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J/AJ/146/12      Occultations through Starun's C ring            (Hedman+, 2013)

Kronoseismology: using density waves in Saturn's C ring to probe the planet's interior. Hedman M.M., Nicholson P.D. <Astron. J., 146, 12 (2013)> =2013AJ....146...12H
ADC_Keywords: Planets ; Occultations Keywords: planets and satellites: interiors - planets and satellites: rings Abstract: Saturn's C ring contains multiple spiral patterns that appear to be density waves driven by periodic gravitational perturbations. In other parts of Saturn's rings, such waves are generated by Lindblad resonances with Saturn's various moons, but most of the wave-like C-ring features are not situated near any strong resonance with any known moon. Using stellar occultation data obtained by the Visual and Infrared Mapping Spectrometer on board the Cassini spacecraft, we investigate the origin of six unidentified C-ring waves located between 80900 and 87200km from Saturn's center. By measuring differences in the waves' phases among the different occultations, we are able to determine both the number of arms in each spiral pattern and the speeds at which these patterns rotate around the planet. We find that all six of these waves have between two and four arms and pattern speeds between 1660°/day and 1861°/day. These speeds are too large to be attributed to any satellite resonance. Instead, they are comparable to the predicted pattern speeds of waves generated by low-order normal-mode oscillations within the planet. The precise pattern speeds associated with these waves should therefore provide strong constraints on Saturn's internal structure. Furthermore, we identify multiple waves with the same number of arms and very similar pattern speeds, indicating that multiple m=3 and m=2 sectoral (l=m) modes may exist within the planet. Description: Between 2005 and 2009, Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini spacecraft obtained a total of 27 occultation cuts through the C ring with sufficient signal-to-noise and spatial resolution to discern the relevant waves. The VIMS instrument is described in detail in Brown et al. (2004SSRv..115..111B). Using stellar occultation we investigate the origin of six unidentified C-ring waves located between 80900 and 87200km from Saturn's center. We have between 100 and 260 δφ estimates for each of the waves (Table5). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars 31 8 Stars in the occultation pairs table5.dat 58 1158 Time, longitude, and phase differences used to determine pattern speeds
See also: J/A+A/493/1183 : Saturn major satellites observations (1874-2007) (Desmars+, 2009) J/AJ/136/2214 : Positions of Saturn and its satellites in 2002-2006 (Peng+, 2008) J/A+A/485/293 : Events of Saturn satellites during 2009 equinox (Arlot+, 2008) J/A+A/422/377 : 1997-2000 Saturn's satellites astrometry (Qiao+, 2004) J/A+A/383/1054 : Astrometry of Pluto and Saturn in 1995-2001 (Rapaport+, 2002) J/A+A/383/296 : Saturnian Satellites positions (1996-2000) (Peng+, 2002) J/A+A/380/727 : 1995 Saturnian satellite observations (Vienne+, 2001) J/A+AS/139/47 : 1995 Saturnian satellites mutual events (Emelianov+, 1999) J/A+AS/139/305 : Position of Saturn's satellites (1982-1988) (Veiga+, 1999) J/A+AS/136/257 : Saturn's satellites in 1995/97 (Harper+ 1999) J/A+AS/121/65 : 1990-1994 Saturn's satellites astrometry (Harper+ 1997) J/AJ/103/983 : Stellar occultation candidates of Saturn (Bosh+, 1992) Byte-by-byte Description of file: stars
Bytes Format Units Label Explanations
1- 7 A7 --- Name Name of the star 9- 10 I2 h RAh Hour of Right Ascension (J2000) (1) 12- 13 I2 min RAm Minute of Right Ascension (J2000) (1) 15- 19 F5.2 s RAs Second of Right Ascension (J2000) (1) 21 A1 --- DE- Sign of the Declination (J2000) (1) 22- 23 I2 deg DEd Degree of Declination (J2000) (1) 25- 26 I2 arcmin DEm Arcminute of Declination (J2000) (1) 28- 31 F4.1 arcsec DEs Arcsecond of Declination (J2000) (1)
Note (1): Positions from SIMBAD database (; added at CDS)
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1 A1 --- --- [W] 2- 6 F5.2 Mm Wave Wave designation (1) 8- 14 A7 --- Name1 Name of the first star in the occultation pair (2) 15- 17 I03 --- Rev1 First "Rev" number of the occultation pair (3) 18 A1 --- C1 [ie] Cut obtained during ingress (i) or egress (e) 19 A1 --- --- [-] 21- 27 A7 --- Name2 Name of second star in the occultation pair (2) 28- 30 I03 --- Rev2 Second "Rev" number of the occultation pair (3) 31 A1 --- n_Rev2 [ie] Cut obtained during ingress (i) or egress (e) 33- 41 F9.5 d dt Observed time difference δt 43- 47 F5.1 deg dl Observed longitude difference δλ 49- 53 F5.1 deg dphi Phase difference δφ between waves 55- 58 F4.1 deg e_dphi Standard deviation of the phase difference
Note (1): The radial location of the inward-propagating wave in thousands of kilometers. Note (2): RCas (=R Cas), RSCnc (=RS Cnc), alpAur (=α Aur), alpSco (=α Sco), betGru (=β Gru), betPeg (=β Peg), gamCru (=γ Cru), RHya (=R Hya). Note (3): Cassini's orbit around Saturn (when the data were obtained).
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 05-Jun-2014
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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