J/AJ/160/277 gri-light curve of near-Earth asteroid 2020 CD3 (Fedorets+, 2020)
Establishing Earth's minimoon population through characterization of asteroid
2020 CD3.
Fedorets G., Micheli M., Jedicke R., Naidu S.P., Farnocchia D., Granvik M.,
Moskovitz N., Schwamb M.E., Weryk R., Wierzchos K., Christensen E.,
Pruyne T., Bottke W.F., Ye Q., Wainscoat R., Devogele M., Buchanan L.E.,
Djupvik A.A., Faes D.M., Fohring D., Roediger J., Seccull T., Smith A.B.
<Astron. J., 160, 277 (2020)>
=2020AJ....160..277F 2020AJ....160..277F
ADC_Keywords: Solar system; Minor planets; Photometry, G band; Photometry, RI
Keywords: Near-Earth objects ; Asteroids ; Transient sources ; Astrometry ;
Broad band photometry ; Earth-moon system ; Light curves ;
Orbit determination
Abstract:
We report on our detailed characterization of Earth's second known
temporary natural satellite, or minimoon, asteroid 2020CD3. An
artificial origin can be ruled out based on its area-to-mass ratio and
broadband photometry, which suggest that it is a silicate asteroid
belonging to the S or V complex in asteroid taxonomy. The discovery of
2020CD3 allows for the first time a comparison between known minimoons
and theoretical models of their expected physical and dynamical
properties. The estimated diameter of 1.2-0.2+0.4m and geocentric
capture approximately a decade after the first known minimoon,
2006RH120, are in agreement with theoretical predictions. The capture
duration of 2020CD3 of at least 2.7yr is unexpectedly long compared to
the simulation average, but it is in agreement with simulated
minimoons that have close lunar encounters, providing additional
support for the orbital models. 2020CD3's atypical rotation period,
significantly longer than theoretical predictions, suggests that our
understanding of meter-scale asteroids needs revision. More
discoveries and a detailed characterization of the population can be
expected with the forthcoming Vera C. Rubin Observatory Legacy Survey
of Space and Time.
Description:
2020-CD3 was discovered on 2020 February 15.51 UT by the Catalina Sky
Survey (CSS) 1.5m telescope on Mt. Lemmon (MPC observatory code G96).
Multiple broadband photometric imaging was performed on 2020 February
24 with the 8.1m Frederick C. Gillett Gemini North Telescope located
on Maunakea, Hawai'i, USA. The Gemini Multi-Object Spectrograph (GMOS)
observations consisted of three r', g', i' sequences with the G0301,
G0303, and G0302 filters.
To obtain 2020-CD3's photometric lightcurve, we employed the Large
Monolithic Imager (LMI) on the 4.3m Lowell Discovery Telescope (LDT,
G37) for approximately 1hr on 2020 February 27 UTC. Exposures were
taken with 30 sintegrations using a broadband VR filter that provides
high throughput between approximately 500 and 700nm.
The 3.6m Canada-France-Hawaii Telescope (CFHT, 568) on Maunakea,
Hawaii, USA, was used to obtain astrometry using nonsidereal tracking
with exposures of up to 120s in gri-band MegaCam images with no pixel
binning.
Astrometric observations were also made with the Alhambra Faint Object
Spectrograph and Camera (ALFOSC) at the 2.5m Nordic Optical Telescope
(NOT, Z23) at the Roque de los Muchachos Observatory, La Palma, Canary
islands, Spain.
The University of Hawaii 2.2m (UH 2.2, 568) telescope was used for
astrometric observations with nonsidereal tracking at 2020-CD3's
apparent rates of motion in unfiltered 300s exposures. Additional
astrometric observations were extracted from dedicated early
observations obtained with the Calar Alto Schmidt telescope (Z84) in
Spain.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 85 71 Newly acquired or remeasured astrometric data for
2020 CD3
table4.dat 35 65 Lightcurve photometric data for 2020 CD3 obtained
with the LDT translated to the rP1 filter
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/A+A/507/495 : LCs of Datura and 2003 CL5 asteroids (Vokrouhlicky+ 2009)
J/A+A/508/1503 : Photometry of 3 main belt asteroids (Marciniak+, 2009)
J/A+A/509/A27 : Near-Earth asteroids & QSOs close approaches (Nedelcu+, 2010)
J/A+A/511/A49 : Lightcurves of 12 NEAs (Kwiatkowski+, 2010)
J/A+A/523/A48 : Gaia photometry (Jordi+, 2010)
J/A+A/527/A42 : Photometry of asteroid (21) Lutetia (de Leon+, 2011)
J/A+A/529/A107 : Photometry of 4 main belt asteroids (Marciniak+, 2011)
J/A+A/545/A131 : Photometry of 8 main belt asteroids (Marciniak+, 2012)
J/A+A/546/A72 : Light curves of Flora region asteroids (Kryszczynska+, 2012)
J/A+A/559/A106 : Time-series photometry of 2012 DA14 (Terai+, 2013)
J/A+A/562/A48 : Light curves of asteroid (25143) Itokawa (Lowry+, 2014)
J/A+A/596/A40 : Main-belt asteroids optical light curves (Szabo+, 2016)
J/A+A/598/A63 : 2015 TB145 light curve (Mueller+, 2017)
J/A+A/619/A123 : Lightcurves of Near-Earth Asteroid 3200 Phaethon (Kim+ 2018)
J/A+A/627/A172 : Near-Earth asteroid (1917) Cuyo opt. & IR obs. (Rozek+, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.Y [2020] UTC year of observation
6- 7 I2 "month" Obs.M UTC month of observation
9- 17 F9.6 d Obs.D UTC day of observation
19- 20 I2 h RAh [13/14] Hour of right ascension (J2000)
22- 23 I2 min RAm Minute of right ascension (J2000)
25- 30 F6.3 s RAs Second of right ascension (J2000)
32 A1 --- DE- [+] Sign of declination (J2000)
34- 35 I2 deg DEd [4/33] Degree of declination (J2000)
37- 38 I2 arcmin DEm Arcminute of declination (J2000)
40- 44 F5.2 arcsec DEs Arcsecond of of declination (J2000)
46- 50 F5.2 mag Gmag [19.6/25.6]? Gaia system magnitude (1)
52- 54 A3 --- Obser MPC observatory code
56- 60 F5.3 s e_RAs [0.03/0.32] Uncerrtainity in RAs
62- 66 F5.3 arcsec e_DEs [0.03/0.32] Uncertainity in DEs
68- 85 A18 --- Tel Telecope used
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Note (1): See Jordi+, 2010, J/A+A/523/A48
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 13 F13.7 d MJD [58906/58907] Modified Julian Date
15- 21 F7.4 mag magrp1 [22.6/23.2] Magnitude in rp1-filter
23- 28 F6.4 mag ezp [0.02/0.03] Incertitude due to the zero point
calibration (1)
30- 35 F6.4 mag einst [0.1/0.2] Incertitude due to instrument
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Note (1): The photometric calibration was performed by tying the VR
images to the Pan-STARRS1 rP1 band. This technique introduces errors
in the absolute photometric calibration as the bands are not identical
but they are significantly smaller than the typical uncertainty
(∼0.1-0.2mag) on the individual measurements.
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History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS], 18-Feb-2021