J/A+A/652/A141 Chariklo's system from stellar occultations (Morgado, 2021)
Refined physical parameters for Chariklo's body and rings from stellar
occultations observed between 2013 and 2020.
Morgado B.E., Sicardy B., Braga-Ribas F., Desmars J., Gomes-Junior A.R.,
Berard D., Leiva R., Ortiz J.L., Vieira-Martins R., Benedetti-Rossi G.,
Santos-Sanz P., Camargo J.I.B., Duffard R., Rommel F.L., Assafin M.,
Boufleur R.C., Colas F., Kretlow M., Beisker W., Sfair R., Snodgrass C.,
Morales N., Fernandez-Valenzuela E., Amaral L.S., Amarante A., Artola R.A.,
Backes M., Bath K-L., Bouley S., Buie M.W., Cacella P., Colazo C.A.,
Colque J.P., Dauvergne J-L., Dominik M., Emilio M., Erickson C., Evans R.,
Fabrega-Polleri J., Garcia-Lambas D., Giacchini B.L., Hanna W., Herald D.,
Hesler G., Hinse T.C., Jacques C., Jehin E., Jorgensen U.G., Kerr S.,
Kouprianov V., Levine S.E., Linder T., Maley P.D., Machado D.I., Maquet L.,
Maury A., Melia R., Meza E., Mondon B., Moura T., Newman J., Payet T.,
Pereira C.L., Pollock J., Poltronieri R.C., Quispe-Huaynasi F., Reichart D.,
de Santana T., Schneiter E.M., Sieyra M.V., Skottfelt J., Soulier J.F.,
Starck M., Thierry P., Torres P.J., Trabuco L.L., Unda-Sanzana E.,
Yamashita T.A.R., Winter O.C., Zapata A., Zuluaga C.A.
<Astron. Astrophys. 652, A141 (2021)>
=2021A&A...652A.141M 2021A&A...652A.141M (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets ; Occultations
Keywords: occultations - methods: observational - methods: data analysis -
minor planets, asteroids: individual: Chariklo -
planets and satellites: rings
Abstract:
The Centaur (10199) Chariklo has the first rings system discovered
around a small object. It was first observed using stellar occultation
in 2013. Stellar occultations allow the determination of sizes and
shapes with kilometre accuracy and obtain characteristics of the
occulting object and its vicinity. Using stellar occultations observed
between 2017 and 2020, we aim at constraining Chariklo's and its rings
physical parameters. We also determine the rings' structure, and
obtain precise astrometrical positions of Chariklo. We predicted and
organised several observational campaigns of stellar occultations by
Chariklo. Occultation light curves were measured from the data sets,
from which ingress and egress times, and rings' width and opacity were
obtained. These measurements, combined with results from previous
works, allow us to obtain significant constraints on Chariklo's shape
and rings' structure. We characterise Chariklo's ring system (C1R and
C2R), and obtain radii and pole orientations that are consistent with,
but more accurate than, results from previous occultations. We
confirmed the detection of W-shaped structures within C1R and an
evident variation of radial width. The observed width ranges between
4.8 and 9.1km with a mean value of 6.5km. One dual observation
(visible and red) does not reveal any differences in the C1R opacity
profiles, indicating ring particle's size larger than a few microns.
The C1R ring eccentricity is found to be smaller than 0.022 (3-sigma),
and its width variations may indicate an eccentricity higher than
0.005. We fit a tri-axial shape to Chariklo's detections over eleven
occultations and determine that Chariklo is consistent with an
ellipsoid with semi-axes of 143.8, 135.2 and 99.1km. Ultimately, we
provided seven astrometric positions at a milliarcseconds accuracy
level, based on Gaia EDR3, and use it to improve Chariklo's ephemeris.
Description:
Table C1 contains the fitted parameters obtained for each stellar
occultation light curve with a positive detection of Chariklo or its
ring system. Table C2 contains the fitted ring parameters in the ring
plane obtained for each light curve.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablec1.dat 169 78 Fitted parameters obtained for each light curve
with a positive detection
tablec2.dat 127 54 Fitted ring parameters in the ring plane
obtained for each light curve
listlc.dat 52 43 List of light curves, including non-detections
lc/* . 43 Individual light curves
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Station Observational Station
21- 30 A10 "date" Date Date and time of the event (ISO)
32- 38 A7 --- Det Detection identification (1)
40- 51 A12 "h:m:s" Imm.Time Moment of star disappearance,
immersion time (ISO)
53- 57 F5.3 s e_Imm.Time Uncertainty on Imm.Time
59- 70 A12 "h:m:s" Em.Time Moment of star reappearance,
emersion time (ISO)
72- 76 F5.3 s e_Em.Time Uncertainty on Em.Time
78- 83 F6.3 s Dur Duration of the event
85- 89 F5.3 s E_Dur Error on Duration of the event (upper value)
91- 95 F5.3 s e_Dur Error on Duration of the event (lower value)
97-101 F5.3 --- Obl Apparent Oblatness
103-107 F5.3 --- E_Obl ? Error on Apparent Oblatness (upper value)
109-113 F5.3 --- e_Obl ? Error on Apparent Oblatness (lower value)
115-119 F5.3 --- chi2 Best fit Chi-Squared or
best fit Chi-Squared for immersion
121 A1 --- ---
123-127 F5.3 --- chi2em ? Best fit Chi-Squared for emersion
129-169 A41 --- FileName Name of the light curve file in
