Nereid from space: Rotation, size and shape analysis from K2, Herschel and Spitzer observations

In this paper, we present an analysis of K2 mission Campaign 3 observations of the irregular Neptune satellite, Nereid. We determined a rotation period of P = 11.594±0.017 h and amplitude of Δm = 0.0328m ± 0.0018m, confirming previous short rotation periods obtained in ground-based observations. The similarities of light-curve amplitudes between 2001 and 2015 show that Nereid is in a low-amplitude rotation state nowadays and it could have been in a high-amplitude rotation state in the mid-1960s. Another high-amplitude period is expected in about 30 yr. Based on the light-curve amplitudes observed in the last 15 yr, we could constrain the shape of Nereid and obtained a maximum a:c axis ratio of 1.3:1. This excludes the previously suggested very elongated shape of a:c ≈ 1.9:

[1]  F. Henry,et al.  “TNOs are Cool”: A survey of the trans-Neptunian region , 2010, Astronomy & Astrophysics.

[2]  L. Kiss,et al.  PUSHING THE LIMITS: K2 OBSERVATIONS OF THE TRANS-NEPTUNIAN OBJECTS 2002 GV31 and (278361) 2007 JJ43 , 2015, 1504.03671.

[3]  L. Kiss,et al.  MAIN-BELT ASTEROIDS IN THE K2 ENGINEERING FIELD OF VIEW , 2015, 1501.05967.

[4]  E. Lellouch,et al.  THE ALBEDO–COLOR DIVERSITY OF TRANSNEPTUNIAN OBJECTS , 2014, 1406.1420.

[5]  F. Mullally,et al.  The K2 Mission: Characterization and Early Results , 2014, 1402.5163.

[6]  P. Hartogh,et al.  Optimized Herschel/PACS photometer observing and data reduction strategies for moving solar system targets , 2013 .

[7]  Michael Mommert,et al.  “TNOs are Cool”: A survey of the trans-Neptunian region - IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations , 2013 .

[8]  N. Abel,et al.  AN INVESTIGATION OF THE RELATIONSHIP BETWEEN SHAPE AND ROTATION TO EXPLAIN THE LIGHT CURVE OF NEREID , 2013 .

[9]  Y. Itoh,et al.  High-Precision Measurements of the Brightness Variation of Nereid , 2012, 1212.0597.

[10]  Michael Mueller,et al.  TNO Diameters And Albedos: The Final MIPS Dataset , 2012 .

[11]  Marc William Buie,et al.  Physical properties of trans-neptunian binaries (120347) Salacia-Actaea and (42355) Typhon-Echidna , 2012 .

[12]  András Pál,et al.  fitsh– a software package for image processing , 2011 .

[13]  P. Thomas.  Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission , 2010 .

[14]  S. Ott,et al.  Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy , 2010, 1005.5331.

[15]  D. A. Caldwell,et al.  INITIAL CHARACTERISTICS OF KEPLER SHORT CADENCE DATA , 2009, 1001.0142.

[16]  Robert A. Jacobson,et al.  THE ORBITS OF THE NEPTUNIAN SATELLITES AND THE ORIENTATION OF THE POLE OF NEPTUNE , 2008 .

[17]  B. Schaefer,et al.  Nereid: Light curve for 1999–2006 and a scenario for its variations , 2008, 0804.2835.

[18]  B. Buratti,et al.  BVR photometry of Hyperion near the time of the 2005 Cassini encounter , 2008 .

[19]  Thomas Henning,et al.  The Photodetector Array Camera and Spectrometer (PACS) for the Herschel Space Observatory , 2004, Astronomical Telescopes + Instrumentation.

[20]  Dale P. Cruikshank,et al.  The solar system beyond Neptune , 2008 .

[21]  J. Burns,et al.  Hyperion's sponge-like appearance , 2007, Nature.

[22]  B. Schaefer,et al.  The Diverse Solar Phase Curves of Distant Icy Bodies. I. Photometric Observations of 18 Trans-Neptunian Objects, 7 Centaurs, and Nereid , 2006, astro-ph/0605745.

[23]  Paul S. Smith,et al.  The Multiband Imaging Photometer for Spitzer (MIPS) , 2004 .

[24]  J. Burns,et al.  Discovery of five irregular moons of Neptune , 2004, Nature.

[25]  T. Grav,et al.  Photometry of Irregular Satellites of Uranus and Neptune , 2004, astro-ph/0405605.

[26]  T. Grav,et al.  The Short Rotation Period of Nereid , 2003, astro-ph/0306001.

[27]  J. Munn,et al.  The USNO-B Catalog , 2002, astro-ph/0210694.

[28]  Thomas Müller,et al.  Asteroids as calibration standards in the thermal infrared for space observatories , 2002 .

[29]  Alan W. Harris,et al.  A Thermal Model for Near-Earth Asteroids , 1998 .

[30]  A. Dobrovolskis,et al.  Chaotic Rotation of Nereid , 1995 .

[31]  David Jewitt,et al.  The Solar System Beyond Neptune , 1995 .

[32]  J. Veverka,et al.  VOYAGER OBSERVATIONS OF NEREID , 1991 .

[33]  J. Spencer.  A rough-surface thermophysical model for airless planets , 1990 .

[34]  L. Lebofsky,et al.  Systematic biases in radiometric diameter determinations , 1989 .