General Question Which SidRotPeriod of Nereid is more correct?

[SuprunP]

I've got two Nereid.cfg files.
One of them is the original file from Orbiter 2010:

; === Configuration file for moon Nereid(Neptune) ===
Name = Nereid
EllipticOrbit = TRUE           ; assume unperturbed orbit
HasElements = TRUE             ; orbital elements follow

; === Planetary Mean Orbits ===
;***cfgBatchDataCalculator
Epoch =  2006.49555099247
SemiMajorAxis =  5515375933.0092
Eccentricity =  .747077257017379
Inclination =  8.85104685561022E-02
LongAscNode =  5.58688506093214
LongPerihelion =  10.7610359309656
MeanLongitude =  11.9389813216087



; === Physical Parameters ===
Mass = 1.317e19			 ; Approx. Calculated using Phoebe's Density
Size = 165e3
[B][COLOR="#ff0000"]SidRotPeriod = 41472.0 [/COLOR][/B]          ; by Chode
SidRotOffset = 0
Obliquity = 0.51452              ; inherit from Neptune
LAN = 2.29898                    ; inherit from Neptune
AlbedoRGB = 0.17 0.16 0.17       ; by VF2_Rolf

; === Visualisation Parameters ===
MaxPatchResolution = 4

The second one lists the following:

; === Configuration file for moon Nereid(Neptune) by Rolf Keibel Carl Romanik and Tony Dunn===
Name = Nereid
EllipticOrbit = TRUE           ; assume unperturbed orbit
HasElements = TRUE             ; orbital elements follow

; === Planetary Mean Orbits ===
Epoch =  2006.64779710751
SemiMajorAxis =  5513815856.36752
Eccentricity =  .747523782102472
Inclination =  8.84398637057097E-02
LongAscNode =  5.57496788610836
LongPerihelion =  10.7602527589763
MeanLongitude =  12.9084455152095

; === Physical Parameters ===
Mass = 1.317e19			 ; Approx. Calculated using Phoebe's Density
Size = 165e3
[B][COLOR="Red"]SidRotPeriod = 31116096	[/COLOR][/B]	 ; 360.14 days
SidRotOffset = 0
Obliquity = 0.51452              ; inherit from Neptune
LAN = 2.29898                    ; inherit from Neptune
AlbedoRGB = 0.17 0.16 0.17

; === Visualisation Parameters ===
MaxPatchResolution = 4

I have highlighted the dubious 'SidRotPeriod' parameter .
Which one is true?

Thanks.

 

[orb]

SidRotPeriod is sidereal rotation period around its own rotation axis, so more correct in this case is 41472.0 seconds than 31116096 seconds, which is its orbital rotation period.

According to Wikipedia the rotation period of Nereid is 0.48 d (11 h 31 min) - 41460 seconds. And additionally:

In 1991 a rotation period of Nereid of about 13.6 hours was determined by analysis the moon's light curve. Later in 2003 another rotation period of about 11.52 ± 0.14 hours was measured. However this determination was later disputed. Other researchers have failed so far to detect any periodic modulation in Nereid's light curve.

Additionally, if you're more interested -

Tommy Grav, Matthew J. Holman, and J. J. Kavelaars: The Short Rotation Period of Nereid​