J/ApJ/744/197 WISE/NEOWISE observations of Hilda asteroids (Grav+, 2012)
WISE/NEOWISE observations of the Hilda population: preliminary results.
Grav T., Mainzer A.K., Bauer J., Masiero J., Spahr T., McMillan R.S.,
Walker R., Cutri R., Wright E., Eisenhardt P.R., Blauvelt E., DeBaun E.,
Elsbury D., Gautier T., Gomillion S., Hand E., Wilkins A.
<Astrophys. J., 744, 197 (2012)>
=2012ApJ...744..197G 2012ApJ...744..197G
ADC_Keywords: Minor planets ; Infrared sources ; Surveys
Keywords: infrared: planetary systems - minor planets, asteroids: general -
surveys
Abstract:
We present the preliminary analysis of 1023 known asteroids in the
Hilda region of the solar system observed by the NEOWISE component of
the Wide-field Infrared Survey Explorer (WISE). The sizes of the
Hildas observed range from ∼3 to 200km. We find no size-albedo
dependency as reported by other projects. The albedos of our sample
are low, with a weighted mean value of pV=0.055±0.018, for all
sizes sampled by the NEOWISE survey. We observed a significant
fraction of the objects in the two known collisional families in the
Hilda population. It is found that the Hilda collisional family is
brighter, with a weighted mean albedo of pV=0.061±0.011, than the
general population and dominated by D-type asteroids, while the
Schubart collisional family is darker, with a weighted mean albedo of
pV=0.039±0.013. Using the reflected sunlight in the two shortest
WISE bandpasses, we are able to derive a method for taxonomic
classification of ∼10% of the Hildas detected in the NEOWISE survey.
For the Hildas with diameter larger than 30km, there are 67+7-15%
D-type asteroids and 26+17-5% C-/P-type asteroids (with the
majority of these being P-types).
Description:
The Wide-field Infrared Survey Explorer (WISE) is a National
Aeronautics and Space Administration (NASA) medium-class Explorer
mission designed to survey the entire sky in four infrared
wavelengths: 3.4, 4.6, 12, and 22um (denoted as W1, W2, W3, and W4
respectively; Wright et al. 2010AJ....140.1868W 2010AJ....140.1868W; Mainzer et al.
2005SPIE.5899..262M 2005SPIE.5899..262M). The survey collected over two million
observations of more than 157000 asteroids. The survey started on 2010
January 14 and exhausted its secondary tank cryogen on 2010 August 5.
Exhaustion of the primary tank cryogen occurred on 2010 October 1, but
the survey was continued until 2011 February 1, as the NEOWISE
Post-Cryogenic Mission, using only bands W1 and W2.
We define the Hildas in the most general sense, allowing their
semimajor axis to be in the range 3.7-4.2AU, with an eccentricity less
than 0.4 and an inclination less than 30°. To make sure that the
orbits are generally secure we also require the observed arc length to
be at least 18 days.
There are 1028 objects in the data set of objects observed by NEOWISE
during the fully cryogenic part of the survey that satisfy these
criteria (see Figure 2), and we label this sample as the long-arc
Hildas (LAH). Of these, 923 objects were associated with previously
known objects, while 105 objects were new discoveries that have
subsequently been linked to incidental astronomy in the Minor Planet
Center (MPC) one-night database or have received optical follow-up
after the object was reported to the MPC.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 1089 *Thermal model fits
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Note on table1.dat: This table contains the preliminary thermal fit results
based on the First Pass version of the WISE data processing as described in
the text. The NEOWISE project plans to produce an updated final catalog
of physical properties based on the Second Pass processing of the WISE
data using the updated version of the WISE Science Data System, with a
goal of delivering this updated catalog to NASA's Planetary Data System.
Two calibration papers (2011ApJ...731...53M 2011ApJ...731...53M & Mainzer et al, 2011,
Cat. J/ApJ/743/156) discuss the absolute calibration of the WISE data for
small Solar system bodies and should be consulted before comparing with data
derived from other sources. The quoted precision for each parameter follows
the object with the most significant figures for the error on that value in
the table. Readers are encouraged to check the WISE Explanatory Supplement
(Cutri et al. 2011, Cat. II/311) for details and updates.
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See also:
B/astorb : Orbits of Minor Planets (Bowell+ 2013)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
J/ApJ/743/156 : NEOWISE obs. of NEOs: preliminary results (Mainzer+, 2011)
J/ApJ/742/40 : Jovian Trojans asteroids with WISE/NEOWISE (Grav+, 2011)
J/ApJ/741/68 : Main Belt asteroids with WISE/NEOWISE. I. (Masiero+, 2011)
http://wise.ssl.berkeley.edu/ : WISE home page
http://www.minorplanetcenter.org/ : IAU Minor Planet Center home page
http://sirrah.troja.mff.cuni.cz/~mira/mp/trojans_hildas/ : Synthetix proper
elements of Hildas and Trojans
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- MPC Trojan asteroid name; MPC format
9- 13 F5.2 mag HMag Absolute H band magnitude
15- 18 F4.2 --- G Magnitude slope parameter
20- 25 F6.2 km Diam Diameter
27- 30 F4.2 km e_Diam Statistical error in Diam (1)
32- 36 F5.3 --- pV Optical geometrical albedo
38- 42 F5.3 --- e_pV Statistical error in pV (1)
44- 48 F5.3 --- eta Beaming parameter η (takes into account
the thermal inertia)
50- 54 F5.3 --- e_eta Statistical error in eta (1)
56- 60 F5.3 --- pIR IR geometrical albedo
62- 66 F5.3 --- e_pIR Statistical error in pIR (1)
68- 69 I2 --- N1 Number of WISE W1 (3.3um) observations
71- 72 I2 --- N2 Number of WISE W2 (4.6um) observations
74- 75 I2 --- N3 Number of WISE W3 (11.6um) observations
77- 78 I2 --- N4 Number of WISE W4 (22.1um) observations
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Note (1): Error values presented here represent the statistical errors on the
model fits, including Monte Carlo modeling of uncertainties for the
WISE magnitudes, H, G, and beaming and pIR when these two parameters
cannot be fit.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-Jun-2013