Physical Characterization of Active Asteroid (6478) Gault. (arXiv:1907.06643v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_J/0/1/0/all/0/1">Juan A. Sanchez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reddy_V/0/1/0/all/0/1">Vishnu Reddy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thirouin_A/0/1/0/all/0/1">Audrey Thirouin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wright_E/0/1/0/all/0/1">Edward L. Wright</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Linder_T/0/1/0/all/0/1">Tyler R. Linder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kareta_T/0/1/0/all/0/1">Theodore Kareta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sharkey_B/0/1/0/all/0/1">Benjamin Sharkey</a>

Main belt asteroid (6478) Gault has been dynamically linked with two
overlapping asteroid families: Phocaea, dominated by S-type asteroids, and
Tamara, dominated by low-albedo C-types. This object has recently become an
interesting case for study, after images obtained in late 2018 revealed that it
was active and displaying a comet-like tail. Previous authors have proposed
that the most likely scenarios to explain the observed activity on Gault were
rotational excitation or merger of near-contact binaries. Here we use new
photometric and spectroscopic data of Gault to determine its physical and
compositional properties. Lightcurves derived from the photometric data showed
little variation over three nights of observations, which prevented us from
determining the rotation period of the asteroid. Using WISE observations of
Gault and the near-Earth Asteroid Thermal Model (NEATM) we determined that this
asteroid has a diameter $<$6 km. NIR spectroscopic data obtained with the Infrared Telescope Facility (IRTF) showed a spectrum similar to that of S-complex asteroids, and a surface composition consistent with H chondrite meteorites. These results favor a compositional affinity between Gault and asteroid (25) Phocaea, and rules out a compositional link with the Tamara family. From the spectroscopic data we found no evidence of fresh material that could have been exposed during the outburst episodes.

Main belt asteroid (6478) Gault has been dynamically linked with two
overlapping asteroid families: Phocaea, dominated by S-type asteroids, and
Tamara, dominated by low-albedo C-types. This object has recently become an
interesting case for study, after images obtained in late 2018 revealed that it
was active and displaying a comet-like tail. Previous authors have proposed
that the most likely scenarios to explain the observed activity on Gault were
rotational excitation or merger of near-contact binaries. Here we use new
photometric and spectroscopic data of Gault to determine its physical and
compositional properties. Lightcurves derived from the photometric data showed
little variation over three nights of observations, which prevented us from
determining the rotation period of the asteroid. Using WISE observations of
Gault and the near-Earth Asteroid Thermal Model (NEATM) we determined that this
asteroid has a diameter $<$6 km. NIR spectroscopic data obtained with the
Infrared Telescope Facility (IRTF) showed a spectrum similar to that of
S-complex asteroids, and a surface composition consistent with H chondrite
meteorites. These results favor a compositional affinity between Gault and
asteroid (25) Phocaea, and rules out a compositional link with the Tamara
family. From the spectroscopic data we found no evidence of fresh material that
could have been exposed during the outburst episodes.

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