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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 (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:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 68 45 List of occultation catalogs tables/* 100 45 Individual tables of occultation
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
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: tables/*
Bytes Format Units Label Explanations
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
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.
Acknowledgements: Altair Ramos Gomes-Junior, altair08(at)astro.ufrj.br
(End) A.R. Gomes-Junior [UFRJ/OV, Brazil], P. Vannier [CDS] 21-Jul-2016
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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