1): Saturation flag for bright objects as follows:
0 = not saturated
1 = saturated
Note (G2): Stellar contamination flag by neighboring stars as follows:
0 = not contaminated
1 = contaminated by neighboring star(s)
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History:
* 30-Nov-2018: Documentation prepared by Fumihiko Usui
* 13-Feb-2019: Reference updated (Usui et al. 2019)
Acknowledgements:
Fumihiko Usui, usui(at)cps-jp.org
(End) Fumihiko Usui [Kobe University], Patricia Vannier [CDS] 15-Feb-2019