J/AJ/154/162 KMTNet-SAAO observation of near-Earth asteroids (Erasmus+, 2017)
Characterization of near-Earth asteroids using KMTNet-SAAO.
Erasmus N., Mommert M., Trilling D.E., Sickafoose A.A., van Gend C.,
Hora J.L.
<Astron. J., 154, 162 (2017)>
=2017AJ....154..162E 2017AJ....154..162E (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets ; Ephemerides ; Photometry, VRI ;
Surveys
Keywords: minor planets, asteroids: individual (near-Earth objects) - surveys -
techniques: photometric
Abstract:
We present here VRI spectrophotometry of 39 near-Earth asteroids
(NEAs) observed with the Sutherland, South Africa, node of the Korea
Microlensing Telescope Network (KMTNet). Of the 39 NEAs, 19 were
targeted, but because of KMTNet's large 2°x2° field of view,
20 serendipitous NEAs were also captured in the observing fields.
Targeted observations were performed within 44 days (median: 16 days,
min: 4 days) of each NEA's discovery date. Our broadband
spectrophotometry is reliable enough to distinguish among four
asteroid taxonomies and we were able to confidently categorize 31 of
the 39 observed targets as either an S-, C-, X-, or D-type asteroid by
means of a Machine Learning algorithm approach. Our data suggest that
the ratio between "stony" S-type NEAs and "not-stony" (C+X+D)-type NEAs,
with H magnitudes between 15 and 25, is roughly 1:1. Additionally, we
report ∼1 hr light curve data for each NEA, and of the 39 targets, we
were able to resolve the complete rotation period and amplitude for
six targets and report lower limits for the remaining targets.
Description:
Observations were made with the Sutherland, South Africa, node of the
KMTNet (Kim et al. 2016JKAS...49...37K 2016JKAS...49...37K). The telescope has a primary
mirror of 1.6 m in diameter and is fitted with four 9kx9k CCDs, mosaicking
the 2°x2° field of view. Each CCD covers 1°x1° of sky with
a plate-scale of 0.40 arcsec/pixel. The vertical and horizontal gaps
between the CCDs are 184" and 373", respectively. Johnson-Cousins B-, V-,
R-, and I-filters are installed and only sidereal tracking is available.
The minimum recommended exposure time for an efficient cyclical observation
is 60 s due to the large readout time of ∼75 s.
Observations were completed over 23 nights falling between 2016 October 25
and 2017 February 20, and newly discovered NEAs were specifically targeted
for this study. On average, 1-2 new NEAs are discovered every night
(Galache et al. 2015P&SS..111..155G 2015P&SS..111..155G) and recorded in the Minor Planet
Center's (MPC) NEA database (http://minorplanetcenter.net/).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 136 39 Observations and Results
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See also:
J/A+A/375/285 : Photometric observations of 9 Near-Earth Objects (Szabo+, 2001)
J/A+A/509/A94 : Lightcurves of 14 NEAs (Kwiatkowski+, 2010)
J/A+A/511/A40 : Near Earth Asteroids positions (Birlan+, 2010)
J/A+A/511/A49 : Lightcurves of 12 NEAs (Kwiatkowski+, 2010)
J/ApJ/743/156 : NEOWISE observations of NEOs: preliminary results
(Mainzer+, 2011)
J/AJ/152/163 : Mission Accessible Near-Earth Objects Survey (Thirouin+, 2016)
http://minorplanetcenter.net/ : IAU Minor Planet Center home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 I1 --- Sample [1/2] Targeted observation (1) or
serendipitously observed (2) target
3- 12 A10 --- ID Object identifier
14- 32 A19 --- Obs.Date Date of observation midpoint
(DD-MM-YYYYThh:mm:ss)
34- 43 A10 "date" Date Discovery date
45- 49 I5 d Obs-Disc [4/12542] Days between object discovery and
observation
51- 54 A4 "h:m" Texp Observation duration
56- 59 F4.1 mag HMag [14/24.2] Horizons absolute H band magnitude
(1)
61- 65 F5.2 mag Vmag [16.51/21.08] Johnson V band magnitude
67- 71 F5.2 mag V-R [-0.17/0.43] V-R solar corrected color
73- 76 F4.2 mag e_V-R [0.02/0.26] Uncertainty in V-R
78- 82 F5.2 mag V-I [-0.41/0.59] V-I solar corrected color
84- 87 F4.2 mag e_V-I [0.03/0.34] Uncertainty in V-I
89- 90 A2 --- l_Amp [≥ ] Limit flag on Amp (2)
92- 95 F4.2 mag Amp [0.04/1.13] Light curve amplitude, VRI spliced
data (2)
97-100 F4.2 mag e_Amp [0/0.19]? Uncertainty in Amp
102-103 A2 --- l_Per [≥ ] Limit flag on Per (2)
105-109 F5.1 min Per [20/144] Rotation period (2)
111-114 F4.1 min e_Per [0.9/25.9]? Uncertainty in Per
116-119 F4.2 --- Prob-S [0/0.99] S-type ("stony") near-Earth asteroid
probability
121-124 F4.2 --- Prob-X [0/0.85] X-type (several different possible
compositions) near-Earth asteroid probability
126-129 F4.2 --- Prob-C [0/1] C-type (carbonaceous) near-Earth asteroid
probability
131-134 F4.2 --- Prob-D [0/0.55] D-type (even more primitive material)
near-Earth asteroid probability
136 A1 --- PHA [N/Y] Potentially Hazardous Asteroid (PHA)?
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Note (1): Obtained from https://ssd.jpl.nasa.gov/horizons.cgi.
Note (2): Lower limit shown in cases where observational duration was
insufficient to observe entire light-curve period.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 12-Jul-2018