subdirectory lc
--------------------------------------------------------------------------------
Note (1): MB stands for the Main Body detections, C1R and C2R for the rings
detections. As each transit of the ring in front of the star is considered as
a detection, a given light curve may detect twice that ring (SNR allowing)
during a given event. For the main body occultations the apparent opacity was
not fitted and fixed as 1 (opaque body).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablec2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Station Observational Station
16- 25 A10 "date" Date Date and time of the event (ISO)
27- 29 A3 --- Ring Ring identification
31- 33 A3 --- Det Detection identification
35- 41 F7.3 km r Radial distance
43- 48 F6.3 km E_r Error on Radial distance (upper value)
50- 55 F6.3 km e_r Error on Radial distance (lower value)
57 A1 --- l_Wr Limit flag on Wr
58- 63 F6.3 km Wr Radial width of the ring
65- 70 F6.3 km E_Wr Error on Radial width of the ring
(upper value)
72- 77 F6.3 km e_Wr Error on Radial width of the ring
(lower value)
79- 83 F5.3 --- pN Normal opacity of the ring
85- 89 F5.3 --- E_pN Error on Normal opacity of the ring
(upper value)
92- 96 F5.3 --- e_pN Error on Normal opacity of the ring
(lower value)
98 A1 --- l_Ep Limit flag on Ep
99-104 F6.3 --- Ep Equivalent width of the ring
106-110 F5.3 --- E_Ep Error on Equivalent width of the ring
(upper value)
113-118 F6.3 --- e_Ep Error on Equivalent width of the ring
(lower value)
120-121 I2 --- N Number of point within each detection
123-127 F5.2 --- (1-phi0)/RMS Flux depth over light curve RMS
--------------------------------------------------------------------------------
Byte-by-byte Description of file: listlc.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Date Observation date
12- 52 A41 --- FileName Name of the light curve file in
subdirectory lc
--------------------------------------------------------------------------------
Byte-by-byte Description of file: lc/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 F16.8 d JD Julian date of observation
18- 28 F11.8 --- Fobs Normalised observed flux
30- 39 F10.8 --- Ffit Normalised fitted flux
--------------------------------------------------------------------------------
History:
From Bruno Morgado, morgado.fis(at)gmail.com
Acknowledgements:
We would like to thank D. Souami for her useful feedback, which
improved the quality of this manuscript. This work was carried out
within the "Lucky Star" umbrella that agglomerates the efforts of
the Paris, Granada and Rio teams, which is funded by the European
Research Council under the European Community's H2020 (ERC Grant
Agreement No. 669416). This research made use of SORA, a
python package for stellar occultations reduction and analysis,
developed with the support of ERC Lucky Star and LIneA/Brazil, within
the collaboration Rio-Paris-Granada teams. This work has made use of
data from the European Space Agency (ESA) mission Gaia
(https://www.cosmos.esa.int/gaia), processed by the Gaia Data
Processing and Analysis Consortium (DPAC,
https://www.cosmos.esa.int/web/gaia/dpac/consortium). Part of this
research is supported by INCT do e-Universo, Brazil (CNPQ grants
465376/2014-2). Based in part on observations made at the
Laboratorio Nacional de Astrofisica (LNA), Itajuba-MG, Brazil.
The data include observations taken by the MiNDSTEp team at the Danish
1.54m telescope at ESO's La Silla observatory and UGJ
acknowledges funding from the European Union H2020-MSCA-ITN-2019 under
grant no. 860470 (CHAMELEON) and from the Novo Nordisk Foundation
Interdisciplinary Synergy Programme grant no. NNF19OC0057374.
TRAPPIST-South is funded by the Belgian Fund for Scientific Research
(Fond National de la Recherche Scientifique, FNRS) under the grant PDR
T.0120.21. The authors acknowledge the use of Sonja Itting-Enke's
C14 telescope and the facilities at the Cuno Hoffmeister Memorial
Observatory (CHMO). The following authors acknowledge the respective
CNPq grants: BEM 150612/2020-6; FB-R 314772/2020-0; RV-M
304544/2017-f5, 401903/2016-8; JIBC 308150/2016-3 and 305917/2019-6;
MA 427700/2018-3, 310683/2017-3, 473002/2013-2. GBR acknowledges
CAPES-FAPERJ/PAPDRJ grant E26/203.173/2016 and CAPES-PRINT/UNESP grant
88887.571156/2020-00, MA FAPERJ grant E-26/111.488/2013 and ARGJr
FAPESP grant 2018/11239-8. J.L.O., P.S-S., R.D., and N.M. acknowledge
financial support from the State Agency for Research of the Spanish
MCIU through the "Center of Excellence Severo Ochoa" award to the
Instituto de Astrofisica de Andalucia (SEV-2017-0709), from Spanish
project AYA2017-89637-R, and from FEDER. P.S-S. acknowledges financial
support by the Spanish grant AYA-RTI2018-098657-J-I00 "LEO-SBNAF"
(MCIU/AEI/FEDER, UE). E. Jehin is a Belgian FNRS Senior Research
Associate. RS and OCW acknowledge FAPESP grant 2016/24561-0 and CNPq
grant 305210/2018-1. TCH acknowledges financial support from the
National Research Foundation (NRF; No. 2019R1I1A1A01059609).
(End) Patricia Vannier [CDS] 16-Aug-2021