Active asteroid (6478) Gault: a blue Q-type surface below the dust?. (arXiv:1907.10077v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Marsset_M/0/1/0/all/0/1">Michael Marsset</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DeMeo_F/0/1/0/all/0/1">Francesca DeMeo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sonka_A/0/1/0/all/0/1">Adrian Sonka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Birlan_M/0/1/0/all/0/1">Mirel Birlan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Polishook_D/0/1/0/all/0/1">David Polishook</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burt_B/0/1/0/all/0/1">Brian Burt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Binzel_R/0/1/0/all/0/1">Richard P. Binzel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bus_S/0/1/0/all/0/1">Shelte J. Bus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thomas_C/0/1/0/all/0/1">Cristina Thomas</a>
We present near-infrared spectroscopy of the sporadically active asteroid
(6478) Gault collected on the 3 m NASA/Infrared Telescope Facility observatory
in late 2019 March/early April. Long-exposure imaging with the 0.5 m NEEMO T05
telescope and previously published data simultaneously monitored the asteroid
activity, providing context for our measurements. We confirm Gault is a
silicate-rich (Q- or S-type) object likely linked to the (25) Phocaea
collisional family. The asteroid exhibits substantial spectral variability over
the 0.75-2.45 $mu$m wavelength range, from unusual blue (s’=-13.5+/-1.1%
$mu$m-1 to typical red (s’=+9.1+/-1.2% $mu$m-1) spectral slope, that does not
seem to correlate with activity. Spectral comparisons with samples of ordinary
chondrite meteorites suggest that the blue color relates to the partial loss of
the asteroid dust regolith, exposing a fresh, dust-free material at its
surface. The existence of asteroids rotating close to rotational break-up limit
and having similar spectral properties as Gault further supports this
interpretation. Future spectroscopic observations of Gault, when the tails
dissipate, will help further testing of our proposed hypothesis.
We present near-infrared spectroscopy of the sporadically active asteroid
(6478) Gault collected on the 3 m NASA/Infrared Telescope Facility observatory
in late 2019 March/early April. Long-exposure imaging with the 0.5 m NEEMO T05
telescope and previously published data simultaneously monitored the asteroid
activity, providing context for our measurements. We confirm Gault is a
silicate-rich (Q- or S-type) object likely linked to the (25) Phocaea
collisional family. The asteroid exhibits substantial spectral variability over
the 0.75-2.45 $mu$m wavelength range, from unusual blue (s’=-13.5+/-1.1%
$mu$m-1 to typical red (s’=+9.1+/-1.2% $mu$m-1) spectral slope, that does not
seem to correlate with activity. Spectral comparisons with samples of ordinary
chondrite meteorites suggest that the blue color relates to the partial loss of
the asteroid dust regolith, exposing a fresh, dust-free material at its
surface. The existence of asteroids rotating close to rotational break-up limit
and having similar spectral properties as Gault further supports this
interpretation. Future spectroscopic observations of Gault, when the tails
dissipate, will help further testing of our proposed hypothesis.
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