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 (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). 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) and recorded in the Minor Planet Center's (MPC) NEA database (http://minorplanetcenter.net/). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 136 39 Observations and Results
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
Bytes Format Units Label Explanations
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)?
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.
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 12-Jul-2018
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