J/MNRAS/462/1351 Outer satellites occultation predictions (Gomes-Junior+, 2016)
New orbits of irregular satellites designed for the predictions of stellar
occultations up to 2020, based on thousands of new observations.
Gomes-Junior A.R., Assafin M., Beauvalet L., Desmars J.,
Vieira-Martins R., Camargo J.I.B., Morgado B.E., Braga-Ribas F.
<Mon. Not. R. Astron. Soc. 462, 1351 (2016)>
=2016MNRAS.462.1351G 2016MNRAS.462.1351G (SIMBAD/NED BibCode)
ADC_Keywords: Positional data - Solar system
Keywords: ephemerides - occultations - planets and satellites: general -
planets and satellites: individual:
Jovian and Saturnian irregular satellites
Abstract:
Gomes-Junior et al. (2015, Cat. J/A+A/580/A76) published 3613
positions for the 8 largest irregular satellites of Jupiter and 1787
positions for the largest irregular satellite of Saturn, Phoebe. These
observations were made between 1995 and 2014 and have an estimated
error of about 60 to 80 mas. Based on this set of positions, we
derived new orbits for the eight largest irregular satellites of
Jupiter: Himalia, Elara, Pasiphae, Carme, Lysithea, Sinope, Ananke and
Leda. For Phoebe we updated the ephemeris from Desmars et al. (2013,
Cat. J/A+A/553/A36) using 75% more positions than the previous one.
Due to their orbital characteristics, it is common belief that the
irregular satellites were captured by the giant planets in the early
Solar System, but there is no consensus for a single model explaining
where they were formed. Size, shape, albedo and composition would help
to trace back their true origin, but these physical parameters are yet
poorly known for irregular satellites. The observation of stellar
occultations would allow for the determination of such parameters.
Indeed Jupiter will cross the galactic plane in 2019-2020 and Saturn
in 2018, improving a lot the chances of observing such events in the
near future. Using the derived ephemerides and the UCAC4 catalogue we
managed to identify 5442 candidate stellar occultations between
January 2016 and December 2020 for the 9 satellites studied here. We
discussed how the successful observation of a stellar occultation by
these objects is possible and present some potential occultations.
Description:
Tables contain the day of the year and UTC central instant of the
prediction; right ascension and declination of the occulted star - at
the central instant of the occultation (corrected by proper motions);
C/A: apparent geocentric distance between the satellite and the star
(a.k.a. the distance between the shadow and the center of the Earth)
at the moment of the geocentric closest approach, in arcseconds;
P/A: the satellite position angle with respect to the occulted star at
C/A, in degrees (zero at north of the star, increasing clockwise);
v: relative velocity of event in km/s: positive = prograde,
negative = retrograde; D: Geocentric distance to the occulting object
in AU; R*: normalized UCAC4 magnitude in the R-band to a common shadow
of 20km/s by the relationship R*=RUCAC4+2.5xlog(velocity/(20km/s)),
the value 20km/s is typical of events around the opposition; long:
east longitude of subplanet point in degrees, positive towards east,
at the instant of the geocentric closest approach; LST: UT + long:
local solar time at subplanet point, hh:mm; pm_ra and pm_dec: proper
motions in right ascension and declination, respectively (mas/year).
For more detailed information about the definition and use of these
stellar occultation geometric elements see Assafin et al. (2010, Cat.
J/A+A/515/A32).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 68 45 List of occultation catalogs
tables/* . 45 Individual tables of occultation
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See also:
J/A+A/515/A32 : Pluto, Charon, Nix, Hydra occultations 2008-15 (Assafin+, 2010)
J/A+A/553/A36 : Catalogue of Observations of Phoebe (Desmars+, 2013)
J/A+A/580/A76 : Positions of satellites of giant planets (Gomes-Junior+, 2015)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Satellite name
10- 13 I4 yr Year Year for predicted occultations
15- 27 A13 --- FileName Name of the file with occultation predictions
in subdirectory tables
29- 68 A40 --- Title Title of the file
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Byte-by-byte Description of file: tables/*
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Bytes Format Units Label Explanations
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2- 3 I2 d Occ.D Day of Occultation
5- 6 I2 "month" Occ.M Month of Occultation
8- 11 I4 yr Occ.Y Year of Occultation
13- 14 I2 h Occ.h Hour of Occultation
16- 17 I2 min Occ.m Month of Occultation
19- 20 I2 s Occ.s Second of Occultation
22- 23 I2 h RAh Right ascension (J2000.0) (1)
25- 26 I2 min RAm Right ascension (J2000.0) (1)
28- 34 F7.4 s RAs Right ascension (J2000.0) (1)
36 A1 --- DE- Sign of declination (J2000) (1)
37- 38 I2 deg DEd Declination (J2000.0) (1)
40- 41 I2 arcmin DEm Declination (J2000.0) (1)
43- 49 F7.4 arcsec DEs Declination (J2000.0) (1)
51- 55 F5.3 arcsec CA Closest Approach Distance (2)
57- 62 F6.2 deg PA Position angle with respect to the occulted
star at CA (zero at north of the star,
increasing clockwise)
64- 69 F6.2 km/s vel Relative velocity of event (3)
71- 75 F5.2 AU Dist Geocentric distance to the occulting object
77- 80 F4.1 mag Rmag Normalized UCAC4 magnitude in the R-band (4)
82- 84 I3 deg long East longitude of subplanet point (positive
towards east) at the instant of the
geocentric closest approach
86- 90 A5 "h:m" loc Local solar time at subplanet point
92- 95 I4 mas/yr pmRA Proper motion in Right Ascension (RA*cosDE)
97-100 I4 mas/yr pmDE Proper motion in Declination
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Note (1): Positions of the occulted star at the central instant of the
occultation (corrected by proper motions).
Note (2): apparent geocentric distance between the satellite and the star
(a.k.a. the distance between the shadow and the center of the Earth) at the
moment of the geocentric closest approach.
Note (3): relative velocity of event: positive = prograde, negative = retrograde
Note (4): Normalized UCAC4 magnitude in the R-band to a common shadow of
20km/s by the relationship R*=RUCAC4+2.5xlog(velocity/(20km/s)),
the value 20km/s is typical of events around the opposition.
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Acknowledgements:
Altair Ramos Gomes-Junior, altair08(at)astro.ufrj.br
(End) A.R. Gomes-Junior [UFRJ/OV, Brazil], P. Vannier [CDS] 21-Jul-2016