Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-04-17
Astronomy and Astrophysics
Astrophysics
Icarus in press, 45 manuscript pages
Scientific paper
10.1016/j.icarus.2008.02.025
Nereid is a small irregular moon of Neptune that displays large-, moderate-, and small-amplitude photometric variations on both fast and slow time scales. The central mystery of Nereid is now to explain the physical mechanism of these unique brightness changes and why they change with time. To characterize Nereid's variability, we have been using the SMARTS telescopes on Cerro Tololo for synoptic monitoring from 1999 to 2006. We present a well-sampled photometric time series of 493 magnitudes on 246 nights mostly in the V-band. In combination with our earlier data (for 774 magnitudes over 362 nights), our 20-year data set is the most comprehensive for any small icy body in our Solar System. Our yearly light curves show that Nereid displays various types of behaviors: large amplitude brightenings and fadings (1987 to 1990); moderate-amplitude variation about the average phase curve (1993-1997, 2003, 2005), moderate-amplitude variation and systematically brighter by roughly one-quarter magnitude throughout the entire season (2004); and nearly constant light curves superimposed on a surprisingly large-amplitude opposition surge (1998, 1999, 2000, 2006). Other than in 2004, Nereid's variations were closely centered around a constant phase curve that is well fit with a Hapke model for the coherent backscattering opposition surge mechanism with angular scale of 0.7+-0.1 degrees. In our entire data set from 1987-2006, we find no significant periodicity. We propose that the year-to-year changes in the variability of Nereid are caused by forced precession (caused by tidal forces from Neptune) on the spin axis of a nonspherical Nereid, such that cross-sectional areas and average albedos change as viewed from Earth.
Rabinowitz David L.
Schaefer Bradley E.
Schaefer Martha W.
Tourtellotte Suzanne W.
No associations
LandOfFree
Nereid: Light Curve for 1999-2006 and a Scenario for its Variations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Nereid: Light Curve for 1999-2006 and a Scenario for its Variations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nereid: Light Curve for 1999-2006 and a Scenario for its Variations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-507058